linux-kernel - [PATCH 1/3] spi: dw: select SS0 when gpio cs is used

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Message-Id: <20221202094859.7869-1-edmund.berenson@emlix.com>
Date:   Fri,  2 Dec 2022 10:48:59 +0100
From:   Edmund Berenson <edmund.berenson@...ix.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Edmund Berenson <edmund.berenson@...ix.com>,
        Lukasz Zemla <Lukasz.Zemla@...dward.com>,
        Serge Semin <fancer.lancer@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] spi: dw: select SS0 when gpio cs is used

SER register contains only 4-bit bit-field for enabling 4 SPI chip selects.
If gpio cs are used the cs number may be >= 4. To ensure we do not write
outside of the valid area, we choose SS0 in case of gpio cs to start
spi transfer.

Co-developed-by: Lukasz Zemla <Lukasz.Zemla@...dward.com>
Signed-off-by: Lukasz Zemla <Lukasz.Zemla@...dward.com>
Signed-off-by: Edmund Berenson <edmund.berenson@...ix.com>
---
 drivers/spi/spi-dw-core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index 99edddf9958b..57c9e384d6d4 100644
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -94,6 +94,10 @@ void dw_spi_set_cs(struct spi_device *spi, bool enable)
 {
 	struct dw_spi *dws = spi_controller_get_devdata(spi->controller);
 	bool cs_high = !!(spi->mode & SPI_CS_HIGH);
+	u8 enable_cs = 0;
+
+	if (!spi->cs_gpiod)
+		enable_cs = spi->chip_select;
 
 	/*
 	 * DW SPI controller demands any native CS being set in order to
@@ -103,7 +107,7 @@ void dw_spi_set_cs(struct spi_device *spi, bool enable)
 	 * support active-high or active-low CS level.
 	 */
 	if (cs_high == enable)
-		dw_writel(dws, DW_SPI_SER, BIT(spi->chip_select));
+		dw_writel(dws, DW_SPI_SER, BIT(enable_cs));
 	else
 		dw_writel(dws, DW_SPI_SER, 0);
 }
-- 
2.37.4