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authorIan Wisbon <ian.wisbon@timesys.com>2011-02-15 15:53:51 -0500
committerIan Wisbon <ian.wisbon@timesys.com>2011-02-15 15:53:51 -0500
commitdfdbf3f6e2d279f2a46ed95614cb4bf07657394d (patch)
tree2cc05669c5d3e47f7d4b28e31076b6dc6e771f36 /drivers/mtd/nand/gpmi-nfc/gpmi-nfc-hal-common.c
parenteffff5718c380983788fe6c380671c18e15ac7c2 (diff)
Digi del-5.6 Complete2.6.31-digi-201102151558
Diffstat (limited to 'drivers/mtd/nand/gpmi-nfc/gpmi-nfc-hal-common.c')
-rw-r--r--drivers/mtd/nand/gpmi-nfc/gpmi-nfc-hal-common.c1037
1 files changed, 1037 insertions, 0 deletions
diff --git a/drivers/mtd/nand/gpmi-nfc/gpmi-nfc-hal-common.c b/drivers/mtd/nand/gpmi-nfc/gpmi-nfc-hal-common.c
new file mode 100644
index 000000000000..b38d653a21fd
--- /dev/null
+++ b/drivers/mtd/nand/gpmi-nfc/gpmi-nfc-hal-common.c
@@ -0,0 +1,1037 @@
+/*
+ * Freescale GPMI NFC NAND Flash Driver
+ *
+ * Copyright (C) 2010 Freescale Semiconductor, Inc.
+ * Copyright (C) 2008 Embedded Alley Solutions, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "gpmi-nfc.h"
+
+/**
+ * gpmi_nfc_bch_isr - BCH interrupt service routine.
+ *
+ * @interrupt_number: The interrupt number.
+ * @cookie: A cookie that contains a pointer to the owning device
+ * data structure.
+ */
+irqreturn_t gpmi_nfc_bch_isr(int irq, void *cookie)
+{
+ struct gpmi_nfc_data *this = cookie;
+ struct nfc_hal *nfc = this->nfc;
+
+ gpmi_nfc_add_event("> gpmi_nfc_bch_isr", 1);
+
+ /* Clear the interrupt. */
+
+ nfc->clear_bch(this);
+
+ /* Release the base level. */
+
+ complete(&(nfc->bch_done));
+
+ /* Return success. */
+
+ gpmi_nfc_add_event("< gpmi_nfc_bch_isr", -1);
+
+ return IRQ_HANDLED;
+
+}
+
+/**
+ * gpmi_nfc_dma_isr - DMA interrupt service routine.
+ *
+ * @interrupt_number: The interrupt number.
+ * @cookie: A cookie that contains a pointer to the owning device
+ * data structure.
+ */
+irqreturn_t gpmi_nfc_dma_isr(int irq, void *cookie)
+{
+ struct gpmi_nfc_data *this = cookie;
+ struct nfc_hal *nfc = this->nfc;
+
+ gpmi_nfc_add_event("> gpmi_nfc_dma_isr", 1);
+
+ /* Acknowledge the DMA channel's interrupt. */
+
+ mxs_dma_ack_irq(nfc->isr_dma_channel);
+
+ /* Release the base level. */
+
+ complete(&(nfc->dma_done));
+
+ /* Return success. */
+
+ gpmi_nfc_add_event("< gpmi_nfc_dma_isr", -1);
+
+ return IRQ_HANDLED;
+
+}
+
+/**
+ * gpmi_nfc_dma_init() - Initializes DMA.
+ *
+ * @this: Per-device data.
+ */
+int gpmi_nfc_dma_init(struct gpmi_nfc_data *this)
+{
+ struct device *dev = this->dev;
+ struct nfc_hal *nfc = this->nfc;
+ int i;
+ int error;
+
+ /* Allocate the DMA descriptors. */
+
+ for (i = 0; i < NFC_DMA_DESCRIPTOR_COUNT; i++) {
+ nfc->dma_descriptors[i] = mxs_dma_alloc_desc();
+ if (!nfc->dma_descriptors[i]) {
+ dev_err(dev, "Cannot allocate all DMA descriptors.\n");
+ error = -ENOMEM;
+ goto exit_descriptor_allocation;
+ }
+ }
+
+ /* If control arrives here, all is well. */
+
+ return 0;
+
+ /* Control arrives here when something has gone wrong. */
+
+exit_descriptor_allocation:
+ while (--i >= 0)
+ mxs_dma_free_desc(this->nfc->dma_descriptors[i]);
+
+ return error;
+
+}
+
+/**
+ * gpmi_nfc_dma_exit() - Shuts down DMA.
