diff options
| author | Doug Anderson <dianders@chromium.org> | 2017-03-01 12:58:32 +0100 |
|---|---|---|
| committer | Lee Jones <lee.jones@linaro.org> | 2017-04-27 09:25:04 +0100 |
| commit | ca691f7118087a652e4d6c83a30f5ed6d5acbf14 (patch) | |
| tree | 59599bc8510486259975f08336f0737eecae5e83 /drivers/mfd | |
| parent | d5aa11bfe9cebb4a3912b11748fd84aa15454229 (diff) | |
| download | linux-ca691f7118087a652e4d6c83a30f5ed6d5acbf14.tar.bz2 | |
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 <dianders@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Diffstat (limited to 'drivers/mfd')
| -rw-r--r-- | drivers/mfd/cros_ec_spi.c | 9 |
1 files changed, 6 insertions, 3 deletions
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 |