On 13/11/17 21:19, Brian Norris wrote: > + others > > On Mon, Nov 13, 2017 at 09:05:39PM +0000, Jon Hunter wrote: >> On the Tegra124 Nyan-Big chromebook the very first SPI message sent to >> the EC is failing. >> >> The Tegra SPI driver configures the SPI chip-selects to be active-high >> by default (and always has for many years). The EC SPI requires an >> active-low chip-select and so the Tegra chip-select is reconfigured to >> be active-low when the EC SPI driver calls spi_setup(). The problem is >> that if the first SPI message to the EC is sent too soon after >> reconfiguring the SPI chip-select, it fails. >> >> The EC SPI driver prevents back-to-back SPI messages being sent too >> soon by keeping track of the time the last transfer was sent via the >> variable 'last_transfer_ns'. To prevent the very first transfer being >> sent too soon, initialise the 'last_transfer_ns' variable after calling >> spi_setup() and before sending the first SPI message. >> >> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> >> --- >> Looks like this issue has been around for several Linux releases now >> and it just depends on timing if this issue is seen or not and so there >> is no specific commit this fixes. However, would be good to include for >> v4.15. > > I wonder if that doesn't mean we should have a stable tag still? > > Cc: <stable@xxxxxxxxxxxxxxx> I was thinking about that as well after I sent it. I have resent as a V2 CC'ing stable. Cheers Jon -- nvpublic -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