+ *
+ * @this: Per-device data.
+ */
+void gpmi_nfc_dma_exit(struct gpmi_nfc_data *this)
+{
+ struct nfc_hal *nfc = this->nfc;
+ int i;
+
+ /* Free the DMA descriptors. */
+
+ for (i = 0; i < NFC_DMA_DESCRIPTOR_COUNT; i++)
+ mxs_dma_free_desc(nfc->dma_descriptors[i]);
+
+}
+
+/**
+ * gpmi_nfc_set_geometry() - Shared NFC geometry configuration.
+ *
+ * In principle, computing the NFC geometry is version-specific. However, at
+ * this writing all, versions share the same page model, so this code can also
+ * be shared.
+ *
+ * @this: Per-device data.
+ */
+int gpmi_nfc_set_geometry(struct gpmi_nfc_data *this)
+{
+ struct device *dev = this->dev;
+ struct physical_geometry *physical = &this->physical_geometry;
+ struct nfc_geometry *geometry = &this->nfc_geometry;
+ struct boot_rom_helper *rom = this->rom;
+ unsigned int metadata_size;
+ unsigned int status_size;
+ unsigned int chunk_data_size_in_bits;
+ unsigned int chunk_ecc_size_in_bits;
+ unsigned int chunk_total_size_in_bits;
+ unsigned int block_mark_chunk_number;
+ unsigned int block_mark_chunk_bit_offset;
+ unsigned int block_mark_bit_offset;
+
+ /* At this writing, we support only BCH. */
+
+ geometry->ecc_algorithm = "BCH";
+
+ /*
+ * We always choose a metadata size of 10. Don't try to make sense of
+ * it -- this is really only for historical compatibility.
+ */
+
+ geometry->metadata_size_in_bytes = 10;
+
+ /*
+ * At this writing, we always use 512-byte ECC chunks. Later hardware
+ * will be able to support larger chunks, which will cause this
+ * decision to move into version-specific code.
+ */
+
+ geometry->ecc_chunk_size_in_bytes = 512;
+
+ /* Compute the page size based on the physical geometry. */
+
+ geometry->page_size_in_bytes =
+ physical->page_data_size_in_bytes +
+ physical->page_oob_size_in_bytes ;
+
+ /*
+ * Compute the total number of ECC chunks in a page. This includes the
+ * slightly larger chunk at the beginning of the page, which contains
+ * both data and metadata.
+ */
+
+ geometry->ecc_chunk_count =
+ physical->page_data_size_in_bytes /
+ /*---------------------------------*/
+ geometry->ecc_chunk_size_in_bytes;
+
+ /*
+ * We use the same ECC strength for all chunks, including the first one.
+ * At this writing, we base our ECC strength choice entirely on the
+ * the physical page geometry. In the future, this should be changed to
+ * pay attention to the detailed device information we gathered earlier.
+ */
+
+ geometry->ecc_strength = 0;
+
+ switch (physical->page_data_size_in_bytes) {
+ case 2048:
+ geometry->ecc_strength = 8;
+ break;
+ case 4096:
+ switch (physical->page_oob_size_in_bytes) {
+ case 128:
+ geometry->ecc_strength = 8;
+ break;
+ case 218:
+ geometry->ecc_strength = 16;
+ break;
+ }
+ break;
+ }
+
+ /* Check if we were able to figure out the ECC strength. */
+
+ if (!geometry->ecc_strength) {
+ dev_err(dev, "Unsupported page geometry: %u:%u\n",
+ physical->page_data_size_in_bytes,
+ physical->page_oob_size_in_bytes);
+ return !0;
+ }
+
+ /*
+ * The payload buffer contains the data area of a page. The ECC engine
+ * only needs what's required to hold the data.
+ */
+
+ geometry->payload_size_in_bytes = physical->page_data_size_in_bytes;
+
+ /*
+ * In principle, computing the auxiliary buffer geometry is NFC
+ * version-specific. However, at this writing, all versions share the
+ * same model, so this code can also be shared.
+ *
+ * The auxiliary buffer contains the metadata and the ECC status. The
+ * metadata is padded to the nearest 32-bit boundary. The ECC status
+ * contains one byte for every ECC chunk, and is also padded to the
+ * nearest 32-bit boundary.
