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Commit d20e4ed6 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab
Browse files

[media] em28xx: use a better value for I2C timeouts 

In the lack of a better spec, let's assume the timeout
values compatible with SMBus spec:
	http://smbus.org/specs/smbus110.pdf



at chapter 8 - Electrical Characteristics of SMBus devices

Ok, SMBus is a subset of I2C, and not all devices will be
following it, but the timeout value before this patch was not
even following the spec.

So, while we don't have a better guess for it, use 35 + 1
ms as the timeout.

Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent d1b7213b

drivers/media/usb/em28xx/em28xx.h

+15 −2
Original line number Diff line number Diff line
@@ -183,8 +183,21 @@ 


#define EM28XX_INTERLACED_DEFAULT 1



/* time in msecs to wait for i2c writes to finish */

#define EM2800_I2C_XFER_TIMEOUT		20

/*

 * Time in msecs to wait for i2c xfers to finish.

 * 35ms is the maximum time a SMBUS device could wait when

 * clock stretching is used. As the transfer itself will take

 * some time to happen, set it to 35 ms.

 *

 * Ok, I2C doesn't specify any limit. So, eventually, we may need

 * to increase this timeout.

 *

 * FIXME: this assumes that an I2C message is not longer than 1ms.

 * This is actually dependent on the I2C bus speed, although most

 * devices use a 100kHz clock. So, this assumtion is true most of

 * the time.

 */

#define EM28XX_I2C_XFER_TIMEOUT		36



/* time in msecs to wait for AC97 xfers to finish */

#define EM28XX_AC97_XFER_TIMEOUT	100