[PATCH] iommu/rockchip: Fix "is stall active" check

[PATCH] iommu/rockchip: Fix "is stall active" check

[John Keeping]

Since commit cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi
slaves") rk_iommu_is_stall_active() always returns false because the
bitwise AND operates on the boolean flag promoted to an integer and a
value that is either zero or BIT(2).

Explicitly convert the right-hand value to a boolean so that both sides
are guaranteed to be either zero or one.

rk_iommu_is_paging_enabled() does not suffer from the same problem since
RK_MMU_STATUS_PAGING_ENABLED is BIT(0), but let's apply the same change
for consistency and to make it clear that it's correct without needing
to lookup the value.

Fixes: cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi slaves")
Signed-off-by: John Keeping <john-HooS5bfzL4hWk0Htik3J/w@public.gmane.org>
---
 drivers/iommu/rockchip-iommu.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index a6f593a0a29e..5710a06c3049 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -315,8 +315,8 @@ static bool rk_iommu_is_stall_active(struct rk_iommu *iommu)
 	int i;
 
 	for (i = 0; i < iommu->num_mmu; i++)
-		active &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
-					RK_MMU_STATUS_STALL_ACTIVE;
+		active &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
+					   RK_MMU_STATUS_STALL_ACTIVE);
 
 	return active;
 }
@@ -327,8 +327,8 @@ static bool rk_iommu_is_paging_enabled(struct rk_iommu *iommu)
 	int i;
 
 	for (i = 0; i < iommu->num_mmu; i++)
-		enable &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
-					RK_MMU_STATUS_PAGING_ENABLED;
+		enable &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
+					   RK_MMU_STATUS_PAGING_ENABLED);
 
 	return enable;
 }
-- 
2.8.0.rc4.238.g874082a

Re: [PATCH] iommu/rockchip: Fix "is stall active" check

[Heiko Stuebner]

Am Dienstag, 5. April 2016, 15:05:46 schrieb John Keeping:
> Since commit cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi
> slaves") rk_iommu_is_stall_active() always returns false because the
> bitwise AND operates on the boolean flag promoted to an integer and a
> value that is either zero or BIT(2).
> 
> Explicitly convert the right-hand value to a boolean so that both sides
> are guaranteed to be either zero or one.
> 
> rk_iommu_is_paging_enabled() does not suffer from the same problem since
> RK_MMU_STATUS_PAGING_ENABLED is BIT(0), but let's apply the same change
> for consistency and to make it clear that it's correct without needing
> to lookup the value.
> 
> Fixes: cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi
> slaves") Signed-off-by: John Keeping <john-HooS5bfzL4hWk0Htik3J/w@public.gmane.org>

Nice catch, thanks.

Reviewed-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>

John, out of curiosity, how did you find that problem? Excess stall error 
messages or something else?


Thanks
Heiko

> ---
>  drivers/iommu/rockchip-iommu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/rockchip-iommu.c
> b/drivers/iommu/rockchip-iommu.c index a6f593a0a29e..5710a06c3049 100644
> --- a/drivers/iommu/rockchip-iommu.c
> +++ b/drivers/iommu/rockchip-iommu.c
> @@ -315,8 +315,8 @@ static bool rk_iommu_is_stall_active(struct rk_iommu
> *iommu) int i;
> 
>  	for (i = 0; i < iommu->num_mmu; i++)
> -		active &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> -					RK_MMU_STATUS_STALL_ACTIVE;
> +		active &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> +					   RK_MMU_STATUS_STALL_ACTIVE);
> 
>  	return active;
>  }
> @@ -327,8 +327,8 @@ static bool rk_iommu_is_paging_enabled(struct rk_iommu
> *iommu) int i;
> 
>  	for (i = 0; i < iommu->num_mmu; i++)
> -		enable &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> -					RK_MMU_STATUS_PAGING_ENABLED;
> +		enable &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> +					   RK_MMU_STATUS_PAGING_ENABLED);
> 
>  	return enable;
>  }

Re: [PATCH] iommu/rockchip: Fix "is stall active" check

[John Keeping]

On Tue, 05 Apr 2016 10:21:27 -0700, Heiko Stuebner wrote:

> Am Dienstag, 5. April 2016, 15:05:46 schrieb John Keeping:
> > Since commit cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi
> > slaves") rk_iommu_is_stall_active() always returns false because the
> > bitwise AND operates on the boolean flag promoted to an integer and a
> > value that is either zero or BIT(2).
> > 
> > Explicitly convert the right-hand value to a boolean so that both sides
> > are guaranteed to be either zero or one.
> > 
> > rk_iommu_is_paging_enabled() does not suffer from the same problem since
> > RK_MMU_STATUS_PAGING_ENABLED is BIT(0), but let's apply the same change
> > for consistency and to make it clear that it's correct without needing
> > to lookup the value.
> > 
> > Fixes: cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi
> > slaves") Signed-off-by: John Keeping <john-HooS5bfzL4hWk0Htik3J/w@public.gmane.org>  
> 
> Nice catch, thanks.
> 
> Reviewed-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
> 
> John, out of curiosity, how did you find that problem? Excess stall error 
> messages or something else?

