From: Silvan Wicki Date: Tue, 16 Jun 2015 15:40:59 +0000 (+0200) Subject: i2c: bcm2835: clear reserved bits in S-Register X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=7b618638a518ce7083fcca1bc7181a5c6337277a;p=linux-beck.git i2c: bcm2835: clear reserved bits in S-Register The datasheet mentions on page 31 that the bits 10-31 must be read as don't care and written as 0. https://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf We cannot guarantee that we read bits 10-31 as always 0 (because the datasheet says read as don't care). We clear the bits with a bitmask to prevent writing back unknown data at the reserved bits. Signed-off-by: Silvan Wicki Acked-by: Stephen Warren Signed-off-by: Wolfram Sang --- diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c index c9336a3202d5..aa06da17e30e 100644 --- a/drivers/i2c/busses/i2c-bcm2835.c +++ b/drivers/i2c/busses/i2c-bcm2835.c @@ -50,6 +50,8 @@ #define BCM2835_I2C_S_CLKT BIT(9) #define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */ +#define BCM2835_I2C_BITMSK_S 0x03FF + #define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000)) struct bcm2835_i2c_dev { @@ -111,6 +113,7 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data) u32 val, err; val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S); + val &= BCM2835_I2C_BITMSK_S; bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val); err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);