i2c: bcm2835: add I2C_AQ_NO_CLK_STRETCH

As reported in the links given below. the BCM2835 has a hardware bug in
its i2c module which prevents a correct clock stretching. This patch
adds the I2C_AQ_NO_CLK_STRETCH quirk flag to i2c-bcm2835.

Signed-off-by: Nicola Corna <nicola@corna.info>
[wsa: put the links into the code as comments]
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index 3032b89ac60b5212c0e918abdf1d68c6381ff002..818b051d25e6dea491c366b0767aedcfd707b320 100644 (file)
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -222,6 +222,15 @@ static const struct i2c_algorithm bcm2835_i2c_algo = {
        .functionality  = bcm2835_i2c_func,
 };
 
+/*
+ * This HW was reported to have problems with clock stretching:
+ * http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
+ * https://www.raspberrypi.org/forums/viewtopic.php?p=146272
+ */
+static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
+       .flags = I2C_AQ_NO_CLK_STRETCH,
+};
+
 static int bcm2835_i2c_probe(struct platform_device *pdev)
 {
        struct bcm2835_i2c_dev *i2c_dev;
@@ -293,6 +302,7 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
        adap->algo = &bcm2835_i2c_algo;
        adap->dev.parent = &pdev->dev;
        adap->dev.of_node = pdev->dev.of_node;
+       adap->quirks = &bcm2835_i2c_quirks;
 
        bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);