[PATCH net-next 09/16] net: mdio: Add Synopsys DW XPCS management interface support

[Serge Semin <fancer.lancer@gmail.com>]

Synopsys DesignWare XPCS IP-core can be synthesized with the device CSRs
being accessible over MCI or APB3 interface instead of the MDIO bus (see
the CSR_INTERFACE HDL parameter). Thus all the PCS registers can be just
memory mapped and be a subject of standard MMIO operations of course
taking into account the way the Clause C45 CSRs mapping is defined. This
commit is about adding a device driver for the DW XPCS Management
Interface platform device and registering it in the framework of the
kernel MDIO subsystem.

DW XPCS platform device is supposed to be described by the respective
compatible string "snps,dw-xpcs-mi", CSRs memory space and optional
peripheral bus clock source. Note depending on the INDIRECT_ACCESS DW XPCS
IP-core synthesize parameter the memory-mapped reg-space can be
represented as either directly or indirectly mapped Clause 45 space. In
the former case the particular address is determined based on the MMD
device and the registers offset (5 + 16 bits all together) within the
device reg-space. In the later case there is only 256 lower address bits
are utilized for the registers mapping. The upper bits are supposed to be
written into the respective viewport CSR in order to reach the entire C45
space.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
---
 drivers/net/mdio/Kconfig        |   8 +
 drivers/net/mdio/Makefile       |   1 +
 drivers/net/mdio/mdio-dw-xpcs.c | 384 ++++++++++++++++++++++++++++++++
 3 files changed, 393 insertions(+)
 create mode 100644 drivers/net/mdio/mdio-dw-xpcs.c

diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
index 4a7a303be2f7..39f7ce8087bf 100644
--- a/drivers/net/mdio/Kconfig
+++ b/drivers/net/mdio/Kconfig
@@ -185,6 +185,14 @@ config MDIO_IPQ8064
 	  This driver supports the MDIO interface found in the network
 	  interface units of the IPQ8064 SoC
 
+config MDIO_DW_XPCS
+	tristate "Synopsys DesignWare XPCS MI bus support"
+	depends on HAS_IOMEM
+	select MDIO_DEVRES
+	help
+	  This driver supports the MCI/APB3 Management Interface responsible
+	  for communicating with the Synopsys DesignWare XPCS devices.
+
 config MDIO_REGMAP
 	tristate
 	help
diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
index 1015f0db4531..6389d4c3b862 100644
--- a/drivers/net/mdio/Makefile
+++ b/drivers/net/mdio/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_MDIO_BCM_IPROC)		+= mdio-bcm-iproc.o
 obj-$(CONFIG_MDIO_BCM_UNIMAC)		+= mdio-bcm-unimac.o
 obj-$(CONFIG_MDIO_BITBANG)		+= mdio-bitbang.o
 obj-$(CONFIG_MDIO_CAVIUM)		+= mdio-cavium.o
+obj-$(CONFIG_MDIO_DW_XPCS)		+= mdio-dw-xpcs.o
 obj-$(CONFIG_MDIO_GPIO)			+= mdio-gpio.o
 obj-$(CONFIG_MDIO_HISI_FEMAC)		+= mdio-hisi-femac.o
 obj-$(CONFIG_MDIO_I2C)			+= mdio-i2c.o
diff --git a/drivers/net/mdio/mdio-dw-xpcs.c b/drivers/net/mdio/mdio-dw-xpcs.c
new file mode 100644
index 000000000000..c47f0a54d31b
