Commit 9495b9b3 authored by Eric Anholt's avatar Eric Anholt Committed by Wolfram Sang
Browse files

i2c: bcm2835: Avoid clock stretching timeouts 



The CLKT register contains at poweron 0x40, which at our typical 100kHz
bus rate means .64ms. But there is no specified limit to how long devices
should be able to stretch the clocks, so just disable the timeout. We
still have a timeout wrapping the entire transfer.

Signed-off-by: default avatarEric Anholt <eric@anholt.net>
Signed-off-by: default avatarStefan Wahren <stefan.wahren@i2se.com>
BugLink: https://github.com/raspberrypi/linux/issues/3064


Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent e783362e

drivers/i2c/busses/i2c-bcm2835.c

+11 −0
Original line number Diff line number Diff line
@@ -23,6 +23,11 @@ 
#define BCM2835_I2C_FIFO	0x10

#define BCM2835_I2C_DIV		0x14

#define BCM2835_I2C_DEL		0x18

/*

 * 16-bit field for the number of SCL cycles to wait after rising SCL

 * before deciding the slave is not responding. 0 disables the

 * timeout detection.

 */

#define BCM2835_I2C_CLKT	0x1c



#define BCM2835_I2C_C_READ	BIT(0)
@@ -474,6 +479,12 @@ static int bcm2835_i2c_probe(struct platform_device *pdev) 
	adap->dev.of_node = pdev->dev.of_node;

	adap->quirks = of_device_get_match_data(&pdev->dev);



	/*

	 * Disable the hardware clock stretching timeout. SMBUS

	 * specifies a limit for how long the device can stretch the

	 * clock, but core I2C doesn't.

	 */

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_CLKT, 0);

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);



	ret = i2c_add_adapter(adap);