[PATCH RFC net-next 4/9] net: pcs: xpcs: add Qualcomm Nord platform support

[Mohd Ayaan Anwar <mohd.anwar@oss.qualcomm.com>]

Qualcomm Nord exposes the DesignWare XPCS register blocks through
separate direct-MMIO windows instead of the standard contiguous
MMD/register layout. Add accessors that translate MMD accesses to the
Nord windows:

  MMD 3 (PCS), standard registers: SR_XS at 0x0000
  MMD 3 (PCS), vendor registers:   VR_XS at 0x2000
  MMD 1 (PMA/PMD):                  SR_PMA at 0x3000
  MMD 31 (VEND2), standard regs:    SR_MII at 0x4000
  MMD 31 (VEND2), vendor registers: VR_MII at 0x5000

Each register uses a 32-bit MMIO stride. The vendor bit is removed from
the register index before calculating a vendor-window offset.

Select these accessors using the Nord synthetic XPCS ID, allow its
smaller direct-MMIO resource, and add the Nord USXGMII Clause 37
compatibility.

Signed-off-by: Mohd Ayaan Anwar <mohd.anwar@oss.qualcomm.com>
---
 drivers/net/pcs/Makefile        |  3 +-
 drivers/net/pcs/pcs-xpcs-plat.c | 17 +++++++-
 drivers/net/pcs/pcs-xpcs-qcom.c | 86 +++++++++++++++++++++++++++++++++++++++++
 drivers/net/pcs/pcs-xpcs-qcom.h | 16 ++++++++
 drivers/net/pcs/pcs-xpcs.c      | 13 +++++++
 include/linux/pcs/pcs-xpcs.h    |  1 +
 6 files changed, 134 insertions(+), 2 deletions(-)

diff --git a/drivers/net/pcs/Makefile b/drivers/net/pcs/Makefile
index 4f7920618b90051e839a74a7101aaaf055a77f74..3d7cf1a5cd0783078edcefc6dfec626af469495d 100644
--- a/drivers/net/pcs/Makefile
+++ b/drivers/net/pcs/Makefile
@@ -2,7 +2,8 @@
 # Makefile for Linux PCS drivers
 
 pcs_xpcs-$(CONFIG_PCS_XPCS)	:= pcs-xpcs.o pcs-xpcs-plat.o \
-				   pcs-xpcs-nxp.o pcs-xpcs-wx.o
+				   pcs-xpcs-nxp.o pcs-xpcs-qcom.o \
+				   pcs-xpcs-wx.o
 
 obj-$(CONFIG_PCS_XPCS)		+= pcs_xpcs.o
 obj-$(CONFIG_PCS_LYNX)		+= pcs-lynx.o
diff --git a/drivers/net/pcs/pcs-xpcs-plat.c b/drivers/net/pcs/pcs-xpcs-plat.c
index e78a233fb198d940951064a71e8597c6c666bc9d..e013a5253a22651220e62352d03faabc3a3c3658 100644
--- a/drivers/net/pcs/pcs-xpcs-plat.c
+++ b/drivers/net/pcs/pcs-xpcs-plat.c
@@ -20,6 +20,7 @@
 #include <linux/sizes.h>
 
 #include "pcs-xpcs.h"
+#include "pcs-xpcs-qcom.h"
 
 /* Page select register for the indirect MMIO CSRs access */
 #define DW_VR_CSR_VIEWPORT		0xff
@@ -239,8 +240,14 @@ static int xpcs_mmio_write_c45(struct mii_bus *bus, int addr, int dev,
 		return xpcs_mmio_write_reg_direct(pxpcs, dev, reg, val);
 }
 
+static const struct dw_xpcs_plat_ops xpcs_qcom_ops = {
+	.reg_read = xpcs_qcom_reg_read,
+	.reg_write = xpcs_qcom_reg_write,
+};
+
 static struct dw_xpcs_plat *xpcs_plat_create_data(struct platform_device *pdev)
 {
+	const struct dw_xpcs_info *info;
 	struct dw_xpcs_plat *pxpcs;
 
 	pxpcs = devm_kzalloc(&pdev->dev, sizeof(*pxpcs), GFP_KERNEL);
@@ -248,6 +255,12 @@ static struct dw_xpcs_plat *xpcs_plat_create_data(struct platform_device *pdev)
 		return ERR_PTR(-ENOMEM);
 
 	pxpcs->pdev = pdev;
+	info = device_get_match_data(&pdev->dev);
+	if (!info)
+		return ERR_PTR(-EINVAL);
+
+	if (info->pcs == QCOM_NORD_XPCS_ID)
+		pxpcs->ops = &xpcs_qcom_ops;
 
 	dev_set_drvdata(&pdev->dev, pxpcs);
 