--- /dev/null
+++ b/drivers/net/mdio/mdio-dw-xpcs.c
@@ -0,0 +1,384 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Synopsys DesignWare XPCS Management Interface driver
+ *
+ * Copyright (C) 2023 BAIKAL ELECTRONICS, JSC
+ */
+
+#include <linux/atomic.h>
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/mdio.h>
+#include <linux/module.h>
+#include <linux/of_mdio.h>
+#include <linux/phy.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/property.h>
+#include <linux/sizes.h>
+
+/* Page select register for the indirect MMIO CSRs access */
+#define DW_VR_CSR_VIEWPORT		0xff
+
+struct dw_xpcs_mi {
+	struct platform_device *pdev;
+	struct mii_bus *bus;
+	bool reg_indir;
+	int reg_width;
+	void __iomem *reg_base;
+	struct clk *pclk;
+};
+
+static inline ptrdiff_t dw_xpcs_mmio_addr_format(int dev, int reg)
+{
+	return FIELD_PREP(0x1f0000, dev) | FIELD_PREP(0xffff, reg);
+}
+
+static inline u16 dw_xpcs_mmio_addr_page(ptrdiff_t csr)
+{
+	return FIELD_GET(0x1fff00, csr);
+}
+
+static inline ptrdiff_t dw_xpcs_mmio_addr_offset(ptrdiff_t csr)
+{
+	return FIELD_GET(0xff, csr);
+}
+
+static int dw_xpcs_mmio_read_reg_indirect(struct dw_xpcs_mi *dxmi,
+					  int dev, int reg)
+{
+	ptrdiff_t csr, ofs;
+	u16 page;
+	int ret;
+
+	csr = dw_xpcs_mmio_addr_format(dev, reg);
+	page = dw_xpcs_mmio_addr_page(csr);
+	ofs = dw_xpcs_mmio_addr_offset(csr);
+
+	ret = pm_runtime_resume_and_get(&dxmi->pdev->dev);
+	if (ret)
+		return ret;
+
+	switch (dxmi->reg_width) {
+	case 4:
+		writel(page, dxmi->reg_base + (DW_VR_CSR_VIEWPORT << 2));
+		ret = readl(dxmi->reg_base + (ofs << 2));
+		break;
+	default:
+		writew(page, dxmi->reg_base + (DW_VR_CSR_VIEWPORT << 1));
+		ret = readw(dxmi->reg_base + (ofs << 1));
+		break;
+	}
+
+	pm_runtime_put(&dxmi->pdev->dev);
+
+	return ret;
+}
+
+static int dw_xpcs_mmio_write_reg_indirect(struct dw_xpcs_mi *dxmi,
+					   int dev, int reg, u16 val)
+{
+	ptrdiff_t csr, ofs;
+	u16 page;
+	int ret;
+
+	csr = dw_xpcs_mmio_addr_format(dev, reg);
+	page = dw_xpcs_mmio_addr_page(csr);
+	ofs = dw_xpcs_mmio_addr_offset(csr);
+
+	ret = pm_runtime_resume_and_get(&dxmi->pdev->dev);
+	if (ret)
+		return ret;
+
+	switch (dxmi->reg_width) {
+	case 4:
+		writel(page, dxmi->reg_base + (DW_VR_CSR_VIEWPORT << 2));
+		writel(val, dxmi->reg_base + (ofs << 2));
+		break;
+	default:
+		writew(page, dxmi->reg_base + (DW_VR_CSR_VIEWPORT << 1));
+		writew(val, dxmi->reg_base + (ofs << 1));
+		break;
+	}
+
+	pm_runtime_put(&dxmi->pdev->dev);
+
+	return 0;
+}
+
+static int dw_xpcs_mmio_read_reg_direct(struct dw_xpcs_mi *dxmi,
+					int dev, int reg)
+{
+	ptrdiff_t csr;
+	int ret;
+
+	csr = dw_xpcs_mmio_addr_format(dev, reg);
+
+	ret = pm_runtime_resume_and_get(&dxmi->pdev->dev);
+	if (ret)
+		return ret;
+
+	switch (dxmi->reg_width) {
+	case 4:
+		ret = readl(dxmi->reg_base + (csr << 2));
+		break;
+	default:
+		ret = readw(dxmi->reg_base + (csr << 1));
+		break;
+	}
+
+	pm_runtime_put(&dxmi->pdev->dev);
+
+	return ret;
+}
+
