[PATCH 2/2] drm/amd/pm: conditionally disable pcie lane/speed switching for SMU13

[Mario Limonciello]

Intel platforms such as Sapphire Rapids and Raptor Lake don't support
dynamic pcie lane or speed switching.

This limitation seems to carry over from one generation to another.
To be safer, disable dynamic pcie lane width and speed switching when
running on an Intel platform.

Link: https://edc.intel.com/content/www/us/en/design/products/platforms/details/raptor-lake-s/13th-generation-core-processors-datasheet-volume-1-of-2/005/pci-express-support/
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2663
Co-developed-by: Evan Quan <evan.quan at amd.com>
Signed-off-by: Evan Quan <evan.quan at amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
---
 .../gpu/drm/amd/pm/swsmu/smu13/smu_v13_0.c    | 42 +++++++++++++++++--
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0.c b/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0.c
index 2ef877c2cb590..cf7e729020ab6 100644
--- a/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0.c
+++ b/drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0.c
@@ -2425,6 +2425,25 @@ int smu_v13_0_mode1_reset(struct smu_context *smu)
 	return ret;
 }
 
+/*
+ * Intel hosts such as Raptor Lake and Sapphire Rapids don't support dynamic
+ * speed switching. Until we have confirmation from Intel that a specific host
+ * supports it, it's safer that we keep it disabled for all.
+ *
+ * https://edc.intel.com/content/www/us/en/design/products/platforms/details/raptor-lake-s/13th-generation-core-processors-datasheet-volume-1-of-2/005/pci-express-support/
+ * https://gitlab.freedesktop.org/drm/amd/-/issues/2663
+ */
+static bool smu_v13_0_is_pcie_dynamic_switching_supported(void)
+{
+#if IS_ENABLED(CONFIG_X86)
+	struct cpuinfo_x86 *c = &cpu_data(0);
+
+	if (c->x86_vendor == X86_VENDOR_INTEL)
+		return false;
+#endif
+	return true;
+}
+
 int smu_v13_0_update_pcie_parameters(struct smu_context *smu,
 				     uint32_t pcie_gen_cap,
 				     uint32_t pcie_width_cap)
@@ -2432,15 +2451,32 @@ int smu_v13_0_update_pcie_parameters(struct smu_context *smu,
 	struct smu_13_0_dpm_context *dpm_context = smu->smu_dpm.dpm_context;
 	struct smu_13_0_pcie_table *pcie_table =
 				&dpm_context->dpm_tables.pcie_table;
+	int num_of_levels = pcie_table->num_of_link_levels;
 	uint32_t smu_pcie_arg;
 	int ret, i;
 
-	for (i = 0; i < pcie_table->num_of_link_levels; i++) {
-		if (pcie_table->pcie_gen[i] > pcie_gen_cap)
+	if (!smu_v13_0_is_pcie_dynamic_switching_supported()) {
+		if (pcie_table->pcie_gen[num_of_levels - 1] < pcie_gen_cap)
+			pcie_gen_cap = pcie_table->pcie_gen[num_of_levels - 1];
+
+		if (pcie_table->pcie_lane[num_of_levels - 1] < pcie_width_cap)
+			pcie_width_cap = pcie_table->pcie_lane[num_of_levels - 1];
+
+		/* Force all levels to use the same settings */
+		for (i = 0; i < num_of_levels; i++) {
 			pcie_table->pcie_gen[i] = pcie_gen_cap;
-		if (pcie_table->pcie_lane[i] > pcie_width_cap)
 			pcie_table->pcie_lane[i] = pcie_width_cap;
+		}
+	} else {
+		for (i = 0; i < num_of_levels; i++) {
+			if (pcie_table->pcie_gen[i] > pcie_gen_cap)
+				pcie_table->pcie_gen[i] = pcie_gen_cap;
+			if (pcie_table->pcie_lane[i] > pcie_width_cap)
+				pcie_table->pcie_lane[i] = pcie_width_cap;
+		}
+	}
 
+	for (i = 0; i < num_of_levels; i++) {
 		smu_pcie_arg = i << 16;
 		smu_pcie_arg |= pcie_table->pcie_gen[i] << 8;
 		smu_pcie_arg |= pcie_table->pcie_lane[i];
-- 
2.25.1