[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 <lkp at intel.com>
>> Fixes: 3100240bf846 ("drm/i915/mtl: Add hardware-level lock for steering")
>> Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan at intel.com>
>> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> 
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi at 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
>>