+static int dw_xpcs_mmio_write_reg_direct(struct dw_xpcs_mi *dxmi,
+					 int dev, int reg, u16 val)
+{
+	ptrdiff_t csr;
+	int ret;
+
+	csr = dw_xpcs_mmio_addr_format(dev, reg);
+
+	ret = pm_runtime_resume_and_get(&dxmi->pdev->dev);
+	if (ret)
+		return ret;
+
+	switch (dxmi->reg_width) {
+	case 4:
+		writel(val, dxmi->reg_base + (csr << 2));
+		break;
+	default:
+		writew(val, dxmi->reg_base + (csr << 1));
+		break;
+	}
+
+	pm_runtime_put(&dxmi->pdev->dev);
+
+	return 0;
+}
+
+static int dw_xpcs_mmio_read_c22(struct mii_bus *bus, int addr, int reg)
+{
+	struct dw_xpcs_mi *dxmi = bus->priv;
+
+	if (addr != 0)
+		return -ENODEV;
+
+	if (dxmi->reg_indir)
+		return dw_xpcs_mmio_read_reg_indirect(dxmi, MDIO_MMD_VEND2, reg);
+	else
+		return dw_xpcs_mmio_read_reg_direct(dxmi, MDIO_MMD_VEND2, reg);
+}
+
+static int dw_xpcs_mmio_write_c22(struct mii_bus *bus, int addr, int reg, u16 val)
+{
+	struct dw_xpcs_mi *dxmi = bus->priv;
+
+	if (addr != 0)
+		return -ENODEV;
+
+	if (dxmi->reg_indir)
+		return dw_xpcs_mmio_write_reg_indirect(dxmi, MDIO_MMD_VEND2, reg, val);
+	else
+		return dw_xpcs_mmio_write_reg_direct(dxmi, MDIO_MMD_VEND2, reg, val);
+}
+
+static int dw_xpcs_mmio_read_c45(struct mii_bus *bus, int addr, int dev, int reg)
+{
+	struct dw_xpcs_mi *dxmi = bus->priv;
+
+	if (addr != 0)
+		return -ENODEV;
+
+	if (dxmi->reg_indir)
+		return dw_xpcs_mmio_read_reg_indirect(dxmi, dev, reg);
+	else
+		return dw_xpcs_mmio_read_reg_direct(dxmi, dev, reg);
+}
+
+static int dw_xpcs_mmio_write_c45(struct mii_bus *bus, int addr, int dev,
+				  int reg, u16 val)
+{
+	struct dw_xpcs_mi *dxmi = bus->priv;
+
+	if (addr != 0)
+		return -ENODEV;
+
+	if (dxmi->reg_indir)
+		return dw_xpcs_mmio_write_reg_indirect(dxmi, dev, reg, val);
+	else
+		return dw_xpcs_mmio_write_reg_direct(dxmi, dev, reg, val);
+}
+
+static struct dw_xpcs_mi *dw_xpcs_mi_create_data(struct platform_device *pdev)
+{
+	struct dw_xpcs_mi *dxmi;
+
+	dxmi = devm_kzalloc(&pdev->dev, sizeof(*dxmi), GFP_KERNEL);
+	if (!dxmi)
+		return ERR_PTR(-ENOMEM);
+
+	dxmi->pdev = pdev;
+
+	dev_set_drvdata(&pdev->dev, dxmi);
+
+	return dxmi;
+}
+
+static int dw_xpcs_mi_init_res(struct dw_xpcs_mi *dxmi)
+{
+	struct device *dev = &dxmi->pdev->dev;
+	struct resource *res;
+
+	if (!device_property_read_u32(dev, "reg-io-width", &dxmi->reg_width)) {
+		if (dxmi->reg_width != 2 && dxmi->reg_width != 4) {
+			dev_err(dev, "Invalid regspace data width\n");
+			return -EINVAL;
+		}
+	} else {
+		dxmi->reg_width = 2;
+	}
+
+	res = platform_get_resource_byname(dxmi->pdev, IORESOURCE_MEM, "direct") ?:
+	      platform_get_resource_byname(dxmi->pdev, IORESOURCE_MEM, "indirect");
+	if (!res) {
+		dev_err(dev, "No regspace found\n");
+		return -EINVAL;
+	}
+
+	if (!strcmp(res->name, "indirect"))
+		dxmi->reg_indir = true;
+
+	if ((dxmi->reg_indir && resource_size(res) < dxmi->reg_width * SZ_256) ||
+	    (!dxmi->reg_indir && resource_size(res) < dxmi->reg_width * SZ_2M)) {
+		dev_err(dev, "Invalid regspace size\n");
