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spi: use specific last_cs instead of last_cs_enable

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Commit d40f0b6f2e instroduced last_cs_enable to avoid setting
chipselect if it's not necessary, but it also introduces a bug. The
chipselect may not be set correctly on multi-device SPI busses. The
reason is that we can't judge the chipselect by bool last_cs_enable,
since chipselect may be modified after other devices were accessed.

So we should record the specific state of chipselect in case of
confusion.

Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
Link: https://lore.kernel.org/r/20220217141234.72737-1-yun.zhou@windriver.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Yun Zhou 2022-02-17 22:12:34 +08:00 committed by Mark Brown
parent fcaaf76ed5
commit 6bb477df04
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GPG key ID: 24D68B725D5487D0
2 changed files with 9 additions and 4 deletions
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8
drivers/spi/spi.c
View file

@ -926,13 +926,14 @@ static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
* Avoid calling into the driver (or doing delays) if the chip select
* isn't actually changing from the last time this was called.
*/
if (!force && (spi->controller->last_cs_enable == enable) &&
if (!force && ((enable && spi->controller->last_cs == spi->chip_select) ||
(!enable && spi->controller->last_cs != spi->chip_select)) &&
(spi->controller->last_cs_mode_high == (spi->mode & SPI_CS_HIGH)))
return;
trace_spi_set_cs(spi, activate);
spi->controller->last_cs_enable = enable;
spi->controller->last_cs = enable ? spi->chip_select : -1;
spi->controller->last_cs_mode_high = spi->mode & SPI_CS_HIGH;
if ((spi->cs_gpiod || !spi->controller->set_cs_timing) && !activate) {
@ -3016,6 +3017,9 @@ int spi_register_controller(struct spi_controller *ctlr)
goto free_bus_id;
}
/* setting last_cs to -1 means no chip selected */
ctlr->last_cs = -1;
status = device_add(&ctlr->dev);
if (status < 0)
goto free_bus_id;

5
include/linux/spi/spi.h
View file

@ -370,7 +370,8 @@ extern struct spi_device *spi_new_ancillary_device(struct spi_device *spi, u8 ch
* @cur_msg_prepared: spi_prepare_message was called for the currently
* in-flight message
* @cur_msg_mapped: message has been mapped for DMA
* @last_cs_enable: was enable true on the last call to set_cs.
* @last_cs: the last chip_select that is recorded by set_cs, -1 on non chip
* selected
* @last_cs_mode_high: was (mode & SPI_CS_HIGH) true on the last call to set_cs.
* @xfer_completion: used by core transfer_one_message()
* @busy: message pump is busy
@ -603,7 +604,7 @@ struct spi_controller {
bool auto_runtime_pm;
bool cur_msg_prepared;
bool cur_msg_mapped;
bool last_cs_enable;
char last_cs;
bool last_cs_mode_high;
bool fallback;
struct completion xfer_completion;