From ca691f7118087a652e4d6c83a30f5ed6d5acbf14 Mon Sep 17 00:00:00 2001 From: Doug Anderson Date: Wed, 1 Mar 2017 12:58:32 +0100 Subject: mfd: cros ec: spi: Increase wait time to 200ms This is a sucky change to bump up the time we'll wait for the EC. Why is it sucky? If 200ms for a transfer is a common thing it will have a massively bad impact on keyboard responsiveness. It still seems like a good idea to do this, though, because we have a gas gauge that claims that in an extreme case it could stretch the i2c clock for 144ms. It's not a common case so it shouldn't affect responsiveness, but it can happen. It's much better to have a single slow keyboard response than to start returning errors when we don't have to. In newer EC designs we should probably implement a virtual battery to respond to the kernel to insulate the kernel from these types of issues. Signed-off-by: Doug Anderson Signed-off-by: Enric Balletbo i Serra Signed-off-by: Lee Jones --- drivers/mfd/cros_ec_spi.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'drivers') diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c index a518832ed5f5..c9714072e224 100644 --- a/drivers/mfd/cros_ec_spi.c +++ b/drivers/mfd/cros_ec_spi.c @@ -45,8 +45,11 @@ * on the other end and need to transfer ~256 bytes, then we need: * 10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms * - * We'll wait 4 times that to handle clock stretching and other - * paranoia. + * We'll wait 8 times that to handle clock stretching and other + * paranoia. Note that some battery gas gauge ICs claim to have a + * clock stretch of 144ms in rare situations. That's incentive for + * not directly passing i2c through, but it's too late for that for + * existing hardware. * * It's pretty unlikely that we'll really see a 249 byte tunnel in * anything other than testing. If this was more common we might @@ -54,7 +57,7 @@ * wait loop. The 'flash write' command would be another candidate * for this, clocking in at 2-3ms. */ -#define EC_MSG_DEADLINE_MS 100 +#define EC_MSG_DEADLINE_MS 200 /* * Time between raising the SPI chip select (for the end of a -- cgit v1.2.3