+ */
+
+ metadata_size = (geometry->metadata_size_in_bytes + 0x3) & ~0x3;
+ status_size = (geometry->ecc_chunk_count + 0x3) & ~0x3;
+
+ geometry->auxiliary_size_in_bytes = metadata_size + status_size;
+ geometry->auxiliary_status_offset = metadata_size;
+
+ /* Check if we're going to do block mark swapping. */
+
+ if (!rom->swap_block_mark)
+ return 0;
+
+ /*
+ * If control arrives here, we're doing block mark swapping, so we need
+ * to compute the byte and bit offsets of the physical block mark within
+ * the ECC-based view of the page data. In principle, this isn't a
+ * difficult computation -- but it's very important and it's easy to get
+ * it wrong, so we do it carefully.
+ *
+ * Note that this calculation is simpler because we use the same ECC
+ * strength for all chunks, including the zero'th one, which contains
+ * the metadata. The calculation would be slightly more complicated
+ * otherwise.
+ *
+ * We start by computing the physical bit offset of the block mark. We
+ * then subtract the number of metadata and ECC bits appearing before
+ * the mark to arrive at its bit offset within the data alone.
+ */
+
+ /* Compute some important facts about chunk geometry. */
+
+ chunk_data_size_in_bits = geometry->ecc_chunk_size_in_bytes * 8;
+ chunk_ecc_size_in_bits = geometry->ecc_strength * 13;
+
+ chunk_total_size_in_bits =
+ chunk_data_size_in_bits + chunk_ecc_size_in_bits;
+
+ /* Compute the bit offset of the block mark within the physical page. */
+
+ block_mark_bit_offset = physical->page_data_size_in_bytes * 8;
+
+ /* Subtract the metadata bits. */
+
+ block_mark_bit_offset -= geometry->metadata_size_in_bytes * 8;
+
+ /*
+ * Compute the chunk number (starting at zero) in which the block mark
+ * appears.
+ */
+
+ block_mark_chunk_number =
+ block_mark_bit_offset / chunk_total_size_in_bits;
+
+ /*
+ * Compute the bit offset of the block mark within its chunk, and
+ * validate it.
+ */
+
+ block_mark_chunk_bit_offset =
+ block_mark_bit_offset -
+ (block_mark_chunk_number * chunk_total_size_in_bits);
+
+ if (block_mark_chunk_bit_offset > chunk_data_size_in_bits) {
+
+ /*
+ * If control arrives here, the block mark actually appears in
+ * the ECC bits of this chunk. This wont' work.
+ */
+
+ dev_err(dev, "Unsupported page geometry "
+ "(block mark in ECC): %u:%u\n",
+ physical->page_data_size_in_bytes,
+ physical->page_oob_size_in_bytes);
+ return !0;
+
+ }
+
+ /*
+ * Now that we know the chunk number in which the block mark appears,
+ * we can subtract all the ECC bits that appear before it.
+ */
+
+ block_mark_bit_offset -=
+ block_mark_chunk_number * chunk_ecc_size_in_bits;
+
+ /*
+ * We now know the absolute bit offset of the block mark within the
+ * ECC-based data. We can now compute the byte offset and the bit
+ * offset within the byte.
+ */
+
+ geometry->block_mark_byte_offset = block_mark_bit_offset / 8;
+ geometry->block_mark_bit_offset = block_mark_bit_offset % 8;
+
+ /* Return success. */
+
+ return 0;
+
+}
+
+/*
+ * This code is useful for debugging.
