linux-kernel - [PATCH v2 03/13] spi: dw: Add support for Pensando Elba SoC SPI

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Date:   Sun, 28 Mar 2021 18:59:28 -0700
From:   Brad Larson <brad@...sando.io>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     arnd@...db.de, linus.walleij@...aro.org, bgolaszewski@...libre.com,
        broonie@...nel.org, fancer.lancer@...il.com,
        adrian.hunter@...el.com, ulf.hansson@...aro.org, olof@...om.net,
        brad@...sando.io, linux-gpio@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 03/13] spi: dw: Add support for Pensando Elba SoC SPI

The Pensando Elba SoC uses a GPIO based chip select
for two DW SPI busses with each bus having two
chip selects.

Signed-off-by: Brad Larson <brad@...sando.io>
---
 drivers/spi/spi-dw-mmio.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index 17c06039a74d..c323a5ceecb8 100644
--- a/drivers/spi/spi-dw-mmio.c
+++ b/drivers/spi/spi-dw-mmio.c
@@ -56,7 +56,7 @@ struct dw_spi_mscc {
 /*
  * The Designware SPI controller (referred to as master in the documentation)
  * automatically deasserts chip select when the tx fifo is empty. The chip
- * selects then needs to be either driven as GPIOs or, for the first 4 using the
+ * selects then needs to be either driven as GPIOs or, for the first 4 using
  * the SPI boot controller registers. the final chip select is an OR gate
  * between the Designware SPI controller and the SPI boot controller.
  */
@@ -237,6 +237,31 @@ static int dw_spi_canaan_k210_init(struct platform_device *pdev,
 	return 0;
 }
 
+static void dw_spi_elba_set_cs(struct spi_device *spi, bool enable)
+{
+	struct dw_spi *dws = spi_master_get_devdata(spi->master);
+
+	if (!enable) {
+		/*
+		 * Using a GPIO-based chip-select, the DW SPI
+		 * controller still needs its own CS bit selected
+		 * to start the serial engine.  On Elba the specific
+		 * CS doesn't matter to start the serial engine,
+		 * so using CS0.
+		 */
+		dw_writel(dws, DW_SPI_SER, BIT(0));
+	} else {
+		dw_writel(dws, DW_SPI_SER, 0);
+	}
+}
+
+static int dw_spi_elba_init(struct platform_device *pdev,
+			    struct dw_spi_mmio *dwsmmio)
+{
+	dwsmmio->dws.set_cs = dw_spi_elba_set_cs;
+	return 0;
+}
+
 static int dw_spi_mmio_probe(struct platform_device *pdev)
 {
 	int (*init_func)(struct platform_device *pdev,
@@ -351,6 +376,7 @@ static const struct of_device_id dw_spi_mmio_of_match[] = {
 	{ .compatible = "intel,keembay-ssi", .data = dw_spi_keembay_init},
 	{ .compatible = "microchip,sparx5-spi", dw_spi_mscc_sparx5_init},
 	{ .compatible = "canaan,k210-spi", dw_spi_canaan_k210_init},
+	{ .compatible = "pensando,elba-spi", .data = dw_spi_elba_init},
 	{ /* end of table */}
 };
 MODULE_DEVICE_TABLE(of, dw_spi_mmio_of_match);
-- 
2.17.1