@@ -285,7 +298,7 @@ static int xpcs_plat_init_res(struct dw_xpcs_plat *pxpcs)
 	else
 		spc_size = pxpcs->reg_width * SZ_2M;
 
-	if (resource_size(res) < spc_size) {
+	if (!pxpcs->ops && resource_size(res) < spc_size) {
 		dev_err(dev, "Invalid reg-space size\n");
 		return -EINVAL;
 	}
@@ -452,8 +465,10 @@ DW_XPCS_INFO_DECLARE(xpcs_pma_gen4_3g, DW_XPCS_ID_NATIVE, DW_XPCS_PMA_GEN4_3G_ID
 DW_XPCS_INFO_DECLARE(xpcs_pma_gen4_6g, DW_XPCS_ID_NATIVE, DW_XPCS_PMA_GEN4_6G_ID);
 DW_XPCS_INFO_DECLARE(xpcs_pma_gen5_10g, DW_XPCS_ID_NATIVE, DW_XPCS_PMA_GEN5_10G_ID);
 DW_XPCS_INFO_DECLARE(xpcs_pma_gen5_12g, DW_XPCS_ID_NATIVE, DW_XPCS_PMA_GEN5_12G_ID);
+DW_XPCS_INFO_DECLARE(xpcs_qcom_nord, QCOM_NORD_XPCS_ID, DW_XPCS_PMA_ID_NATIVE);
 