+ */
+
+/*#define DUMP_DMA_CONTEXT*/
+
+#if (defined DUMP_DMA_CONTEXT)
+
+int dump_dma_context_flag;
+
+void dump_dma_context(struct gpmi_nfc_data *this, char *title)
+{
+
+ struct resources *resources = &this->resources;
+ struct nfc_hal *nfc = this->nfc;
+ struct mxs_dma_desc **d = nfc->dma_descriptors;
+ void *q;
+ uint32_t *p;
+ unsigned int i;
+ unsigned int j;
+
+ if (!dump_dma_context_flag)
+ return;
+
+ pr_info("%s\n", title);
+ pr_info("======\n");
+ pr_info("\n");
+
+ /*--------------------------------------------------------------------*/
+
+ pr_info(" Descriptors\n");
+ pr_info(" -----------\n");
+ {
+
+ for (i = 0; i < NFC_DMA_DESCRIPTOR_COUNT; i++, d++) {
+ pr_info(" #%u\n", i);
+ pr_info(" --\n");
+ pr_info(" Physical Address: 0x%08x\n" , (*d)->address);
+ pr_info(" Next : 0x%08lx\n", (*d)->cmd.next);
+ pr_info(" Command : 0x%08lx\n", (*d)->cmd.cmd.data);
+ pr_info(" Buffer : 0x%08x\n" , (*d)->cmd.address);
+ for (j = 0; j < 6; j++)
+ pr_info(" PIO[%u] : 0x%08lx\n",
+ j, (*d)->cmd.pio_words[j]);
+ }
+
+ }
+ pr_info("\n");
+
+ /*--------------------------------------------------------------------*/
+
+ pr_info(" DMA\n");
+ pr_info(" ---\n");
+ {
+ void *DMA = IO_ADDRESS(APBH_DMA_PHYS_ADDR);
+
+ p = q = DMA + 0x200;
+
+ for (i = 0; i < 7; i++) {
+ pr_info(" [0x%03x] 0x%08x\n", q - DMA, *p);
+ q += 0x10;
+ p = q;
+ }
+
+ }
+ pr_info("\n");
+
+ /*--------------------------------------------------------------------*/
+
+ pr_info(" GPMI\n");
+ pr_info(" ----\n");
+ {
+ void *GPMI = resources->gpmi_regs;
+
+ p = q = GPMI;
+
+ for (i = 0; i < 33; i++) {
+ pr_info(" [0x%03x] 0x%08x\n", q - GPMI, *p);
+ q += 0x10;
+ p = q;
+ }
+
+ }
+ pr_info("\n");
+
+ /*--------------------------------------------------------------------*/
+
+ pr_info(" BCH\n");
+ pr_info(" ---\n");
+ {
+ void *BCH = resources->bch_regs;
+
+ p = q = BCH;
+
+ for (i = 0; i < 22; i++) {
+ pr_info(" [0x%03x] 0x%08x\n", q - BCH, *p);
+ q += 0x10;
+ p = q;
+ }
+
+ }
+ pr_info("\n");
+
+}
+
+#endif
+
+/**
+ * gpmi_nfc_dma_go - Run a DMA channel.
+ *
+ * @this: Per-device data structure.
+ * @dma_channel: The DMA channel we're going to use.
+ */
+int gpmi_nfc_dma_go(struct gpmi_nfc_data *this, int dma_channel)
+{
+ struct device *dev = this->dev;
+ struct resources *resources = &this->resources;
+ struct nfc_hal *nfc = this->nfc;
+ unsigned long timeout;
+ int error;
+ LIST_HEAD(tmp_desc_list);
+
+ gpmi_nfc_add_event("> gpmi_nfc_dma_go", 1);
+
+ /* Get ready... */
+
+ nfc->isr_dma_channel = dma_channel;
+ init_completion(&nfc->dma_done);
+ mxs_dma_enable_irq(dma_channel, 1);
+
+ /* Go! */
+
+ #if defined(DUMP_DMA_CONTEXT)
+ dump_dma_context(this, "BEFORE");
+ #endif
+
+ mxs_dma_enable(dma_channel);
+
+ /* Wait for it to finish. */
+
+ timeout = wait_for_completion_timeout(&nfc->dma_done,
+ msecs_to_jiffies(1000));
+
+ #if defined(DUMP_DMA_CONTEXT)
+ dump_dma_context(this, "AFTER");
+ #endif
+
+ error = (!timeout) ? -ETIMEDOUT : 0;
+
+ if (error) {
+ dev_err(dev, "[%s] Chip: %u, DMA Channel: %d, Error %d\n",
+ __func__, dma_channel - resources->dma_low_channel,
+ dma_channel, error);
+ gpmi_nfc_add_event("...DMA timed out", 0);
+ } else
+ gpmi_nfc_add_event("...Finished DMA successfully", 0);
+
+ /* Clear out the descriptors we just ran. */
+
+ mxs_dma_cooked(dma_channel, &tmp_desc_list);
+
+ /* Shut the DMA channel down. */
+
+ mxs_dma_reset(dma_channel);
+ mxs_dma_enable_irq(dma_channel, 0);
+ mxs_dma_disable(dma_channel);
+
+ /* Return. */
+
+ gpmi_nfc_add_event("< gpmi_nfc_dma_go", -1);
+
+ return error;
+
+}
+
+/**
+ * ns_to_cycles - Converts time in nanoseconds to cycles.
