Re: [PATCH] drm/radeon: insist on 32-bit DMA for Cedar on PPC64/PPC64LE

Christian König <christian.koenig@xxxxxxx> · Fri, 23 Feb 2018 17:37:20 +0100



    Hi Ben,

      
      I mentioned the HD 5450 purely as a matter
        of archeological interest.

      
      Ok, in that case looking at the lspci -tv output doesn't tell us
      anything new.

      
      I suspected, but couldn't prove, that the
        problem might have something

        to do with the bridge (IBM POWER8 Host Bridge (PHB3)).

      
      In that case you would see the problem with the caicos as well.

      
      Or are there issues random enough that there could actually be
      some problem with the caicos as well and we haven't noticed it so
      far?

      
      See it is really really odd that this should only happen with the
      cedar. On the other hand if it works for now, I don't see much
      issue having this workaround.

      
      Regards,

      Christian.

      
      Am 23.02.2018 um 17:02 schrieb Ben Crocker:

    
      Hi Christian, Michel, Alex, et al.,

        
        I mentioned the HD 5450 purely as a matter of archeological
        interest.

        
        Back to the FirePro 2270 and Embedded Radeon E6465:

        
        I've attached text from both "lspci -tv" and "lspci -v."

        Actually I'm attaching a couple of different "lspci -v" outputs,
        one

        with the FirePro 2270 in place and one with the E6465 in (the
        same) place.

        
        I suspected, but couldn't prove, that the problem might have
        something

        to do with the bridge (IBM POWER8 Host Bridge (PHB3)).

        
        But I want to reiterate:

        
          Cedar GPU -> problem (before patch, that is);
          Caicos GPU in the same slot -> no problem
        
        
        -- Ben

        
        P.S.  Alex, thanks for applying the patch so expeditiously!

        
        On Fri, Feb 23, 2018 at 2:45 AM,
          Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
          wrote:

          Am 22.02.2018 um 18:56 schrieb Michel Dänzer:

              
                On 2018-02-22 06:37 PM, Ben Crocker wrote:

                
                  One of my colleagues did discover a "Radeon HG 5450
                  PCI" from February

                  2010 which did, apparently, have a Cedar GPU and very
                  definitely had a

                  (plain old) PCI connector.

                
                There must be a PCIe-to-PCI bridge on that board. The
                GPU itself is

                always PCIe, and treated accordingly by the driver.

              
            Ben, just an educated guess but is this one the one which is
            failing to work correctly?

            
            Cause the PCIe bus interface is pretty much identical over
            all generations of the last decade or so. Only the newest
            Vega10 generation is a bit different.

            
            So I strongly thing that this isn't related to the device
            being a Cedar at all, but rather that you have a bridge
            above it which doesn't correctly handle 64bit transfers.

            
            Can you please send and "lspci -t" of both the working and
            the problematic devices?

            
            Thanks,

            Christian.

          
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel