| Message ID | 1398879850-9111-5-git-send-email-dianders@chromium.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Wed, 30 Apr 2014, Doug Anderson wrote: > We're adding i2c tunneling to the list of things that goes over > cros_ec. i2c tunneling can be slooooooow, so increase our deadline to > 100ms to account for that. > > Signed-off-by: Doug Anderson <dianders@chromium.org> > Acked-by: Lee Jones <lee.jones@linaro.org> > Reviewed-by: Simon Glass <sjg@chromium.org> > Tested-by: Andrew Bresticker <abrestic@chromium.org> > Tested-by: Stephen Warren <swarren@nvidia.com> > --- > Changes in v3: None > Changes in v2: None > > drivers/mfd/cros_ec_spi.c | 24 ++++++++++++++++-------- > 1 file changed, 16 insertions(+), 8 deletions(-) Applied, thanks. > diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c > index 4f863c3..0b8d328 100644 > --- a/drivers/mfd/cros_ec_spi.c > +++ b/drivers/mfd/cros_ec_spi.c > @@ -39,14 +39,22 @@ > #define EC_MSG_PREAMBLE_COUNT 32 > > /* > - * We must get a response from the EC in 5ms. This is a very long > - * time, but the flash write command can take 2-3ms. The EC command > - * processing is currently not very fast (about 500us). We could > - * look at speeding this up and making the flash write command a > - * 'slow' command, requiring a GET_STATUS wait loop, like flash > - * erase. > - */ > -#define EC_MSG_DEADLINE_MS 5 > + * Allow for a long time for the EC to respond. We support i2c > + * tunneling and support fairly long messages for the tunnel (249 > + * bytes long at the moment). If we're talking to a 100 kHz device > + * 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. > + * > + * 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 > + * consider having slow commands like this require a GET_STATUS > + * wait loop. The 'flash write' command would be another candidate > + * for this, clocking in at 2-3ms. > + */ > +#define EC_MSG_DEADLINE_MS 100 > > /* > * Time between raising the SPI chip select (for the end of a
diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c index 4f863c3..0b8d328 100644 --- a/drivers/mfd/cros_ec_spi.c +++ b/drivers/mfd/cros_ec_spi.c @@ -39,14 +39,22 @@ #define EC_MSG_PREAMBLE_COUNT 32 /* - * We must get a response from the EC in 5ms. This is a very long - * time, but the flash write command can take 2-3ms. The EC command - * processing is currently not very fast (about 500us). We could - * look at speeding this up and making the flash write command a - * 'slow' command, requiring a GET_STATUS wait loop, like flash - * erase. - */ -#define EC_MSG_DEADLINE_MS 5 + * Allow for a long time for the EC to respond. We support i2c + * tunneling and support fairly long messages for the tunnel (249 + * bytes long at the moment). If we're talking to a 100 kHz device + * 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. + * + * 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 + * consider having slow commands like this require a GET_STATUS + * wait loop. The 'flash write' command would be another candidate + * for this, clocking in at 2-3ms. + */ +#define EC_MSG_DEADLINE_MS 100 /* * Time between raising the SPI chip select (for the end of a