+ *
+ * @ntime: The time, in nanoseconds.
+ * @period: The cycle period, in nanoseconds.
+ * @min: The minimum allowable number of cycles.
+ */
+static unsigned int ns_to_cycles(unsigned int time,
+ unsigned int period, unsigned int min)
+{
+ unsigned int k;
+
+ /*
+ * Compute the minimum number of cycles that entirely contain the
+ * given time.
+ */
+
+ k = (time + period - 1) / period;
+
+ return max(k, min);
+
+}
+
+/**
+ * gpmi_compute_hardware_timing - Apply timing to current hardware conditions.
+ *
+ * @this: Per-device data.
+ * @hardware_timing: A pointer to a hardware timing structure that will receive
+ * the results of our calculations.
+ */
+int gpmi_nfc_compute_hardware_timing(struct gpmi_nfc_data *this,
+ struct gpmi_nfc_hardware_timing *hw)
+{
+ struct gpmi_nfc_platform_data *pdata = this->pdata;
+ struct physical_geometry *physical = &this->physical_geometry;
+ struct nfc_hal *nfc = this->nfc;
+ struct gpmi_nfc_timing target = nfc->timing;
+ bool improved_timing_is_available;
+ unsigned long clock_frequency_in_hz;
+ unsigned int clock_period_in_ns;
+ bool dll_use_half_periods;
+ unsigned int dll_delay_shift;
+ unsigned int max_sample_delay_in_ns;
+ unsigned int address_setup_in_cycles;
+ unsigned int data_setup_in_ns;
+ unsigned int data_setup_in_cycles;
+ unsigned int data_hold_in_cycles;
+ int ideal_sample_delay_in_ns;
+ unsigned int sample_delay_factor;
+ int tEYE;
+ unsigned int min_prop_delay_in_ns = pdata->min_prop_delay_in_ns;
+ unsigned int max_prop_delay_in_ns = pdata->max_prop_delay_in_ns;
+
+ /*
+ * If there are multiple chips, we need to relax the timings to allow
+ * for signal distortion due to higher capacitance.
+ */
+
+ if (physical->chip_count > 2) {
+ target.data_setup_in_ns += 10;
+ target.data_hold_in_ns += 10;
+ target.address_setup_in_ns += 10;
+ } else if (physical->chip_count > 1) {
+ target.data_setup_in_ns += 5;
+ target.data_hold_in_ns += 5;
+ target.address_setup_in_ns += 5;
+ }
+
+ /* Check if improved timing information is available. */
+
+ improved_timing_is_available =
+ (target.tREA_in_ns >= 0) &&
+ (target.tRLOH_in_ns >= 0) &&
+ (target.tRHOH_in_ns >= 0) ;
+
+ /* Inspect the clock. */
+
+ clock_frequency_in_hz = nfc->clock_frequency_in_hz;
+ clock_period_in_ns = 1000000000 / clock_frequency_in_hz;
+
+ /*
+ * The NFC quantizes setup and hold parameters in terms of clock cycles.
+ * Here, we quantize the setup and hold timing parameters to the
+ * next-highest clock period to make sure we apply at least the
+ * specified times.
+ *
+ * For data setup and data hold, the hardware interprets a value of zero
+ * as the largest possible delay. This is not what's intended by a zero
+ * in the input parameter, so we impose a minimum of one cycle.
+ */
+
+ data_setup_in_cycles = ns_to_cycles(target.data_setup_in_ns,
+ clock_period_in_ns, 1);
+ data_hold_in_cycles = ns_to_cycles(target.data_hold_in_ns,
+ clock_period_in_ns, 1);
+ address_setup_in_cycles = ns_to_cycles(target.address_setup_in_ns,
+ clock_period_in_ns, 0);
+
+ /*
+ * The clock's period affects the sample delay in a number of ways:
+ *
+ * (1) The NFC HAL tells us the maximum clock period the sample delay
+ * DLL can tolerate. If the clock period is greater than half that
+ * maximum, we must configure the DLL to be driven by half periods.
+ *
+ * (2) We need to convert from an ideal sample delay, in ns, to a
+ * "sample delay factor," which the NFC uses. This factor depends on
+ * whether we're driving the DLL with full or half periods.
+ * Paraphrasing the reference manual:
+ *
+ * AD = SDF x 0.125 x RP
+ *
+ * where:
+ *
+ * AD is the applied delay, in ns.
+ * SDF is the sample delay factor, which is dimensionless.
