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authorPaul Parsons <lost.distance@yahoo.com>2016-04-02 12:32:30 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-04-24 09:34:16 +0200
commit9607290a18352cba4a7d015d826c1ce40bdb25bb (patch)
treed04ae14f4ab49b579539f9870c8debcf21041650
parent7c320edaa4c8b5c864b11c5e5c51b9dfd36a19c4 (diff)
drm/radeon: Fix PCIe lane width calculation
commit 85e290d92b4b794d0c758c53007eb4248d385386 upstream. Two years ago I tried an AMD Radeon E8860 embedded GPU with the drm driver. The dmesg output included driver warnings about an invalid PCIe lane width. Tracking the problem back led to si_set_pcie_lane_width_in_smc(). The calculation of the lane widths via ATOM_PPLIB_PCIE_LINK_WIDTH_MASK and ATOM_PPLIB_PCIE_LINK_WIDTH_SHIFT macros did not increment the resulting value, per the comment in pptable.h ("lanes - 1"), and per usage elsewhere. Applying the increment silenced the warnings. The code has not changed since, so either my analysis was incorrect or the bug has gone unnoticed. Hence submitting this as an RFC. Acked-by: Christian K├Ânig <christian.koenig@amd.com> Acked-by: Chunming Zhou <david1.zhou@amd.com> Signed-off-by: Paul Parsons <lost.distance@yahoo.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/gpu/drm/radeon/si_dpm.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/gpu/drm/radeon/si_dpm.c b/drivers/gpu/drm/radeon/si_dpm.c
index 574ab0016a57..b82ef5ed727c 100644
--- a/drivers/gpu/drm/radeon/si_dpm.c
+++ b/drivers/gpu/drm/radeon/si_dpm.c
@@ -5969,9 +5969,9 @@ static void si_set_pcie_lane_width_in_smc(struct radeon_device *rdev,
{
u32 lane_width;
u32 new_lane_width =
- (radeon_new_state->caps & ATOM_PPLIB_PCIE_LINK_WIDTH_MASK) >> ATOM_PPLIB_PCIE_LINK_WIDTH_SHIFT;
+ ((radeon_new_state->caps & ATOM_PPLIB_PCIE_LINK_WIDTH_MASK) >> ATOM_PPLIB_PCIE_LINK_WIDTH_SHIFT) + 1;
u32 current_lane_width =
- (radeon_current_state->caps & ATOM_PPLIB_PCIE_LINK_WIDTH_MASK) >> ATOM_PPLIB_PCIE_LINK_WIDTH_SHIFT;
+ ((radeon_current_state->caps & ATOM_PPLIB_PCIE_LINK_WIDTH_MASK) >> ATOM_PPLIB_PCIE_LINK_WIDTH_SHIFT) + 1;
if (new_lane_width != current_lane_width) {
radeon_set_pcie_lanes(rdev, new_lane_width);