reset: Add Broadcom STB RESCAL reset controller

On BCM7216 there is a special purpose reset controller named RESCAL
(reset calibration) which is necessary for SATA and PCIe0/1 to operate
correctly. This commit adds support for such a reset controller to be
available.

Signed-off-by: Jim Quinlan <jim2101024@gmail.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/reset/Kconfig

@@ -49,6 +49,13 @@ config RESET_BRCMSTB
 	  This enables the reset controller driver for Broadcom STB SoCs using
 	  a SUN_TOP_CTRL_SW_INIT style controller.
 
+config RESET_BRCMSTB_RESCAL
+	bool "Broadcom STB RESCAL reset controller"
+	default ARCH_BRCMSTB || COMPILE_TEST
+	help
+	  This enables the RESCAL reset controller for SATA, PCIe0, or PCIe1 on
+	  BCM7216.
+
 config RESET_HSDK
 	bool "Synopsys HSDK Reset Driver"
 	depends on HAS_IOMEM

drivers/reset/Makefile

@@ -8,6 +8,7 @@ obj-$(CONFIG_RESET_ATH79) += reset-ath79.o
 obj-$(CONFIG_RESET_AXS10X) += reset-axs10x.o
 obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
 obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o
+obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
 obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
 obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o

drivers/reset/reset-brcmstb-rescal.c

@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2018-2020 Broadcom */
+
+#include <linux/device.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+
+#define BRCM_RESCAL_START	0x0
+#define  BRCM_RESCAL_START_BIT	BIT(0)
+#define BRCM_RESCAL_CTRL	0x4
+#define BRCM_RESCAL_STATUS	0x8
+#define  BRCM_RESCAL_STATUS_BIT	BIT(0)
+
+struct brcm_rescal_reset {
+	void __iomem *base;
+	struct device *dev;
+	struct reset_controller_dev rcdev;
+};
+
+static int brcm_rescal_reset_set(struct reset_controller_dev *rcdev,
+				 unsigned long id)
+{
+	struct brcm_rescal_reset *data =
+		container_of(rcdev, struct brcm_rescal_reset, rcdev);
+	void __iomem *base = data->base;
+	u32 reg;
+	int ret;
+
+	reg = readl(base + BRCM_RESCAL_START);
+	writel(reg | BRCM_RESCAL_START_BIT, base + BRCM_RESCAL_START);
+	reg = readl(base + BRCM_RESCAL_START);
+	if (!(reg & BRCM_RESCAL_START_BIT)) {
+		dev_err(data->dev, "failed to start SATA/PCIe rescal\n");
+		return -EIO;
+	}
+
+	ret = readl_poll_timeout(base + BRCM_RESCAL_STATUS, reg,
+				 !(reg & BRCM_RESCAL_STATUS_BIT), 100, 1000);
+	if (ret) {
+		dev_err(data->dev, "time out on SATA/PCIe rescal\n");
+		return ret;
+	}
+
+	reg = readl(base + BRCM_RESCAL_START);
+	writel(reg & ~BRCM_RESCAL_START_BIT, base + BRCM_RESCAL_START);
+
+	dev_dbg(data->dev, "SATA/PCIe rescal success\n");
+
+	return 0;
+}
+
+static int brcm_rescal_reset_xlate(struct reset_controller_dev *rcdev,
+				   const struct of_phandle_args *reset_spec)
+{
+	/* This is needed if #reset-cells == 0. */
+	return 0;
+}
+
+static const struct reset_control_ops brcm_rescal_reset_ops = {
+	.reset = brcm_rescal_reset_set,
+};
+
+static int brcm_rescal_reset_probe(struct platform_device *pdev)
+{
+	struct brcm_rescal_reset *data;
+	struct resource *res;
+
+	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	data->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(data->base))
+		return PTR_ERR(data->base);
+
+	data->rcdev.owner = THIS_MODULE;
+	data->rcdev.nr_resets = 1;
+	data->rcdev.ops = &brcm_rescal_reset_ops;
+	data->rcdev.of_node = pdev->dev.of_node;
+	data->rcdev.of_xlate = brcm_rescal_reset_xlate;
+	data->dev = &pdev->dev;
+
+	return devm_reset_controller_register(&pdev->dev, &data->rcdev);
+}
+
+static const struct of_device_id brcm_rescal_reset_of_match[] = {
+	{ .compatible = "brcm,bcm7216-pcie-sata-rescal" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, brcm_rescal_reset_of_match);
+
+static struct platform_driver brcm_rescal_reset_driver = {
+	.probe = brcm_rescal_reset_probe,
+	.driver = {
+		.name	= "brcm-rescal-reset",
+		.of_match_table	= brcm_rescal_reset_of_match,
+	}
+};
+module_platform_driver(brcm_rescal_reset_driver);
+
+MODULE_AUTHOR("Broadcom");
+MODULE_DESCRIPTION("Broadcom SATA/PCIe rescal reset controller");
+MODULE_LICENSE("GPL v2");