+ * RP is the reference period, in ns, which is a full clock period
+ * if the DLL is being driven by full periods, or half that if
+ * the DLL is being driven by half periods.
+ *
+ * Let's re-arrange this in a way that's more useful to us:
+ *
+ * 8
+ * SDF = AD x ----
+ * RP
+ *
+ * The reference period is either the clock period or half that, so this
+ * is:
+ *
+ * 8 AD x DDF
+ * SDF = AD x ----- = --------
+ * f x P P
+ *
+ * where:
+ *
+ * f is 1 or 1/2, depending on how we're driving the DLL.
+ * P is the clock period.
+ * DDF is the DLL Delay Factor, a dimensionless value that
+ * incorporates all the constants in the conversion.
+ *
+ * DDF will be either 8 or 16, both of which are powers of two. We can
+ * reduce the cost of this conversion by using bit shifts instead of
+ * multiplication or division. Thus:
+ *
+ * AD << DDS
+ * SDF = ---------
+ * P
+ *
+ * or
+ *
+ * AD = (SDF >> DDS) x P
+ *
+ * where:
+ *
+ * DDS is the DLL Delay Shift, the logarithm to base 2 of the DDF.
+ */
+
+ if (clock_period_in_ns > (nfc->max_dll_clock_period_in_ns >> 1)) {
+ dll_use_half_periods = true;
+ dll_delay_shift = 3 + 1;
+ } else {
+ dll_use_half_periods = false;
+ dll_delay_shift = 3;
+ }
+
+ /*
+ * Compute the maximum sample delay the NFC allows, under current
+ * conditions. If the clock is running too slowly, no sample delay is
+ * possible.
+ */
+
+ if (clock_period_in_ns > nfc->max_dll_clock_period_in_ns)
+ max_sample_delay_in_ns = 0;
+ else {
+
+ /*
+ * Compute the delay implied by the largest sample delay factor
+ * the NFC allows.
+ */
+
+ max_sample_delay_in_ns =
+ (nfc->max_sample_delay_factor * clock_period_in_ns) >>
+ dll_delay_shift;
+
+ /*
+ * Check if the implied sample delay larger than the NFC
+ * actually allows.
+ */
+
+ if (max_sample_delay_in_ns > nfc->max_dll_delay_in_ns)
+ max_sample_delay_in_ns = nfc->max_dll_delay_in_ns;
+
+ }
+
+ /*
+ * Check if improved timing information is available. If not, we have to
+ * use a less-sophisticated algorithm.
+ */
+
+ if (!improved_timing_is_available) {
+
+ /*
+ * Fold the read setup time required by the NFC into the ideal
+ * sample delay.
+ */
+
+ ideal_sample_delay_in_ns = target.gpmi_sample_delay_in_ns +
+ nfc->internal_data_setup_in_ns;
+
+ /*
+ * The ideal sample delay may be greater than the maximum
+ * allowed by the NFC. If so, we can trade off sample delay time
+ * for more data setup time.
+ *
+ * In each iteration of the following loop, we add a cycle to
+ * the data setup time and subtract a corresponding amount from
+ * the sample delay until we've satisified the constraints or
+ * can't do any better.
+ */
+
+ while ((ideal_sample_delay_in_ns > max_sample_delay_in_ns) &&
+ (data_setup_in_cycles < nfc->max_data_setup_cycles)) {
+
+ data_setup_in_cycles++;
+ ideal_sample_delay_in_ns -= clock_period_in_ns;
+
+ if (ideal_sample_delay_in_ns < 0)
+ ideal_sample_delay_in_ns = 0;
+
+ }
+
+ /*
+ * Compute the sample delay factor that corresponds most closely
+ * to the ideal sample delay. If the result is too large for the
+ * NFC, use the maximum value.
+ *
+ * Notice that we use the ns_to_cycles function to compute the
+ * sample delay factor. We do this because the form of the
+ * computation is the same as that for calculating cycles.
+ */
+
+ sample_delay_factor =
+ ns_to_cycles(
+ ideal_sample_delay_in_ns << dll_delay_shift,
+ clock_period_in_ns, 0);
+
+ if (sample_delay_factor > nfc->max_sample_delay_factor)
+ sample_delay_factor = nfc->max_sample_delay_factor;
+
+ /* Skip to the part where we return our results. */
+
+ goto return_results;
+
+ }
+
+ /*
+ * If control arrives here, we have more detailed timing information,
+ * so we can use a better algorithm.
