linux-kernel - [PATCH v6 12/17] spi: dw: Add support for AMD Pensando Elba SoC

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Message-Id: <20220820195750.70861-13-brad@pensando.io>
Date:   Sat, 20 Aug 2022 12:57:45 -0700
From:   Brad Larson <brad@...sando.io>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
        adrian.hunter@...el.com, alcooperx@...il.com,
        andy.shevchenko@...il.com, arnd@...db.de, brad@...sando.io,
        blarson@....com, brijeshkumar.singh@....com,
        catalin.marinas@....com, gsomlo@...il.com, gerg@...ux-m68k.org,
        krzk@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        lee.jones@...aro.org, broonie@...nel.org,
        yamada.masahiro@...ionext.com, p.zabel@...gutronix.de,
        piotrs@...ence.com, p.yadav@...com, rdunlap@...radead.org,
        robh+dt@...nel.org, samuel@...lland.org, fancer.lancer@...il.com,
        suravee.suthikulpanit@....com, thomas.lendacky@....com,
        ulf.hansson@...aro.org, will@...nel.org, devicetree@...r.kernel.org
Subject: [PATCH v6 12/17] spi: dw: Add support for AMD Pensando Elba SoC

From: Brad Larson <blarson@....com>

The AMD 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 <blarson@....com>
---
 drivers/spi/spi-dw-mmio.c | 77 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

diff --git a/drivers/spi/spi-dw-mmio.c b/drivers/spi/spi-dw-mmio.c
index 26c40ea6dd12..36b8c5e10bb3 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 *syscon;
+};
+
+/*
+ * 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_REG			0x2468
+#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
@@ -237,6 +255,64 @@ static int dw_spi_canaan_k210_init(struct platform_device *pdev,
 	return 0;
 }
 
+static void dw_spi_elba_override_cs(struct dw_spi_elba *dwselba, int cs, int enable)
+{
+	regmap_update_bits(dwselba->syscon, ELBA_SPICS_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)
+		dw_spi_elba_override_cs(dwselba, spi->chip_select, enable);
+
+	/*
+	 * The DW SPI controller needs a native CS bit selected to start
+	 * the serial engine.
+	 */
+	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)
+{
+	const char *syscon_name = "amd,pensando-elba-syscon";
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *node;
+	struct dw_spi_elba *dwselba;
+	struct regmap *regmap;
+
+	node = of_parse_phandle(np, syscon_name, 0);
+	if (!node) {
+		dev_err(&pdev->dev, "failed to find %s\n", syscon_name);
+		return -ENODEV;
+	}
+
+	regmap = syscon_node_to_regmap(node);
+	if (IS_ERR(regmap)) {
+		dev_err(&pdev->dev, "syscon regmap lookup failed\n");
+		return PTR_ERR(regmap);
+	}
+
+	dwselba = devm_kzalloc(&pdev->dev, sizeof(*dwselba), GFP_KERNEL);
+	if (!dwselba)
+		return -ENOMEM;
+
+	dwselba->syscon = regmap;
+	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 +428,7 @@ static const struct of_device_id dw_spi_mmio_of_match[] = {
 	{ .compatible = "intel,thunderbay-ssi", .data = dw_spi_intel_init},
 	{ .compatible = "microchip,sparx5-spi", dw_spi_mscc_sparx5_init},
 	{ .compatible = "canaan,k210-spi", dw_spi_canaan_k210_init},
+	{ .compatible = "amd,pensando-elba-spi", .data = dw_spi_elba_init},
 	{ /* end of table */}
 };
 MODULE_DEVICE_TABLE(of, dw_spi_mmio_of_match);
-- 
2.17.1