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The current radeon driver initialization routines, when using KMS, are written so that the IRQ installation routine is called before initializing the WB buffer and the CP rings. With some ASICs, though, the IRQ routine tries to access the GFX_INDEX ring causing a call to RREG32 with the value of -1 in radeon_fence_read. This, in turn causes the system to completely hang with some cards, requiring a hard reset. A call stack that can cause such a hang looks like this (using rv515 ASIC for the example here): * rv515_init (rv515.c) * radeon_irq_kms_init (radeon_irq_kms.c) * drm_irq_install (drm_irq.c) * radeon_driver_irq_preinstall_kms (radeon_irq_kms.c) * rs600_irq_process (rs600.c) * radeon_fence_process - due to SW interrupt (radeon_fence.c) * radeon_fence_read (radeon_fence.c) * hang due to RREG32(-1) The patch moves the IRQ installation to the card startup routine, after the ring has been initialized, but before the IRQ has been set. This fixes the issue, but requires a check to see if the IRQ is already installed, as is the case in the system resume codepath. I have tested the patch on three machines using the rv515, the rv770 and the evergreen ASIC. They worked without issues. This seems to be a known issue and has been reported on several bug tracking sites by various distributions (see links below). Most of reports recommend booting the system with KMS disabled and then enabling KMS by reloading the radeon module. For some reason, this was indeed a usable workaround, however, UMS is now deprecated and disabled by default. Bug reports: https://bugzilla.redhat.com/show_bug.cgi?id=845745 https://bugs.launchpad.net/ubuntu/+source/linux/+bug/561789 https://bbs.archlinux.org/viewtopic.php?id=156964 Signed-off-by: Adis Hamzić <adis@hamzadis.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Cc: stable@vger.kernel.org |
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