[PATCH 3/8] spi: dw: Add support for Pensando Elba SoC SPI

[Brad Larson]

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 at pensando.io>
---
 drivers/spi/spi-dw-mmio.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index 17c06039a74d..417bd2125c07 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 +237,38 @@ 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) {
+		if (spi->cs_gpiod) {
+			/*
+			 * 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, so use CS0.
+			 */
+			dw_writel(dws, DW_SPI_SER, BIT(0));
+		} else {
+			/*
+			 * Using the intrinsic DW chip-select; set the
+			 * appropriate CS.
+			 */
+			dw_writel(dws, DW_SPI_SER, BIT(spi->chip_select));
+		}
+	} 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 +383,7 @@ 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