Hi Jon, On Tue, Nov 14, 2017 at 02:43:27PM +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. > > Cc: <stable@xxxxxxxxxxxxxxx> > > Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx> > Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx> Acked-by: Benson Leung <bleung@xxxxxxxxxxxx> -- Benson Leung Staff Software Engineer Chrome OS Kernel Google Inc. bleung@xxxxxxxxxx Chromium OS Project bleung@xxxxxxxxxxxx
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