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path: root/drivers/tty/serial/msm_serial.c
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Diffstat (limited to 'drivers/tty/serial/msm_serial.c')
-rw-r--r--drivers/tty/serial/msm_serial.c101
1 files changed, 66 insertions, 35 deletions
diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index 96d3ce8dc2dc..b7d80bd57db9 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -861,37 +861,72 @@ struct msm_baud_map {
};
static const struct msm_baud_map *
-msm_find_best_baud(struct uart_port *port, unsigned int baud)
+msm_find_best_baud(struct uart_port *port, unsigned int baud,
+ unsigned long *rate)
{
- unsigned int i, divisor;
- const struct msm_baud_map *entry;
+ struct msm_port *msm_port = UART_TO_MSM(port);
+ unsigned int divisor, result;
+ unsigned long target, old, best_rate = 0, diff, best_diff = ULONG_MAX;
+ const struct msm_baud_map *entry, *end, *best;
static const struct msm_baud_map table[] = {
- { 1536, 0x00, 1 },
- { 768, 0x11, 1 },
- { 384, 0x22, 1 },
- { 192, 0x33, 1 },
- { 96, 0x44, 1 },
- { 48, 0x55, 1 },
- { 32, 0x66, 1 },
- { 24, 0x77, 1 },
- { 16, 0x88, 1 },
- { 12, 0x99, 6 },
- { 8, 0xaa, 6 },
- { 6, 0xbb, 6 },
- { 4, 0xcc, 6 },
- { 3, 0xdd, 8 },
- { 2, 0xee, 16 },
{ 1, 0xff, 31 },
- { 0, 0xff, 31 },
+ { 2, 0xee, 16 },
+ { 3, 0xdd, 8 },
+ { 4, 0xcc, 6 },
+ { 6, 0xbb, 6 },
+ { 8, 0xaa, 6 },
+ { 12, 0x99, 6 },
+ { 16, 0x88, 1 },
+ { 24, 0x77, 1 },
+ { 32, 0x66, 1 },
+ { 48, 0x55, 1 },
+ { 96, 0x44, 1 },
+ { 192, 0x33, 1 },
+ { 384, 0x22, 1 },
+ { 768, 0x11, 1 },
+ { 1536, 0x00, 1 },
};
- divisor = uart_get_divisor(port, baud);
+ best = table; /* Default to smallest divider */
+ target = clk_round_rate(msm_port->clk, 16 * baud);
+ divisor = DIV_ROUND_CLOSEST(target, 16 * baud);
+
+ end = table + ARRAY_SIZE(table);
+ entry = table;
+ while (entry < end) {
+ if (entry->divisor <= divisor) {
+ result = target / entry->divisor / 16;
+ diff = abs(result - baud);
+
+ /* Keep track of best entry */
+ if (diff < best_diff) {
+ best_diff = diff;
+ best = entry;
+ best_rate = target;
+ }
- for (i = 0, entry = table; i < ARRAY_SIZE(table); i++, entry++)
- if (entry->divisor <= divisor)
- break;
+ if (result == baud)
+ break;
+ } else if (entry->divisor > divisor) {
+ old = target;
+ target = clk_round_rate(msm_port->clk, old + 1);
+ /*
+ * The rate didn't get any faster so we can't do
+ * better at dividing it down
+ */
+ if (target == old)
+ break;
- return entry; /* Default to smallest divider */
+ /* Start the divisor search over at this new rate */
+ entry = table;
+ divisor = DIV_ROUND_CLOSEST(target, 16 * baud);
+ continue;
+ }
+ entry++;
+ }
+
+ *rate = best_rate;
+ return best;
}
static int msm_set_baud_rate(struct uart_port *port, unsigned int baud,
@@ -900,22 +935,20 @@ static int msm_set_baud_rate(struct uart_port *port, unsigned int baud,
unsigned int rxstale, watermark, mask;
struct msm_port *msm_port = UART_TO_MSM(port);
const struct msm_baud_map *entry;
- unsigned long flags;
-
- entry = msm_find_best_baud(port, baud);
-
- msm_write(port, entry->code, UART_CSR);
-
- if (baud > 460800)
- port->uartclk = baud * 16;
+ unsigned long flags, rate;
flags = *saved_flags;
spin_unlock_irqrestore(&port->lock, flags);
- clk_set_rate(msm_port->clk, port->uartclk);
+ entry = msm_find_best_baud(port, baud, &rate);
+ clk_set_rate(msm_port->clk, rate);
+ baud = rate / 16 / entry->divisor;
spin_lock_irqsave(&port->lock, flags);
*saved_flags = flags;
+ port->uartclk = rate;
+
+ msm_write(port, entry->code, UART_CSR);
/* RX stale watermark */
rxstale = entry->rxstale;
@@ -1577,8 +1610,6 @@ static int msm_serial_probe(struct platform_device *pdev)
msm_port->pclk = devm_clk_get(&pdev->dev, "iface");
if (IS_ERR(msm_port->pclk))
return PTR_ERR(msm_port->pclk);
-
- clk_set_rate(msm_port->clk, 1843200);
}
port->uartclk = clk_get_rate(msm_port->clk);