Unverified Commit 6bb477df authored by Yun Zhou's avatar Yun Zhou Committed by Mark Brown
Browse files

spi: use specific last_cs instead of last_cs_enable 



Commit d40f0b6f 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: default avatarYun Zhou <yun.zhou@windriver.com>
Link: https://lore.kernel.org/r/20220217141234.72737-1-yun.zhou@windriver.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent fcaaf76e

drivers/spi/spi.c

+6 −2
Original line number Diff line number Diff line
@@ -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;

include/linux/spi/spi.h

+3 −2
Original line number Diff line number Diff line
@@ -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;