Commit 7b618638 authored Jun 16, 2015 by Silvan Wicki Committed by Wolfram Sang Jun 17, 2015

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 <linux_wi@tinag.ch>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

parent b6eba559

drivers/i2c/busses/i2c-bcm2835.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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);

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