[PATCH V2 3/7] drm/amdgpu: fix NAK-G generation during PCI-e link width switch

[Evan Quan]

A lot of NAK-G being generated when link widht switching is happening.
WA for this issue is to program the SPC to 4 symbols per clock during
bootup when the native PCIE width is x4.

Change-Id: I7a4d751e44bddc4bd1e97860cb4f53dfadc02a2c
Signed-off-by: Evan Quan <evan.quan at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/nv.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/nv.c b/drivers/gpu/drm/amd/amdgpu/nv.c
index 455d0425787c..2e1d12369cec 100644
--- a/drivers/gpu/drm/amd/amdgpu/nv.c
+++ b/drivers/gpu/drm/amd/amdgpu/nv.c
@@ -63,6 +63,10 @@
 #include "mxgpu_nv.h"
 #include "smuio_v11_0.h"
 #include "smuio_v11_0_6.h"
+#include "nbio/nbio_2_3_sh_mask.h"
+
+#define smnPCIE_LC_LINK_WIDTH_CNTL        0x11140288
+#define smnPCIE_LC_CNTL6                  0x111402ec
 
 static const struct amd_ip_funcs nv_common_ip_funcs;
 
@@ -1407,10 +1411,35 @@ static int nv_common_sw_fini(void *handle)
 	return 0;
 }
 
+static void nv_apply_lc_spc_mode_wa(struct amdgpu_device *adev)
+{
+	uint32_t reg_data = 0;
+	uint32_t link_width = 0;
+
+	reg_data = RREG32_PCIE(smnPCIE_LC_LINK_WIDTH_CNTL);
+	link_width = (reg_data & PCIE_LC_LINK_WIDTH_CNTL__LC_LINK_WIDTH_RD_MASK)
+		>> PCIE_LC_LINK_WIDTH_CNTL__LC_LINK_WIDTH_RD__SHIFT;
+
+	/*
+	 * Program PCIE_LC_CNTL6.LC_SPC_MODE_8GT to 0x2 (4 symbols per clock data)
+	 * if link_width is 0x3 (x4)
+	 */
+	if (0x3 == link_width) {
+		reg_data = RREG32_PCIE(smnPCIE_LC_CNTL6);
+		reg_data &= ~PCIE_LC_CNTL6__LC_SPC_MODE_8GT_MASK;
+		reg_data |= (0x2 << PCIE_LC_CNTL6__LC_SPC_MODE_8GT__SHIFT);
+		WREG32_PCIE(smnPCIE_LC_CNTL6, reg_data);
+	}
+}
+
 static int nv_common_hw_init(void *handle)
 {
 	struct amdgpu_device *adev = (struct amdgpu_device *)handle;
 
+	if ((adev->asic_type >= CHIP_NAVI10) &&
+	     (adev->asic_type <= CHIP_NAVI12))
+		nv_apply_lc_spc_mode_wa(adev);
+
 	/* enable pcie gen2/3 link */
 	nv_pcie_gen3_enable(adev);
 	/* enable aspm */
-- 
2.29.0