diff options
| -rw-r--r-- | drivers/gpu/drm/i915/intel_uncore.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c index 5098f95d71b0..661b50191f2b 100644 --- a/drivers/gpu/drm/i915/intel_uncore.c +++ b/drivers/gpu/drm/i915/intel_uncore.c @@ -465,6 +465,22 @@ fpga_check_for_unclaimed_mmio(struct intel_uncore *uncore) if (likely(!(dbg & FPGA_DBG_RM_NOCLAIM))) return false; + /* + * Bugs in PCI programming (or failing hardware) can occasionally cause + * us to lose access to the MMIO BAR. When this happens, register + * reads will come back with 0xFFFFFFFF for every register and things + * go bad very quickly. Let's try to detect that special case and at + * least try to print a more informative message about what has + * happened. + * + * During normal operation the FPGA_DBG register has several unused + * bits that will always read back as 0's so we can use them as canaries + * to recognize when MMIO accesses are just busted. + */ + if (unlikely(dbg == ~0)) + drm_err(&uncore->i915->drm, + "Lost access to MMIO BAR; all registers now read back as 0xFFFFFFFF!\n"); + __raw_uncore_write32(uncore, FPGA_DBG, FPGA_DBG_RM_NOCLAIM); return true; |