i2c: bcm2835: Make clock-stretch timeout configurable

The default clock-stretch timeout is 35 mS, which works well for
SMBus, but there are some I2C devices which can stretch the clock even
longer. Rather than trying to prescribe a safe default for everyone,
allow the timeout to be configured.

Signed-off-by: Alex Crawford <raspberrypi/linux@code.acrawford.com>

diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index f98033c..340f294 100644 (file)
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -60,6 +60,10 @@ static unsigned int debug;
 module_param(debug, uint, 0644);
 MODULE_PARM_DESC(debug, "1=err, 2=isr, 3=xfer");
 
+static unsigned int clk_tout_ms = 35; /* SMBUs-recommended 35ms */
+module_param(clk_tout_ms, uint, 0644);
+MODULE_PARM_DESC(clk_tout_ms, "clock-stretch timeout (mS)");
+
 #define BCM2835_DEBUG_MAX      512
 struct bcm2835_debug {
        struct i2c_msg *msg;
@@ -219,12 +223,12 @@ static int clk_bcm2835_i2c_set_rate(struct clk_hw *hw, unsigned long rate,
                           (redl << BCM2835_I2C_REDL_SHIFT));
 
        /*
-        * Set the clock stretch timeout to the SMBUs-recommended 35ms.
+        * Set the clock stretch timeout.
         */
-       if (rate > 0xffff*1000/35)
+       if (rate > 0xffff*1000/clk_tout_ms)
            clk_tout = 0xffff;
        else
-           clk_tout = 35*rate/1000;
+           clk_tout = clk_tout_ms*rate/1000;
 
        bcm2835_i2c_writel(div->i2c_dev, BCM2835_I2C_CLKT, clk_tout);