PCI: dwc: Add debugfs based Silicon Debug support for DWC

Add support to provide Silicon Debug interface to userspace.

This set of debug registers are part of the RAS DES feature present in
DesignWare PCIe controllers.

Co-developed-by: Manivannan Sadhasivam <[email protected]>
Signed-off-by: Shradha Todi <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Reviewed-by: Fan Ni <[email protected]>
Tested-by: Hrishikesh Deleep <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[kwilczynski: commit log, tidy up Kconfig and drop "default y", tidy up
code comments, squashed patch that fixes a NULL pointer dereference when
debugfs is already unavailable during clean-up from
https://lore.kernel.org/linux-pci/[email protected],
refactor dwc_pcie_debugfs_init() to not return errors, squashed patch that
changes how lack of the RAS DES capability is handled from
https://lore.kernel.org/linux-pci/20250304151814.6xu7cbpwpqrvcad5@thinkpad]
Signed-off-by: Krzysztof Wilczyński <[email protected]>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index a7c0671c6715..3d1d95d9e380 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -323,6 +323,12 @@ static u16 dw_pcie_find_vsec_capability(struct dw_pcie *pci,
 	return 0;
 }
 
+u16 dw_pcie_find_rasdes_capability(struct dw_pcie *pci)
+{
+	return dw_pcie_find_vsec_capability(pci, dwc_pcie_rasdes_vsec_ids);
+}
+EXPORT_SYMBOL_GPL(dw_pcie_find_rasdes_capability);
+
 int dw_pcie_read(void __iomem *addr, int size, u32 *val)
 {
 	if (!IS_ALIGNED((uintptr_t)addr, size)) {