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>
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@ -50,6 +50,8 @@
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#define BCM2835_I2C_S_CLKT BIT(9)
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#define BCM2835_I2C_S_LEN BIT(10) /* Fake bit for SW error reporting */
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#define BCM2835_I2C_BITMSK_S 0x03FF
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#define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))
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struct bcm2835_i2c_dev {
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@ -111,6 +113,7 @@ static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
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u32 val, err;
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val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
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val &= BCM2835_I2C_BITMSK_S;
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bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);
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err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
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