Re: [Intel-gfx] [PATCH] drm/i915/mtl: Check full IP version when applying hw steering semaphore

[Tvrtko Ursulin]

On 02/12/2022 22:49, Rodrigo Vivi wrote:

On Fri, Dec 02, 2022 at 02:35:28PM -0800, Matt Roper wrote:

When determining whether the platform has a hardware-level steering
semaphore (i.e., MTL and beyond), we need to use GRAPHICS_VER_FULL() to
compare the full version rather than just the major version number
returned by GRAPHICS_VER().

Reported-by: kernel test robot <l...@intel.com>
Fixes: 3100240bf846 ("drm/i915/mtl: Add hardware-level lock for steering")
Cc: Balasubramani Vivekanandan <balasubramani.vivekanan...@intel.com>
Signed-off-by: Matt Roper <matthew.d.ro...@intel.com>

Reviewed-by: Rodrigo Vivi <rodrigo.v...@intel.com>

---
  drivers/gpu/drm/i915/gt/intel_gt_mcr.c | 4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c 
b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
index 087e4ac5b68d..41a237509dcf 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_mcr.c
@@ -367,7 +367,7 @@ void intel_gt_mcr_lock(struct intel_gt *gt, unsigned long 
*flags)
         * driver threads, but also with hardware/firmware agents.  A dedicated
         * locking register is used.
         */
-       if (GRAPHICS_VER(gt->i915) >= IP_VER(12, 70))
+       if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 70))

Ouch, tricky class of bugs... Anyone has an idea how to maybe coerce the 
compiler into spotting them for us, cheaply?

This one is undefined behaviour I think so not good:

-#define IP_VER(ver, rel)               ((ver) << 8 | (rel))
+typedef void * i915_full_ver_t;
+
+#define IP_VER(ver, rel) (i915_full_ver_t)(unsigned long)((ver) << 8 | (rel))

Regards,

Tvrtko

                err = wait_for(intel_uncore_read_fw(gt->uncore,
                                                    MTL_STEER_SEMAPHORE) == 
0x1, 100);

@@ -407,7 +407,7 @@ void intel_gt_mcr_unlock(struct intel_gt *gt, unsigned long flags)

  {
        spin_unlock_irqrestore(&gt->mcr_lock, flags);

- if (GRAPHICS_VER(gt->i915) >= IP_VER(12, 70))

+       if (GRAPHICS_VER_FULL(gt->i915) >= IP_VER(12, 70))
                intel_uncore_write_fw(gt->uncore, MTL_STEER_SEMAPHORE, 0x1);
  }

--

2.38.1