From f3083d921d8964b66502a0456f62a9d29cd029ef Mon Sep 17 00:00:00 2001 From: manjugk manjugk Date: Tue, 11 May 2010 11:35:20 -0700 Subject: OMAP2/3: I2C: Errata ID i207: Clear wrong RDR interrupt Under certain rare conditions, I2C_STAT[13].RDR bit may be set and the corresponding interrupt fire, even there is no data in the receive FIFO, or the I2C data transfer is still ongoing. These spurious RDR events must be ignored by the software. This patch handles and ignores RDR spurious interrupts. The below sequence is required in interrupt handler for handling this errata: 1. If RDR is set to 1, clear RDR 2. Read I2C status register and check for BusBusy bit. If BusBusy bit is set, skip remaining steps. 3. If BusBusy bit is not set, perform read operation on I2C status register. 4. If RDR is set, clear the same. Check RDR again and clear if it sets RDR bit again. 5. Perform I2C Data Read operation N number of times(where N is value read from the register BUFSTAT-RXSTAT bit fields). Note: This errata is not applicable for omap2420 and omap4. It is applicable for: 1. omap2430 2. omap34xx(including omap3630). Signed-off-by: Manjunatha GK Cc: Hema Kalliguddi Cc: Nishanth Menon Cc: Aaro Koskinen Signed-off-by: Tony Lindgren Signed-off-by: Ben Dooks --- drivers/i2c/busses/i2c-omap.c | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) (limited to 'drivers/i2c') diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c index 00fd02ec1b65..fdba13137daf 100644 --- a/drivers/i2c/busses/i2c-omap.c +++ b/drivers/i2c/busses/i2c-omap.c @@ -166,6 +166,8 @@ enum { #define SYSC_IDLEMODE_SMART 0x2 #define SYSC_CLOCKACTIVITY_FCLK 0x2 +/* Errata definitions */ +#define I2C_OMAP_ERRATA_I207 (1 << 0) struct omap_i2c_dev { struct device *dev; @@ -199,6 +201,7 @@ struct omap_i2c_dev { u16 bufstate; u16 syscstate; u16 westate; + u16 errata; }; const static u8 reg_map[] = { @@ -498,6 +501,11 @@ static int omap_i2c_init(struct omap_i2c_dev *dev) /* Take the I2C module out of reset: */ omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN); + dev->errata = 0; + + if (cpu_is_omap2430() || cpu_is_omap34xx()) + dev->errata |= I2C_OMAP_ERRATA_I207; + /* Enable interrupts */ dev->iestate = (OMAP_I2C_IE_XRDY | OMAP_I2C_IE_RRDY | OMAP_I2C_IE_ARDY | OMAP_I2C_IE_NACK | @@ -695,6 +703,34 @@ omap_i2c_ack_stat(struct omap_i2c_dev *dev, u16 stat) omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, stat); } +static inline void i2c_omap_errata_i207(struct omap_i2c_dev *dev, u16 stat) +{ + /* + * I2C Errata(Errata Nos. OMAP2: 1.67, OMAP3: 1.8) + * Not applicable for OMAP4. + * Under certain rare conditions, RDR could be set again + * when the bus is busy, then ignore the interrupt and + * clear the interrupt. + */ + if (stat & OMAP_I2C_STAT_RDR) { + /* Step 1: If RDR is set, clear it */ + omap_i2c_ack_stat(dev, OMAP_I2C_STAT_RDR); + + /* Step 2: */ + if (!(omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG) + & OMAP_I2C_STAT_BB)) { + + /* Step 3: */ + if (omap_i2c_read_reg(dev, OMAP_I2C_STAT_REG) + & OMAP_I2C_STAT_RDR) { + omap_i2c_ack_stat(dev, OMAP_I2C_STAT_RDR); + dev_dbg(dev->dev, "RDR when bus is busy.\n"); + } + + } + } +} + /* rev1 devices are apparently only on some 15xx */ #ifdef CONFIG_ARCH_OMAP15XX @@ -834,6 +870,10 @@ complete: } if (stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) { u8 num_bytes = 1; + + if (dev->errata & I2C_OMAP_ERRATA_I207) + i2c_omap_errata_i207(dev, stat); + if (dev->fifo_size) { if (stat & OMAP_I2C_STAT_RRDY) num_bytes = dev->fifo_size; -- cgit v1.2.3