+		return -EINVAL;
+	}
+
+	dxmi->reg_base = devm_ioremap_resource(dev, res);
+	if (IS_ERR(dxmi->reg_base)) {
+		dev_err(dev, "Failed to map regspace\n");
+		return PTR_ERR(dxmi->reg_base);
+	}
+
+	return 0;
+}
+
+static int dw_xpcs_mi_init_clk(struct dw_xpcs_mi *dxmi)
+{
+	struct device *dev = &dxmi->pdev->dev;
+	int ret;
+
+	dxmi->pclk = devm_clk_get_optional(dev, "pclk");
+        if (IS_ERR(dxmi->pclk))
+		return dev_err_probe(dev, PTR_ERR(dxmi->pclk),
+				     "Failed to get ref clock\n");
+
+	pm_runtime_set_active(dev);
+	ret = devm_pm_runtime_enable(dev);
+	if (ret) {
+		dev_err(dev, "Failed to enable runtime-PM\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int dw_xpcs_mi_init_mdio(struct dw_xpcs_mi *dxmi)
+{
+	struct device *dev = &dxmi->pdev->dev;
+	static atomic_t id = ATOMIC_INIT(-1);
+	int ret;
+
+	dxmi->bus = devm_mdiobus_alloc_size(dev, 0);
+	if (!dxmi->bus)
+		return -ENOMEM;
+
+	dxmi->bus->name = "DW XPCS MI";
+	dxmi->bus->read = dw_xpcs_mmio_read_c22;
+	dxmi->bus->write = dw_xpcs_mmio_write_c22;
+	dxmi->bus->read_c45 = dw_xpcs_mmio_read_c45;
+	dxmi->bus->write_c45 = dw_xpcs_mmio_write_c45;
+	dxmi->bus->phy_mask = ~0;
+	dxmi->bus->parent = dev;
+	dxmi->bus->priv = dxmi;
+
+	snprintf(dxmi->bus->id, MII_BUS_ID_SIZE,
+		 "dwxpcs-%x", atomic_inc_return(&id));
+
+	ret = devm_of_mdiobus_register(dev, dxmi->bus, dev_of_node(dev));
+	if (ret) {
+		dev_err(dev, "Failed to create MDIO bus\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int dw_xpcs_mi_probe(struct platform_device *pdev)
+{
+	struct dw_xpcs_mi *dxmi;
+	int ret;
+
+	dxmi = dw_xpcs_mi_create_data(pdev);
+	if (IS_ERR(dxmi))
+		return PTR_ERR(dxmi);
+
+	ret = dw_xpcs_mi_init_res(dxmi);
+	if (ret)
+		return ret;
+
+	ret = dw_xpcs_mi_init_clk(dxmi);
+	if (ret)
+		return ret;
+
+	ret = dw_xpcs_mi_init_mdio(dxmi);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int __maybe_unused dw_xpcs_mi_pm_runtime_suspend(struct device *dev)
+{
+	struct dw_xpcs_mi *dxmi = dev_get_drvdata(dev);
+
+	clk_disable_unprepare(dxmi->pclk);
+
+	return 0;
+}
+
+static int __maybe_unused dw_xpcs_mi_pm_runtime_resume(struct device *dev)
+{
+	struct dw_xpcs_mi *dxmi = dev_get_drvdata(dev);
+
+	return clk_prepare_enable(dxmi->pclk);
+}
+
+const struct dev_pm_ops dw_xpcs_mi_pm_ops = {
+        SET_RUNTIME_PM_OPS(dw_xpcs_mi_pm_runtime_suspend, dw_xpcs_mi_pm_runtime_resume, NULL)
+};
+
+static const struct of_device_id dw_xpcs_mi_of_ids[] = {
+	{ .compatible = "snps,dw-xpcs-mi" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, dw_xpcs_mi_of_ids);
+
+static struct platform_driver dw_xpcs_mi_driver = {
+	.probe = dw_xpcs_mi_probe,
+	.driver = {
+		.name = "dw-xpcs-mi",
+		.pm = &dw_xpcs_mi_pm_ops,
+		.of_match_table = dw_xpcs_mi_of_ids,
+	},
+};
+
+module_platform_driver(dw_xpcs_mi_driver);
+
+MODULE_DESCRIPTION("Synopsys DesignWare XPCS Management Interface driver");
+MODULE_AUTHOR("Serge Semin <Sergey.Semin@baikalelectronics.ru>");
+MODULE_LICENSE("GPL v2");
-- 
2.42.1