[PATCH 10/11] spi: dw: Add support for Pensando Elba SoC

[Brad Larson <brad@pensando.io>]

The Pensando Elba SoC includes a DW apb_ssi v4 controller
with device specific chip-select control.  The Elba SoC
provides four chip-selects where the native DW IP supports
two chip-selects.  The Elba DW_SPI instance has two native
CS signals that are always overridden.

Signed-off-by: Brad Larson <brad@pensando.io>
---
Change from V3:
- Use more descriptive dt property pensando,syscon-spics
- Minor changes from review input

 drivers/spi/spi-dw-mmio.c | 85 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index 5101c4c6017b..f4636b271818 100644
--- a/drivers/spi/spi-dw-mmio.c
+++ b/drivers/spi/spi-dw-mmio.c
@@ -53,6 +53,24 @@ struct dw_spi_mscc {
 	void __iomem        *spi_mst; /* Not sparx5 */
 };
 
+struct dw_spi_elba {
+	struct regmap *regmap;
+	unsigned int reg;
+};
+
+/*
+ * Elba SoC does not use ssi, pin override is used for cs 0,1 and
+ * gpios for cs 2,3 as defined in the device tree.
+ *
+ * cs:  |       1               0
+ * bit: |---3-------2-------1-------0
+ *      |  cs1   cs1_ovr   cs0   cs0_ovr
+ */
+#define ELBA_SPICS_SHIFT(cs)		(2 * (cs))
+#define ELBA_SPICS_MASK(cs)		(0x3 << ELBA_SPICS_SHIFT(cs))
+#define ELBA_SPICS_SET(cs, val)	\
+			((((val) << 1) | 0x1) << ELBA_SPICS_SHIFT(cs))
+
 /*
  * The Designware SPI controller (referred to as master in the documentation)
  * automatically deasserts chip select when the tx fifo is empty. The chip
@@ -238,6 +256,72 @@ static int dw_spi_canaan_k210_init(struct platform_device *pdev,
 	return 0;
 }
 
+static void elba_spics_set_cs(struct dw_spi_elba *dwselba, int cs, int enable)
+{
+	regmap_update_bits(dwselba->regmap, dwselba->reg, ELBA_SPICS_MASK(cs),
+			   ELBA_SPICS_SET(cs, enable));
+}
+
+static void dw_spi_elba_set_cs(struct spi_device *spi, bool enable)
+{
+	struct dw_spi *dws = spi_master_get_devdata(spi->master);
+	struct dw_spi_mmio *dwsmmio = container_of(dws, struct dw_spi_mmio, dws);
+	struct dw_spi_elba *dwselba = dwsmmio->priv;
+	u8 cs;
+
+	cs = spi->chip_select;
+	if (cs < 2) {
+		/* overridden native chip-select */
+		elba_spics_set_cs(dwselba, spi->chip_select, enable);
+	}
+
+	/*
+	 * The DW SPI controller needs a native CS bit selected to start
+	 * the serial engine and the platform may have fewer native CSs
+	 * than needed, so use CS0 always.
+	 */
+	spi->chip_select = 0;
+	dw_spi_set_cs(spi, enable);
+	spi->chip_select = cs;
+}
+
+static int dw_spi_elba_init(struct platform_device *pdev,
+			    struct dw_spi_mmio *dwsmmio)
+{
+	struct of_phandle_args args;
+	struct dw_spi_elba *dwselba;
+	struct regmap *regmap;
+	int rc;
+
+	rc = of_parse_phandle_with_fixed_args(pdev->dev.of_node,
+			"pensando,syscon-spics", 1, 0, &args);
+	if (rc) {
+		dev_err(&pdev->dev, "could not find spics\n");
+		return rc;
+	}
+
+	regmap = syscon_node_to_regmap(args.np);
+	if (IS_ERR(regmap))
+		return dev_err_probe(&pdev->dev, PTR_ERR(regmap),
+				     "could not map spics");
+
+	dwselba = devm_kzalloc(&pdev->dev, sizeof(*dwselba), GFP_KERNEL);
+	if (!dwselba)
+		return -ENOMEM;
+
+	dwselba->regmap = regmap;
+	dwselba->reg = args.args[0];
+
+	/* deassert cs */
+	elba_spics_set_cs(dwselba, 0, 1);
+	elba_spics_set_cs(dwselba, 1, 1);
+
+	dwsmmio->priv = dwselba;
+	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,
@@ -352,6 +436,7 @@ 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