PCI: dwc: Add helper to find the Vendor Specific Extended Capability (VSEC)

The new dw_pcie_find_vsec_capability() helper will be used within
different DWC APIs to find the VSEC capabilities like PTM, RAS, etc.

Co-developed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Shradha Todi <shradha.t@samsung.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Tested-by: Hrishikesh Deleep <hrishikesh.d@samsung.com>
Link: https://lore.kernel.org/r/20250221131548.59616-3-shradha.t@samsung.com
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 145e7f579072c94c70eef820c8f9cb6f52e5f3fe..a7c0671c6715c1b1d420d2a91606943dc2a42ba8 100644 (file)
--- 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)) {