On 04/12/2013 01:38 PM, Bjorn Helgaas wrote: > On Thu, Apr 11, 2013 at 7:13 AM, Lucas Kannebley Tavares > <lucaskt at linux.vnet.ibm.com> wrote: >> radeon currently uses a drm function to get the speed capabilities for >> the bus. However, this is a non-standard method of performing this >> detection and this patch changes it to use the max_bus_speed attribute. >> --- >> drivers/gpu/drm/radeon/evergreen.c | 9 ++------- >> drivers/gpu/drm/radeon/r600.c | 8 +------- >> drivers/gpu/drm/radeon/rv770.c | 8 +------- >> 3 files changed, 4 insertions(+), 21 deletions(-) >> >> diff --git a/drivers/gpu/drm/radeon/evergreen.c >> b/drivers/gpu/drm/radeon/evergreen.c >> index 305a657..3291f62 100644 >> --- a/drivers/gpu/drm/radeon/evergreen.c >> +++ b/drivers/gpu/drm/radeon/evergreen.c >> @@ -3855,8 +3855,7 @@ void evergreen_fini(struct radeon_device *rdev) >> >> void evergreen_pcie_gen2_enable(struct radeon_device *rdev) >> { >> - u32 link_width_cntl, speed_cntl, mask; >> - int ret; >> + u32 link_width_cntl, speed_cntl; >> >> if (radeon_pcie_gen2 == 0) >> return; >> @@ -3871,11 +3870,7 @@ void evergreen_pcie_gen2_enable(struct radeon_device >> *rdev) >> if (ASIC_IS_X2(rdev)) >> return; >> >> - ret = drm_pcie_get_speed_cap_mask(rdev->ddev,&mask); >> - if (ret != 0) >> - return; >> - >> - if (!(mask& DRM_PCIE_SPEED_50)) >> + if (rdev->pdev->bus->max_bus_speed< PCIE_SPEED_5_0GT) > > For devices on a root bus, we previously dereferenced a NULL pointer > in drm_pcie_get_speed_cap_mask() because pdev->bus->self is NULL on a > root bus. (I think this is the original problem you tripped over, > Lucas.) > > These patches fix that problem. On pseries, where the device *is* on > a root bus, your patches set max_bus_speed so this will work as > expected. On most other systems, max_bus_speed for root buses will be > PCI_SPEED_UNKNOWN (set in pci_alloc_bus() and never updated because > most arches don't have code like the pseries code you're adding). > > PCI_SPEED_UNKNOWN = 0xff, so if we see another machine with a GPU on > the root bus, we'll attempt to enable Gen2 on the device even though > we have no idea what the bus will support. > > That's why I originally suggested skipping the Gen2 stuff if > "max_bus_speed == PCI_SPEED_UNKNOWN". I was just being conservative, > thinking that it's better to have a functional but slow GPU rather > than the unknown (to me) effects of enabling Gen2 on a link that might > not support it. But I'm fine with this being either way.
You're right here, of course. I'll test for it being different from 5_0GT and 8_0GT instead. Though at some point I suppose someone will want to tackle Gen3 speeds. > > It would be nice if we could get rid of drm_pcie_get_speed_cap_mask() > altogether. It is exported, but I have no idea of anybody else uses > it. Maybe it could at least be marked __deprecated now? > I'll mark it. > I don't know who should take these patches. They don't touch > drivers/pci, but I'd be happy to push them, given the appropriate ACKs > from DRM and powerpc folks. > > Bjorn > >> return; >> >> speed_cntl = RREG32_PCIE_P(PCIE_LC_SPEED_CNTL); >> diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600.c >> index 0740db3..64b90c0 100644 >> --- a/drivers/gpu/drm/radeon/r600.c >> +++ b/drivers/gpu/drm/radeon/r600.c >> @@ -4351,8 +4351,6 @@ static void r600_pcie_gen2_enable(struct radeon_device >> *rdev) >> { >> u32 link_width_cntl, lanes, speed_cntl, training_cntl, tmp; >> u16 link_cntl2; >> - u32 mask; >> - int ret; >> >> if (radeon_pcie_gen2 == 0) >> return; >> @@ -4371,11 +4369,7 @@ static void r600_pcie_gen2_enable(struct >> radeon_device *rdev) >> if (rdev->family<= CHIP_R600) >> return; >> >> - ret = drm_pcie_get_speed_cap_mask(rdev->ddev,&mask); >> - if (ret != 0) >> - return; >> - >> - if (!(mask& DRM_PCIE_SPEED_50)) >> + if (rdev->pdev->bus->max_bus_speed< PCIE_SPEED_5_0GT) >> return; >> >> speed_cntl = RREG32_PCIE_P(PCIE_LC_SPEED_CNTL); >> diff --git a/drivers/gpu/drm/radeon/rv770.c b/drivers/gpu/drm/radeon/rv770.c >> index d63fe1d..c683c36 100644 >> --- a/drivers/gpu/drm/radeon/rv770.c >> +++ b/drivers/gpu/drm/radeon/rv770.c >> @@ -1238,8 +1238,6 @@ static void rv770_pcie_gen2_enable(struct >> radeon_device *rdev) >> { >> u32 link_width_cntl, lanes, speed_cntl, tmp; >> u16 link_cntl2; >> - u32 mask; >> - int ret; >> >> if (radeon_pcie_gen2 == 0) >> return; >> @@ -1254,11 +1252,7 @@ static void rv770_pcie_gen2_enable(struct >> radeon_device *rdev) >> if (ASIC_IS_X2(rdev)) >> return; >> >> - ret = drm_pcie_get_speed_cap_mask(rdev->ddev,&mask); >> - if (ret != 0) >> - return; >> - >> - if (!(mask& DRM_PCIE_SPEED_50)) >> + if (rdev->pdev->bus->max_bus_speed< PCIE_SPEED_5_0GT) >> return; >> >> DRM_INFO("enabling PCIE gen 2 link speeds, disable with >> radeon.pcie_gen2=0\n"); >> -- >> 1.7.4.4 >> > -- Lucas Kannebley Tavares Software Engineer IBM Linux Technology Center