clk: xilinx: vcu: Update vcu init/reset sequence

Updated vcu init/reset sequence as per design changes.
If VCU reset GPIO is available then do assert and de-assert it before
enabling/disabling gasket isolation.
This GPIO is added because gasket isolation will be removed during startup
that requires access to SLCR register space. Post startup, the ownership of
the register interface lies with logiCORE IP.

Signed-off-by: Rohit Visavalia <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Stephen Boyd <[email protected]>

Author: rohitvisavalia

drivers/clk/xilinx/xlnx_vcu.c

@@ -11,6 +11,7 @@
 #include <linux/clk-provider.h>
 #include <linux/device.h>
 #include <linux/errno.h>
+#include <linux/gpio/consumer.h>
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
 #include <linux/mfd/syscon/xlnx-vcu.h>
@@ -51,6 +52,7 @@
  * @dev: Platform device
  * @pll_ref: pll ref clock source
  * @aclk: axi clock source
+ * @reset_gpio: vcu reset gpio
  * @logicore_reg_ba: logicore reg base address
  * @vcu_slcr_ba: vcu_slcr Register base address
  * @pll: handle for the VCU PLL
@@ -61,6 +63,7 @@ struct xvcu_device {
 	struct device *dev;
 	struct clk *pll_ref;
 	struct clk *aclk;
+	struct gpio_desc *reset_gpio;
 	struct regmap *logicore_reg_ba;
 	void __iomem *vcu_slcr_ba;
 	struct clk_hw *pll;
@@ -676,6 +679,24 @@ static int xvcu_probe(struct platform_device *pdev)
 	 * Bit 0 : Gasket isolation
 	 * Bit 1 : put VCU out of reset
 	 */
+	xvcu->reset_gpio = devm_gpiod_get_optional(&pdev->dev, "reset",
+						   GPIOD_OUT_LOW);
+	if (IS_ERR(xvcu->reset_gpio)) {
+		ret = PTR_ERR(xvcu->reset_gpio);
+		dev_err_probe(&pdev->dev, ret, "failed to get reset gpio for vcu.\n");
+		goto error_get_gpio;
+	}
+
+	if (xvcu->reset_gpio) {
+		gpiod_set_value(xvcu->reset_gpio, 0);
+		/* min 2 clock cycle of vcu pll_ref, slowest freq is 33.33KHz */
+		usleep_range(60, 120);
+		gpiod_set_value(xvcu->reset_gpio, 1);
+		usleep_range(60, 120);
+	} else {
+		dev_dbg(&pdev->dev, "No reset gpio info found in dts for VCU. This may result in incorrect functionality if VCU isolation is removed after initialization in designs where the VCU reset is driven by gpio.\n");
+	}
+
 	regmap_write(xvcu->logicore_reg_ba, VCU_GASKET_INIT, VCU_GASKET_VALUE);
 
 	ret = xvcu_register_clock_provider(xvcu);
@@ -690,6 +711,7 @@ static int xvcu_probe(struct platform_device *pdev)
 
 error_clk_provider:
 	xvcu_unregister_clock_provider(xvcu);
+error_get_gpio:
 	clk_disable_unprepare(xvcu->aclk);
 	return ret;
 }
@@ -711,6 +733,13 @@ static void xvcu_remove(struct platform_device *pdev)
 	xvcu_unregister_clock_provider(xvcu);
 
 	/* Add the Gasket isolation and put the VCU in reset. */
+	if (xvcu->reset_gpio) {
+		gpiod_set_value(xvcu->reset_gpio, 0);
+		/* min 2 clock cycle of vcu pll_ref, slowest freq is 33.33KHz */
+		usleep_range(60, 120);
+		gpiod_set_value(xvcu->reset_gpio, 1);
+		usleep_range(60, 120);
+	}
 	regmap_write(xvcu->logicore_reg_ba, VCU_GASKET_INIT, 0);
 
 	clk_disable_unprepare(xvcu->aclk);