 static const struct of_device_id xpcs_of_ids[] = {
+	{ .compatible = "qcom,nord-dw-xpcs", .data = &xpcs_qcom_nord },
 	{ .compatible = "snps,dw-xpcs", .data = &xpcs_generic },
 	{ .compatible = "snps,dw-xpcs-gen1-3g", .data = &xpcs_pma_gen1_3g },
 	{ .compatible = "snps,dw-xpcs-gen2-3g", .data = &xpcs_pma_gen2_3g },
diff --git a/drivers/net/pcs/pcs-xpcs-qcom.c b/drivers/net/pcs/pcs-xpcs-qcom.c
new file mode 100644
index 0000000000000000000000000000000000000000..63c95c951454819b62eb3fd00abcc6b529e2004b
--- /dev/null
+++ b/drivers/net/pcs/pcs-xpcs-qcom.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Qualcomm DesignWare XPCS platform helpers
+ *
+ * Copyright (c) 2026 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/io.h>
+#include <linux/mdio.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+
+#include "pcs-xpcs.h"
+#include "pcs-xpcs-qcom.h"
+
+/* Qualcomm Nord direct MMIO XPCS windows. */
+#define QCOM_XPCS_SR_XS_BASE		0x0000
+#define QCOM_XPCS_VR_XS_BASE		0x2000
+#define QCOM_XPCS_SR_PMA_BASE		0x3000
+#define QCOM_XPCS_SR_MII_BASE		0x4000
+#define QCOM_XPCS_VR_MII_BASE		0x5000
+
+static int xpcs_qcom_reg_offset(int dev, int reg)
+{
+	switch (dev) {
+	case MDIO_MMD_PCS:
+		if (reg & DW_VENDOR)
+			return QCOM_XPCS_VR_XS_BASE +
+			       ((reg & ~DW_VENDOR) << 2);
+
+		return QCOM_XPCS_SR_XS_BASE + (reg << 2);
+
+	case MDIO_MMD_PMAPMD:
+		return QCOM_XPCS_SR_PMA_BASE + (reg << 2);
+
+	case MDIO_MMD_VEND2:
+		if (reg >= DW_VENDOR)
+			return QCOM_XPCS_VR_MII_BASE +
+			       ((reg - DW_VENDOR) << 2);
+
+		return QCOM_XPCS_SR_MII_BASE + (reg << 2);
+
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+
+int xpcs_qcom_reg_read(struct platform_device *pdev, void __iomem *reg_base,
+		       int dev, int reg)
+{
+	int offset, ret;
+
+	offset = xpcs_qcom_reg_offset(dev, reg);
+	if (offset < 0)
+		return offset;
+
+	ret = pm_runtime_resume_and_get(&pdev->dev);
+	if (ret < 0)
+		return ret;
+
+	ret = readl(reg_base + offset) & 0xffff;
+
+	pm_runtime_put(&pdev->dev);
+
+	return ret;
+}
+
+int xpcs_qcom_reg_write(struct platform_device *pdev, void __iomem *reg_base,
+			int dev, int reg, u16 val)
+{
+	int offset, ret;
+
+	offset = xpcs_qcom_reg_offset(dev, reg);
+	if (offset < 0)
+		return offset;
+
+	ret = pm_runtime_resume_and_get(&pdev->dev);
+	if (ret < 0)
+		return ret;
+
+	writel(val, reg_base + offset);
+
+	pm_runtime_put(&pdev->dev);
+
+	return 0;
+}
diff --git a/drivers/net/pcs/pcs-xpcs-qcom.h b/drivers/net/pcs/pcs-xpcs-qcom.h
new file mode 100644
index 0000000000000000000000000000000000000000..a1084f6a10a96baa8ba0d192ee64cdaed90da125
--- /dev/null
+++ b/drivers/net/pcs/pcs-xpcs-qcom.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __PCS_XPCS_QCOM_H
+#define __PCS_XPCS_QCOM_H
+
+#include <linux/io.h>
+#include <linux/types.h>
+
+struct platform_device;
+
+int xpcs_qcom_reg_read(struct platform_device *pdev, void __iomem *reg_base,
+		       int dev, int reg);
+int xpcs_qcom_reg_write(struct platform_device *pdev, void __iomem *reg_base,
+			int dev, int reg, u16 val);
+
+#endif /* __PCS_XPCS_QCOM_H */
diff --git a/drivers/net/pcs/pcs-xpcs.c b/drivers/net/pcs/pcs-xpcs.c
index 7f5c7a275630f2b064e4b9abdd6c3619e9346cec..1f556b4f7c44f06f24a2f724734d3a7d71424de3 100644
--- a/drivers/net/pcs/pcs-xpcs.c
+++ b/drivers/net/pcs/pcs-xpcs.c
@@ -1571,6 +1571,15 @@ static const struct dw_xpcs_compat nxp_sja1110_xpcs_compat[] = {
 	}
 };
 
+static const struct dw_xpcs_compat qcom_nord_xpcs_compat[] = {
+	{
+		.interface = PHY_INTERFACE_MODE_USXGMII,
+		.supported = xpcs_usxgmii_features,
+		.an_mode = DW_AN_C37_USXGMII,
+	}, {
+	}
+};
+
 static const struct dw_xpcs_desc xpcs_desc_list[] = {
 	{
 		.id = DW_XPCS_ID,
@@ -1584,6 +1593,10 @@ static const struct dw_xpcs_desc xpcs_desc_list[] = {
 		.id = NXP_SJA1110_XPCS_ID,
 		.mask = DW_XPCS_ID_MASK,
 		.compat = nxp_sja1110_xpcs_compat,
+	}, {
+		.id = QCOM_NORD_XPCS_ID,
+		.mask = DW_XPCS_ID_MASK,
+		.compat = qcom_nord_xpcs_compat,
 	},
 };
 
diff --git a/include/linux/pcs/pcs-xpcs.h b/include/linux/pcs/pcs-xpcs.h
index 4ea995b70150e33e1e1a47cc7aa324c53742fbdc..0f69e14b2a4c8d17b59a570debd14a77ab040182 100644
--- a/include/linux/pcs/pcs-xpcs.h
+++ b/include/linux/pcs/pcs-xpcs.h
@@ -26,6 +26,7 @@ enum dw_xpcs_pcs_id {
 	DW_XPCS_ID_NATIVE = 0,
 	NXP_SJA1105_XPCS_ID = 0x00000010,
 	NXP_SJA1110_XPCS_ID = 0x00000020,
+	QCOM_NORD_XPCS_ID = 0x00000030,
 	DW_XPCS_ID = 0x7996ced0,
 	DW_XPCS_ID_MASK = 0xffffffff,
 };

-- 
2.34.1