+ */
+
+ /*
+ * Fold the read setup time required by the NFC into the maximum
+ * propagation delay.
+ */
+
+ max_prop_delay_in_ns += nfc->internal_data_setup_in_ns;
+
+ /*
+ * Earlier, we computed the number of clock cycles required to satisfy
+ * the data setup time. Now, we need to know the actual nanoseconds.
+ */
+
+ data_setup_in_ns = clock_period_in_ns * data_setup_in_cycles;
+
+ /*
+ * Compute tEYE, the width of the data eye when reading from the NAND
+ * Flash. The eye width is fundamentally determined by the data setup
+ * time, perturbed by propagation delays and some characteristics of the
+ * NAND Flash device.
+ *
+ * start of the eye = max_prop_delay + tREA
+ * end of the eye = min_prop_delay + tRHOH + data_setup
+ */
+
+ tEYE = (int)min_prop_delay_in_ns + (int)target.tRHOH_in_ns +
+ (int)data_setup_in_ns;
+
+ tEYE -= (int)max_prop_delay_in_ns + (int)target.tREA_in_ns;
+
+ /*
+ * The eye must be open. If it's not, we can try to open it by
+ * increasing its main forcer, the data setup time.
+ *
+ * In each iteration of the following loop, we increase the data setup
+ * time by a single clock cycle. We do this until either the eye is
+ * open or we run into NFC limits.
+ */
+
+ while ((tEYE <= 0) &&
+ (data_setup_in_cycles < nfc->max_data_setup_cycles)) {
+ /* Give a cycle to data setup. */
+ data_setup_in_cycles++;
+ /* Synchronize the data setup time with the cycles. */
+ data_setup_in_ns += clock_period_in_ns;
+ /* Adjust tEYE accordingly. */
+ tEYE += clock_period_in_ns;
+ }
+
+ /*
+ * When control arrives here, the eye is open. The ideal time to sample
+ * the data is in the center of the eye:
+ *
+ * end of the eye + start of the eye
+ * --------------------------------- - data_setup
+ * 2
+ *
+ * After some algebra, this simplifies to the code immediately below.
+ */
+
+ ideal_sample_delay_in_ns =
+ ((int)max_prop_delay_in_ns +
+ (int)target.tREA_in_ns +
+ (int)min_prop_delay_in_ns +
+ (int)target.tRHOH_in_ns -
+ (int)data_setup_in_ns) >> 1;
+
+ /*
+ * The following figure illustrates some aspects of a NAND Flash read:
+ *
+ *
+ * __ _____________________________________
+ * RDN \_________________/
+ *
+ * <---- tEYE ----->
+ * /-----------------\
+ * Read Data ----------------------------< >---------
+ * \-----------------/
+ * ^ ^ ^ ^
+ * | | | |
+ * |<--Data Setup -->|<--Delay Time -->| |
+ * | | | |
+ * | | |
+ * | |<-- Quantized Delay Time -->|
+ * | | |
+ *
+ *
+ * We have some issues we must now address:
+ *
+ * (1) The *ideal* sample delay time must not be negative. If it is, we
+ * jam it to zero.
+ *
+ * (2) The *ideal* sample delay time must not be greater than that
+ * allowed by the NFC. If it is, we can increase the data setup
+ * time, which will reduce the delay between the end of the data
+ * setup and the center of the eye. It will also make the eye
+ * larger, which might help with the next issue...
+ *
+ * (3) The *quantized* sample delay time must not fall either before the
+ * eye opens or after it closes (the latter is the problem
+ * illustrated in the above figure).
+ */
+
+ /* Jam a negative ideal sample delay to zero. */
+
+ if (ideal_sample_delay_in_ns < 0)
+ ideal_sample_delay_in_ns = 0;
+
+ /*
+ * Extend the data setup as needed to reduce the ideal sample delay
+ * below the maximum permitted by the NFC.
+ */
+
+ while ((ideal_sample_delay_in_ns > max_sample_delay_in_ns) &&
+ (data_setup_in_cycles < nfc->max_data_setup_cycles)) {
+
+ /* Give a cycle to data setup. */
+ data_setup_in_cycles++;
+ /* Synchronize the data setup time with the cycles. */
+ data_setup_in_ns += clock_period_in_ns;
+ /* Adjust tEYE accordingly. */
+ tEYE += clock_period_in_ns;
+
+ /*
+ * Decrease the ideal sample delay by one half cycle, to keep it
+ * in the middle of the eye.
