[PATCH] drm/panthor: flush FW AS caches in slow reset path

[Adrián Larumbe]

On 29.08.2024 15:57, Liviu Dudau wrote:
> Hi Adrián,
> 
> On Sat, Aug 17, 2024 at 11:10:17AM +0200, Boris Brezillon wrote:
> > On Fri, 16 Aug 2024 19:52:49 +0100
> > Adrián Larumbe <adrian.larumbe at collabora.com> wrote:
> > 
> > > In the off-chance that waiting for the firmware to signal its booted status
> > > timed out in the fast reset path, one must flush the cache lines for the
> > > entire FW VM address space before reloading the regions, otherwise stale
> > > values eventually lead to a scheduler job timeout.
> > > 
> > > Signed-off-by: Adrián Larumbe <adrian.larumbe at collabora.com>
> > 
> > We probably want Fixes/Cc-stable tags here.
> > 
> > > ---
> > >  drivers/gpu/drm/panthor/panthor_fw.c  |  8 +++++++-
> > >  drivers/gpu/drm/panthor/panthor_mmu.c | 19 ++++++++++++++++---
> > >  drivers/gpu/drm/panthor/panthor_mmu.h |  1 +
> > >  3 files changed, 24 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
> > > index 857f3f11258a..ef232c0c2049 100644
> > > --- a/drivers/gpu/drm/panthor/panthor_fw.c
> > > +++ b/drivers/gpu/drm/panthor/panthor_fw.c
> > > @@ -1089,6 +1089,12 @@ int panthor_fw_post_reset(struct panthor_device *ptdev)
> > >  		panthor_fw_stop(ptdev);
> > >  		ptdev->fw->fast_reset = false;
> > >  		drm_err(&ptdev->base, "FW fast reset failed, trying a slow reset");
> > > +
> > > +		ret = panthor_vm_flush_all(ptdev->fw->vm);
> > > +		if (ret) {
> > > +			drm_err(&ptdev->base, "FW slow reset failed (couldn't flush FW's AS l2cache)");
> > > +			return ret;
> > > +		}
> > >  	}
> > >  
> > >  	/* Reload all sections, including RO ones. We're not supposed
> > > @@ -1099,7 +1105,7 @@ int panthor_fw_post_reset(struct panthor_device *ptdev)
> > >  
> > >  	ret = panthor_fw_start(ptdev);
> > >  	if (ret) {
> > > -		drm_err(&ptdev->base, "FW slow reset failed");
> > > +		drm_err(&ptdev->base, "FW slow reset failed (couldn't start the FW )");
> > >  		return ret;
> > >  	}
> > >  
> > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> > > index d47972806d50..a77ee5ce691d 100644
> > > --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> > > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> > > @@ -874,14 +874,27 @@ static int panthor_vm_flush_range(struct panthor_vm *vm, u64 iova, u64 size)
> > >  	if (!drm_dev_enter(&ptdev->base, &cookie))
> > >  		return 0;
> > >  
> > > -	/* Flush the PTs only if we're already awake */
> > > -	if (pm_runtime_active(ptdev->base.dev))
> > > -		ret = mmu_hw_do_operation(vm, iova, size, AS_COMMAND_FLUSH_PT);
> > > +	/*
> > > +	 * If we made it this far, that means the device is awake, because
> > > +	 * upon device suspension, all active VMs are given an AS id of -1
> > > +	 */
> > > +	ret = mmu_hw_do_operation(vm, iova, size, AS_COMMAND_FLUSH_PT);
> > 
> > I would normally prefer this change to be in its own commit, but given
> > this is needed to be able to flush caches in the resume path, I'm fine
> > keeping it in the same patch. The comment is a bit odd now that you
> > dropped the pm_runtime_active() call though. I would rather have a
> > comment in mmu_hw_do_operation_locked(), after the AS ID check
> > explaining that as.id >= 0 guarantees that the HW is up and running,
> > and that we can proceed with the flush operation without calling
> > pm_runtime_active().
> 
> Given Boris' comments, are you planning on sending a v2?

Sure, I got caught up in a bunch of higher priority tasks this week, but I'll be
sending a v2 either before the end of this week or early next week.

> Best regards,
> Liviu
> 
> > 
> > >  
> > >  	drm_dev_exit(cookie);
> > >  	return ret;
> > >  }
> > >  
> > > +/**
> > > + * panthor_vm_flush_all() - Flush L2 caches for the entirety of a VM's AS
> > > + * @vm: VM whose cache to flush
> > > + *
> > > + * Return: 0 on success, a negative error code if flush failed.
> > > + */
> > > +int panthor_vm_flush_all(struct panthor_vm *vm)
> > > +{
> > > +	return panthor_vm_flush_range(vm, vm->base.mm_start, vm->base.mm_range);
> > > +}
> > > +
> > >  static int panthor_vm_unmap_pages(struct panthor_vm *vm, u64 iova, u64 size)
> > >  {
> > >  	struct panthor_device *ptdev = vm->ptdev;
> > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.h b/drivers/gpu/drm/panthor/panthor_mmu.h
> > > index f3c1ed19f973..6788771071e3 100644
> > > --- a/drivers/gpu/drm/panthor/panthor_mmu.h
> > > +++ b/drivers/gpu/drm/panthor/panthor_mmu.h
> > > @@ -31,6 +31,7 @@ panthor_vm_get_bo_for_va(struct panthor_vm *vm, u64 va, u64 *bo_offset);
> > >  int panthor_vm_active(struct panthor_vm *vm);
> > >  void panthor_vm_idle(struct panthor_vm *vm);
> > >  int panthor_vm_as(struct panthor_vm *vm);
> > > +int panthor_vm_flush_all(struct panthor_vm *vm);
> > >  
> > >  struct panthor_heap_pool *
> > >  panthor_vm_get_heap_pool(struct panthor_vm *vm, bool create);
> > 

Adrian Larumbe