pinctrl: starfive: Reset pinmux settings

Current u-boot doesn't seem to take into account that some GPIOs are
configured as inputs/outputs of certain peripherals on power-up. This
means it ends up configuring some GPIOs as inputs to more than one
peripheral which the documentation explicitly says is illegal. Similarly
it also ends up configuring more than one GPIO as output of the same
peripheral. While not explicitly mentioned by the documentation this
also seems like a bad idea.

The easiest way to remedy this mess is to just disconnect all GPIOs from
peripherals and have our pinmux configuration set everything up
properly. This, however, means that we'd disconnect the serial console
from its pins for a while, so add a device tree property to keep
certain GPIOs from being reset.

Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>

2 files changed, 70 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/pinctrl/starfive,jh7100-pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/starfive,jh7100-pinctrl.yaml
index f3258f2fd3a4..ce79d2ae3a32 100644
--- a/Documentation/devicetree/bindings/pinctrl/starfive,jh7100-pinctrl.yaml
+++ b/Documentation/devicetree/bindings/pinctrl/starfive,jh7100-pinctrl.yaml
@@ -88,6 +88,10 @@ properties:
     $ref: /schemas/types.yaml#/definitions/uint32
     enum: [0, 1, 2, 3, 4, 5, 6]
 
+  starfive,keep-gpiomux:
+    description: Keep pinmux for these GPIOs from being reset at boot.
+    $ref: /schemas/types.yaml#/definitions/uint32-array
+
 required:
   - compatible
   - reg
diff --git a/drivers/pinctrl/starfive/pinctrl-starfive-jh7100.c b/drivers/pinctrl/starfive/pinctrl-starfive-jh7100.c
index 6df7a310c7ed..13dd0745a32d 100644
--- a/drivers/pinctrl/starfive/pinctrl-starfive-jh7100.c
+++ b/drivers/pinctrl/starfive/pinctrl-starfive-jh7100.c
@@ -203,6 +203,10 @@ static u16 starfive_drive_strength_from_max_mA(u32 i)
 	return (clamp(i, 14U, 63U) - 14) / 7;
 }
 
+static bool keepmux;
+module_param(keepmux, bool, 0644);
+MODULE_PARM_DESC(keepmux, "Keep pinmux settings from previous boot stage");
+
 struct starfive_pinctrl {
 	struct gpio_chip gc;
 	struct pinctrl_gpio_range gpios;
@@ -1215,6 +1219,65 @@ static void starfive_disable_clock(void *data)
 	clk_disable_unprepare(data);
 }
 
+#define GPI_END (GPI_USB_OVER_CURRENT + 1)
+static void starfive_pinmux_reset(struct starfive_pinctrl *sfp)
+{
+	static const DECLARE_BITMAP(defaults, GPI_END) = {
+		BIT_MASK(GPI_I2C0_PAD_SCK_IN) |
+		BIT_MASK(GPI_I2C0_PAD_SDA_IN) |
+		BIT_MASK(GPI_I2C1_PAD_SCK_IN) |
+		BIT_MASK(GPI_I2C1_PAD_SDA_IN) |
+		BIT_MASK(GPI_I2C2_PAD_SCK_IN) |
+		BIT_MASK(GPI_I2C2_PAD_SDA_IN) |
+		BIT_MASK(GPI_I2C3_PAD_SCK_IN) |
+		BIT_MASK(GPI_I2C3_PAD_SDA_IN) |
+		BIT_MASK(GPI_SDIO0_PAD_CARD_DETECT_N) |
+
+		BIT_MASK(GPI_SDIO1_PAD_CARD_DETECT_N) |
+		BIT_MASK(GPI_SPI0_PAD_SS_IN_N) |
+		BIT_MASK(GPI_SPI1_PAD_SS_IN_N) |
+		BIT_MASK(GPI_SPI2_PAD_SS_IN_N) |
+		BIT_MASK(GPI_SPI2AHB_PAD_SS_N) |
+		BIT_MASK(GPI_SPI3_PAD_SS_IN_N),
+
+		BIT_MASK(GPI_UART0_PAD_SIN) |
+		BIT_MASK(GPI_UART1_PAD_SIN) |
+		BIT_MASK(GPI_UART2_PAD_SIN) |
+		BIT_MASK(GPI_UART3_PAD_SIN) |
+		BIT_MASK(GPI_USB_OVER_CURRENT)
+	};
+	DECLARE_BITMAP(keep, NR_GPIOS) = {};
+	struct device_node *np = sfp->gc.parent->of_node;
+	int len = of_property_count_u32_elems(np, "starfive,keep-gpiomux");
+	int i;
+
+	for (i = 0; i < len; i++) {
+		u32 gpio;
+
+		of_property_read_u32_index(np, "starfive,keep-gpiomux", i, &gpio);
+		if (gpio < NR_GPIOS)
+			set_bit(gpio, keep);
+	}
+
+	for (i = 0; i < NR_GPIOS; i++) {
+		if (test_bit(i, keep))
+			continue;
+
+		writel_relaxed(GPO_DISABLE, sfp->base + GPON_DOEN_CFG + 8 * i);
+		writel_relaxed(GPO_LOW,     sfp->base + GPON_DOUT_CFG + 8 * i);
+	}
+
+	for (i = 0; i < GPI_END; i++) {
+		void __iomem *reg = sfp->base + GPI_CFG_OFFSET + 4 * i;
+		u32 din = readl_relaxed(reg);
+
+		if (din >= 2 && din < (NR_GPIOS + 2) && test_bit(din - 2, keep))
+			continue;
+
+		writel_relaxed(test_bit(i, defaults), reg);
+	}
+}
+
 static int starfive_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -1276,6 +1339,9 @@ static int starfive_probe(struct platform_device *pdev)
 		writel(value, sfp->padctl + IO_PADSHARE_SEL);
 	}
 
+	if (!keepmux)
+		starfive_pinmux_reset(sfp);
+
 	value = readl(sfp->padctl + IO_PADSHARE_SEL);
 	switch (value) {
 	case 0: