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stm32: spi: read spi->dr into a dummy variable

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(cherry-pick back to ToT)

In setup_for_transaction(), read spi->dr into a dummy variable instead
of into in_msg[0]. Since in_msg[0] is an alias for a command's port number,
this will prevent a command's port number from being over-written if spi
transaction is terminated early while a command is still in progress.

BUG=chrome-os-partner:28979
BRANCH=nyan
TEST=passed factory_test.reboot2 test for >1000 cycles

Signed-off-by: Yen Lin <yelin@nvidia.com>
Reviewed-on: https://chromium-review.googlesource.com/204355
Reviewed-by: Yung-chieh Lo <yjlou@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>

(cherry picked from commit 2b043665850f7c74cd6a4a7f24d7a18b01b378ac)

Change-Id: Ia412fadcd7621f45bbb096771615ce75fe445592
Oiginal-Change-Id: I308ea954d6242fce5b3a70a14660767ac88d8242
Reviewed-on: https://chromium-review.googlesource.com/206920
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Queue: Yung-chieh Lo <yjlou@chromium.org>
Tested-by: Yung-chieh Lo <yjlou@chromium.org>
This commit is contained in:
Yen Lin
2014-06-16 10:43:36 -07:00
committed by chrome-internal-fetch
parent b1dec633cb
commit a02cb09bb7
1 changed files with 2 additions and 1 deletions
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3
chip/stm32/spi.c
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@@ -234,6 +234,7 @@ static void reply(stm32_dma_chan_t *txdma,
static void setup_for_transaction(void)
{
stm32_spi_regs_t *spi = STM32_SPI1_REGS;
volatile uint8_t dummy __attribute__((unused));
/* Not ready to receive yet */
spi->dr = EC_SPI_NOT_READY;
@@ -248,7 +249,7 @@ static void setup_for_transaction(void)
* Read a byte in case there is one pending; this prevents the receive
* DMA from getting that byte right when we start it
*/
*in_msg = spi->dr;
dummy = spi->dr;
/* Start DMA */
dma_start_rx(&dma_rx_option, sizeof(in_msg), in_msg);