tree 50430d2064424fd9ce286995dafaae840110f54f
parent 6ff33f3902c3b1c5d0db6b1e2c70b6d76fba357f
author Vignesh R <vigneshr@ti.com> 1444636322 +0530
committer Mark Brown <broonie@kernel.org> 1444669128 +0100

spi: ti-qspi: Fix data corruption seen on r/w stress test

Writing invalid command to QSPI_SPI_CMD_REG will terminate current
transfer and de-assert the chip select. This has to be done before
calling spi_finalize_current_message(). Because
spi_finalize_current_message() will mark the end of current message
transfer and schedule the next transfer. If the chipselect is not
de-asserted before calling spi_finalize_current_message() then the next
transfer will overlap with the previous transfer leading to data
corruption.
__spi_pump_message() can be called either from kthread worker context or
directly from the calling process's context. It is possible that these
two calls can race against each other. But race is serialized by
checking whether master->cur_msg == NULL (pointer to msg being handled
by transfer_one() at present). The master->cur_msg is set to NULL when
spi_finalize_current_message() is called on that message, which means
calling spi_finalize_current_message() allows __spi_sync() to pump next
message in calling process context.
Now if spi-ti-qspi calls spi_finalize_current_message() before we
terminate transfer at hardware side, if __spi_pump_message() is called
from process context then the successive transactions can overlap.

Fix this by moving writing invalid command to QSPI_SPI_CMD_REG to
before calling spi_finalize_current_message() call.

Cc: stable@vger.kernel.org # v3.12+
Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>