linux-kernel - [PATCH AUTOSEL 5.4 004/187] spi: cadence: Correct handling of native chipselect

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Date:   Fri, 27 Dec 2019 12:37:52 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-spi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 004/187] spi: cadence: Correct handling of native chipselect

From: Charles Keepax <ckeepax@...nsource.cirrus.com>

[ Upstream commit 61acd19f9c56fa0809285346bd0bd4a926ab0da0 ]

To fix a regression on the Cadence SPI driver, this patch reverts
commit 6046f5407ff0 ("spi: cadence: Fix default polarity of native
chipselect").

This patch was not the correct fix for the issue. The SPI framework
calls the set_cs line with the logic level it desires on the chip select
line, as such the old is_high handling was correct. However, this was
broken by the fact that before commit 3e5ec1db8bfe ("spi: Fix SPI_CS_HIGH
setting when using native and GPIO CS") all controllers that offered
the use of a GPIO chip select had SPI_CS_HIGH applied, even for hardware
chip selects. This caused the value passed into the driver to be inverted.
Which unfortunately makes it look like a logical enable the chip select
value.

Since the core was corrected to not unconditionally apply SPI_CS_HIGH,
the Cadence driver, whilst using the hardware chip select, will deselect
the chip select every time we attempt to communicate with the device,
which results in failed communications.

Fixes: 3e5ec1db8bfe ("spi: Fix SPI_CS_HIGH setting when using native and GPIO CS")
Signed-off-by: Charles Keepax <ckeepax@...nsource.cirrus.com>
Acked-by: Linus Walleij <linus.walleij@...aro.org>
Link: https://lore.kernel.org/r/20191126164140.6240-1-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/spi/spi-cadence.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-cadence.c b/drivers/spi/spi-cadence.c
index c36587b42e95..82a0ee09cbe1 100644
--- a/drivers/spi/spi-cadence.c
+++ b/drivers/spi/spi-cadence.c
@@ -168,16 +168,16 @@ static void cdns_spi_init_hw(struct cdns_spi *xspi)
 /**
  * cdns_spi_chipselect - Select or deselect the chip select line
  * @spi:	Pointer to the spi_device structure
- * @enable:	Select (1) or deselect (0) the chip select line
+ * @is_high:	Select(0) or deselect (1) the chip select line
  */
-static void cdns_spi_chipselect(struct spi_device *spi, bool enable)
+static void cdns_spi_chipselect(struct spi_device *spi, bool is_high)
 {
 	struct cdns_spi *xspi = spi_master_get_devdata(spi->master);
 	u32 ctrl_reg;

 	ctrl_reg = cdns_spi_read(xspi, CDNS_SPI_CR);

-	if (!enable) {
+	if (is_high) {
 		/* Deselect the slave */
 		ctrl_reg |= CDNS_SPI_CR_SSCTRL;
 	} else {
-- 
2.20.1