Re: [PATCH v2] PCI: quirks: Add warm reset quirk for IBM Spyre accelerator

From: Shivaprasad G Bhat <redacted>

The IBM Spyre accelerator (PCI ID 1014:06a7) requires a dedicated warm
reset method for reliable EEH recovery on pSeries/ppc64 platforms.

FLR alone is insufficient because it does not re-initialize firmware
state machine for the current version of the card. The existing API
pci_set_pcie_reset_state() is used to drive the platform-level
PERST# using the EEH interfaces by adding a device specific quirk.

The reset function is placed in arch/powerpc/platforms/pseries/pci.c
where the EEH infrastructure is already present, declared in
pseries.h, and registered in the generic pci_dev_reset_methods[] table
in drivers/pci/quirks.c under a CONFIG_PPC_PSERIES guard.

This reset method is only registered when CONFIG_PPC_PSERIES is enabled,
so it is not available on other platforms.

Reset sequence:
  - Assert PERST# via pcie_warm_reset, hold 250 ms
  - Deassert PERST# via pcie_deassert_reset
  - Wait 250 ms for PCIe link retrain 	

Signed-off-by: Avinash Roy <redacted>
Signed-off-by: Shivaprasad G Bhat <redacted>

---
Changelog
v1: https://lore.kernel.org/linux-pci/20260805125100.1-1-avinash.roy1@linux.ibm.com/

   Reworded the commit message to highlight the warm reset requirement being
   a need of the current card and not a platform deficiency.

diff --git a/arch/powerpc/platforms/pseries/pci.c b/arch/powerpc/platforms/pseries/pci.c
index 84e4ffe957a8..7aa58d57208f 100644
--- a/arch/powerpc/platforms/pseries/pci.c
+++ b/arch/powerpc/platforms/pseries/pci.c

@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/string.h>
+#include <linux/delay.h>
 
 #include <asm/eeh.h>
 #include <asm/pci-bridge.h>

@@ -236,6 +237,41 @@ static void fixup_winbond_82c105(struct pci_dev* dev)
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_WINBOND, PCI_DEVICE_ID_WINBOND_82C105,
 			 fixup_winbond_82c105);
 
+/*
+ * Reset Spyre adapter using pci_set_pcie_reset_state()
+ * This is specifically for PPC platforms where EEH (Enhanced Error Handling)
+ * requires this reset method for proper device recovery.
+ */
+int reset_spyre(struct pci_dev *dev, bool probe)
+{
+	int ret;
+
+	if (probe)
+		return 0;
+
+	/* Assert warm reset */
+	ret = pci_set_pcie_reset_state(dev, pcie_warm_reset);
+	if (ret) {
+		pci_err(dev, "Failed to assert reset: %d\n", ret);
+		return ret;
+	}
+
+	/* Wait for reset to take effect */
+	msleep(250);

+
+	/* Deassert reset */
+	ret = pci_set_pcie_reset_state(dev, pcie_deassert_reset);
+	if (ret) {
+		pci_err(dev, "Failed to deassert reset: %d\n", ret);
+		return ret;
+	}
+
+	/* Wait for device to recover */
+	msleep(250);

+
+	return 0;
+}
+