From 85e290d92b4b794d0c758c53007eb4248d385386 Mon Sep 17 00:00:00 2001 From: Paul Parsons Date: Sat, 2 Apr 2016 12:32:30 +0100 Subject: [PATCH] drm/radeon: Fix PCIe lane width calculation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 König Acked-by: Chunming Zhou Signed-off-by: Paul Parsons Signed-off-by: Alex Deucher Cc: stable@vger.kernel.org --- drivers/gpu/drm/radeon/si_dpm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/radeon/si_dpm.c b/drivers/gpu/drm/radeon/si_dpm.c index 97a0a639dad9..90d5b41007bf 100644 --- a/drivers/gpu/drm/radeon/si_dpm.c +++ b/drivers/gpu/drm/radeon/si_dpm.c @@ -5912,9 +5912,9 @@ 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); -- 2.30.2