From: Douglas Anderson <diand...@chromium.org> Date: Fri, May 10, 2019 at 3:35 PM To: Mark Brown, Benson Leung, Enric Balletbo i Serra Cc: <linux-rockc...@lists.infradead.org>, <drink...@chromium.org>, Guenter Roeck, <briannor...@chromium.org>, <m...@chromium.org>, Douglas Anderson, <linux-kernel@vger.kernel.org>
> All currently known ECs in the wild are very sensitive to timing. > Specifically the ECs are known to drop a transfer if more than 8 ms > passes from the assertion of the chip select until the transfer > finishes. > > Let's use the new feature introduced in the patch ("spi: Allow SPI > devices to specify that they are timing sensitive") to specify this > and increase the success rate of our transfers. > > NOTE: if future Chrome OS ECs ever fix themselves to be less sensitive > then we could consider adding a property (or compatible string) to not > set this property. For now we need it across the board. > > With this change we can revert the commit 37a186225a0c > ("platform/chrome: cros_ec_spi: Transfer messages at high priority"). > ...and, in fact, transfers are _even more_ reliable than they were > with that commit since the SPI framework will use a higher priority > (realtime) and we no longer lose our priority when we get shunted over > to the message pumping thread (because we now always get shunted and > the thread is high priority). > > Signed-off-by: Douglas Anderson <diand...@chromium.org> Reviewed-by: Guenter Roeck <gro...@chromium.org> > --- > > drivers/platform/chrome/cros_ec_spi.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/platform/chrome/cros_ec_spi.c > b/drivers/platform/chrome/cros_ec_spi.c > index 8e9451720e73..757a115502ec 100644 > --- a/drivers/platform/chrome/cros_ec_spi.c > +++ b/drivers/platform/chrome/cros_ec_spi.c > @@ -703,6 +703,7 @@ static int cros_ec_spi_probe(struct spi_device *spi) > > spi->bits_per_word = 8; > spi->mode = SPI_MODE_0; > + spi->timing_sensitive = true; > err = spi_setup(spi); > if (err < 0) > return err; > -- > 2.21.0.1020.gf2820cf01a-goog >