linux-kernel - [PATCH 2/4] PCI: dwc: Add helper to find the Vendor Specific Extended Capability (VSEC)

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Message-Id: <20250218-pcie-qcom-ptm-v1-2-16d7e480d73e@linaro.org>
Date: Tue, 18 Feb 2025 20:06:41 +0530
From: Manivannan Sadhasivam via B4 Relay <devnull+manivannan.sadhasivam.linaro.org@...nel.org>
To: Shuai Xue <xueshuai@...ux.alibaba.com>, 
 Jing Zhang <renyu.zj@...ux.alibaba.com>, Will Deacon <will@...nel.org>, 
 Mark Rutland <mark.rutland@....com>, Jingoo Han <jingoohan1@...il.com>, 
 Bjorn Helgaas <bhelgaas@...gle.com>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Rob Herring <robh@...nel.org>
Cc: Shradha Todi <shradha.t@...sung.com>, linux-kernel@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, linux-perf-users@...r.kernel.org, 
 linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH 2/4] PCI: dwc: Add helper to find the Vendor Specific
 Extended Capability (VSEC)

From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

dw_pcie_find_vsec_capability() is used by upcoming DWC APIs to find the
VSEC capabilities like PTM, RAS etc...

Co-developed-by: Shradha Todi <shradha.t@...sung.com>
Signed-off-by: Shradha Todi <shradha.t@...sung.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-designware.c | 40 ++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 145e7f579072..a7c0671c6715 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -16,6 +16,7 @@
 #include <linux/gpio/consumer.h>
 #include <linux/ioport.h>
 #include <linux/of.h>
+#include <linux/pcie-dwc.h>
 #include <linux/platform_device.h>
 #include <linux/sizes.h>
 #include <linux/types.h>
@@ -283,6 +284,45 @@ u16 dw_pcie_find_ext_capability(struct dw_pcie *pci, u8 cap)
 }
 EXPORT_SYMBOL_GPL(dw_pcie_find_ext_capability);
 
+static u16 __dw_pcie_find_vsec_capability(struct dw_pcie *pci, u16 vendor_id,
+					  u16 vsec_id)
+{
+	u16 vsec = 0;
+	u32 header;
+
+	if (vendor_id != dw_pcie_readw_dbi(pci, PCI_VENDOR_ID))
+		return 0;
+
+	while ((vsec = dw_pcie_find_next_ext_capability(pci, vsec,
+						       PCI_EXT_CAP_ID_VNDR))) {
+		header = dw_pcie_readl_dbi(pci, vsec + PCI_VNDR_HEADER);
+		if (PCI_VNDR_HEADER_ID(header) == vsec_id)
+			return vsec;
+	}
+
+	return 0;
+}
+
+static u16 dw_pcie_find_vsec_capability(struct dw_pcie *pci,
+					const struct dwc_pcie_vsec_id *vsec_ids)
+{
+	const struct dwc_pcie_vsec_id *vid;
+	u16 vsec;
+	u32 header;
+
+	for (vid = vsec_ids; vid->vendor_id; vid++) {
+		vsec = __dw_pcie_find_vsec_capability(pci, vid->vendor_id,
+						      vid->vsec_id);
+		if (vsec) {
+			header = dw_pcie_readl_dbi(pci, vsec + PCI_VNDR_HEADER);
+			if (PCI_VNDR_HEADER_REV(header) == vid->vsec_rev)
+				return vsec;
+		}
+	}
+
+	return 0;
+}
+
 int dw_pcie_read(void __iomem *addr, int size, u32 *val)
 {
 	if (!IS_ALIGNED((uintptr_t)addr, size)) {

-- 
2.25.1