From 4dbfb5f4401f845903679afbfeb4b97b47bb2331 Mon Sep 17 00:00:00 2001 From: Nicola Corna Date: Thu, 29 Oct 2015 12:34:25 +0100 Subject: [PATCH] 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 [wsa: put the links into the code as comments] Signed-off-by: Wolfram Sang --- drivers/i2c/busses/i2c-bcm2835.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c index 3032b89ac60b..818b051d25e6 100644 --- 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);