+ */
+ ideal_sample_delay_in_ns -= (clock_period_in_ns >> 1);
+
+ /* Jam a negative ideal sample delay to zero. */
+ if (ideal_sample_delay_in_ns < 0)
+ ideal_sample_delay_in_ns = 0;
+
+ }
+
+ /*
+ * Compute the sample delay factor that corresponds to the ideal sample
+ * delay. If the result is too large, then use the maximum allowed
+ * value.
+ *
+ * Notice that we use the ns_to_cycles function to compute the sample
+ * delay factor. We do this because the form of the computation is the
+ * same as that for calculating cycles.
+ */
+
+ sample_delay_factor =
+ ns_to_cycles(ideal_sample_delay_in_ns << dll_delay_shift,
+ clock_period_in_ns, 0);
+
+ if (sample_delay_factor > nfc->max_sample_delay_factor)
+ sample_delay_factor = nfc->max_sample_delay_factor;
+
+ /*
+ * These macros conveniently encapsulate a computation we'll use to
+ * continuously evaluate whether or not the data sample delay is inside
+ * the eye.
+ */
+
+ #define IDEAL_DELAY ((int) ideal_sample_delay_in_ns)
+
+ #define QUANTIZED_DELAY \
+ ((int) ((sample_delay_factor * clock_period_in_ns) >> \
+ dll_delay_shift))
+
+ #define DELAY_ERROR (abs(QUANTIZED_DELAY - IDEAL_DELAY))
+
+ #define SAMPLE_IS_NOT_WITHIN_THE_EYE (DELAY_ERROR > (tEYE >> 1))
+
+ /*
+ * While the quantized sample time falls outside the eye, reduce the
+ * sample delay or extend the data setup to move the sampling point back
+ * toward the eye. Do not allow the number of data setup cycles to
+ * exceed the maximum allowed by the NFC.
+ */
+
+ while (SAMPLE_IS_NOT_WITHIN_THE_EYE &&
+ (data_setup_in_cycles < nfc->max_data_setup_cycles)) {
+
+ /*
+ * If control arrives here, the quantized sample delay falls
+ * outside the eye. Check if it's before the eye opens, or after
+ * the eye closes.
+ */
+
+ if (QUANTIZED_DELAY > IDEAL_DELAY) {
+
+ /*
+ * If control arrives here, the quantized sample delay
+ * falls after the eye closes. Decrease the quantized
+ * delay time and then go back to re-evaluate.
+ */
+
+ if (sample_delay_factor != 0)
+ sample_delay_factor--;
+
+ continue;
+
+ }
+
+ /*
+ * If control arrives here, the quantized sample delay falls
+ * before the eye opens. Shift the sample point by increasing
+ * data setup time. This will also make the eye larger.
+ */
+
+ /* Give a cycle to data setup. */
+ data_setup_in_cycles++;
+ /* Synchronize the data setup time with the cycles. */
+ data_setup_in_ns += clock_period_in_ns;
+ /* Adjust tEYE accordingly. */
+ tEYE += clock_period_in_ns;
+
+ /*
+ * Decrease the ideal sample delay by one half cycle, to keep it
+ * in the middle of the eye.
+ */
+ ideal_sample_delay_in_ns -= (clock_period_in_ns >> 1);
+
+ /* ...and one less period for the delay time. */
+ ideal_sample_delay_in_ns -= clock_period_in_ns;
+
+ /* Jam a negative ideal sample delay to zero. */
+ if (ideal_sample_delay_in_ns < 0)
+ ideal_sample_delay_in_ns = 0;
+
+ /*
+ * We have a new ideal sample delay, so re-compute the quantized
+ * delay.
+ */
+
+ sample_delay_factor =
+ ns_to_cycles(
+ ideal_sample_delay_in_ns << dll_delay_shift,
+ clock_period_in_ns, 0);
+
+ if (sample_delay_factor > nfc->max_sample_delay_factor)
+ sample_delay_factor = nfc->max_sample_delay_factor;
+
+ }
+
+ /* Control arrives here when we're ready to return our results. */
+
+return_results:
+
+ hw->data_setup_in_cycles = data_setup_in_cycles;
+ hw->data_hold_in_cycles = data_hold_in_cycles;
+ hw->address_setup_in_cycles = address_setup_in_cycles;
+ hw->use_half_periods = dll_use_half_periods;
+ hw->sample_delay_factor = sample_delay_factor;
+
+ /* Return success. */
+
+ return 0;
+
+}