I was testing the drm iommu patches I posted today [1] and noticed an
"Enable stall request timed out" error when unbinding the
display-subsystem, but the RK_MMU_STATUS value printed in the error
message indicated that stall active was set.

[1] http://article.gmane.org/gmane.comp.video.dri.devel/150721

> > ---
> >  drivers/iommu/rockchip-iommu.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/iommu/rockchip-iommu.c
> > b/drivers/iommu/rockchip-iommu.c index a6f593a0a29e..5710a06c3049 100644
> > --- a/drivers/iommu/rockchip-iommu.c
> > +++ b/drivers/iommu/rockchip-iommu.c
> > @@ -315,8 +315,8 @@ static bool rk_iommu_is_stall_active(struct rk_iommu
> > *iommu) int i;
> > 
> >  	for (i = 0; i < iommu->num_mmu; i++)
> > -		active &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > -					RK_MMU_STATUS_STALL_ACTIVE;
> > +		active &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > +					   RK_MMU_STATUS_STALL_ACTIVE);
> > 
> >  	return active;
> >  }
> > @@ -327,8 +327,8 @@ static bool rk_iommu_is_paging_enabled(struct rk_iommu
> > *iommu) int i;
> > 
> >  	for (i = 0; i < iommu->num_mmu; i++)
> > -		enable &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > -					RK_MMU_STATUS_PAGING_ENABLED;
> > +		enable &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > +					   RK_MMU_STATUS_PAGING_ENABLED);
> > 
> >  	return enable;
> >  }  
> 

Re: [PATCH] iommu/rockchip: Fix "is stall active" check

[Heiko Stuebner]

Am Dienstag, 5. April 2016, 18:28:58 schrieb John Keeping:
> On Tue, 05 Apr 2016 10:21:27 -0700, Heiko Stuebner wrote:
> > Am Dienstag, 5. April 2016, 15:05:46 schrieb John Keeping:
> > > Since commit cd6438c5f844 ("iommu/rockchip: Reconstruct to support
> > > multi
> > > slaves") rk_iommu_is_stall_active() always returns false because the
> > > bitwise AND operates on the boolean flag promoted to an integer and a
> > > value that is either zero or BIT(2).
> > > 
> > > Explicitly convert the right-hand value to a boolean so that both
> > > sides
> > > are guaranteed to be either zero or one.
> > > 
> > > rk_iommu_is_paging_enabled() does not suffer from the same problem
> > > since
> > > RK_MMU_STATUS_PAGING_ENABLED is BIT(0), but let's apply the same
> > > change
> > > for consistency and to make it clear that it's correct without needing
> > > to lookup the value.
> > > 
> > > Fixes: cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi
> > > slaves") Signed-off-by: John Keeping <john-HooS5bfzL4hWk0Htik3J/w@public.gmane.org>
> > 
> > Nice catch, thanks.
> > 
> > Reviewed-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
> > 
> > John, out of curiosity, how did you find that problem? Excess stall
> > error
> > messages or something else?
> 
> I was testing the drm iommu patches I posted today [1] and noticed an
> "Enable stall request timed out" error when unbinding the
> display-subsystem, but the RK_MMU_STATUS value printed in the error
> message indicated that stall active was set.
> 
> [1] http://article.gmane.org/gmane.comp.video.dri.devel/150721

So it seems both you and Tomeu were working to resolve the same issue [2].

And John's patch seems to actually fix the underlying problem.


[2] https://lkml.org/lkml/2016/3/22/493


> > > ---
> > > 
> > >  drivers/iommu/rockchip-iommu.c | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/iommu/rockchip-iommu.c
> > > b/drivers/iommu/rockchip-iommu.c index a6f593a0a29e..5710a06c3049
> > > 100644
> > > --- a/drivers/iommu/rockchip-iommu.c
> > > +++ b/drivers/iommu/rockchip-iommu.c
> > > @@ -315,8 +315,8 @@ static bool rk_iommu_is_stall_active(struct
> > > rk_iommu
> > > *iommu) int i;
> > > 
> > >  	for (i = 0; i < iommu->num_mmu; i++)
> > > 
> > > -		active &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > > -					RK_MMU_STATUS_STALL_ACTIVE;
> > > +		active &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > > +					   RK_MMU_STATUS_STALL_ACTIVE);
> > > 
> > >  	return active;
> > >  
> > >  }
> > > 
> > > @@ -327,8 +327,8 @@ static bool rk_iommu_is_paging_enabled(struct
> > > rk_iommu *iommu) int i;
> > > 
> > >  	for (i = 0; i < iommu->num_mmu; i++)
> > > 
> > > -		enable &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > > -					RK_MMU_STATUS_PAGING_ENABLED;
> > > +		enable &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
> > > +					   RK_MMU_STATUS_PAGING_ENABLED);
> > > 
> > >  	return enable;
> > >  
> > >  }

Re: [PATCH] iommu/rockchip: Fix "is stall active" check

[Tomeu Vizoso]

On 5 April 2016 at 21:10, Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org> wrote:
> Am Dienstag, 5. April 2016, 18:28:58 schrieb John Keeping:
>> On Tue, 05 Apr 2016 10:21:27 -0700, Heiko Stuebner wrote:
>> > Am Dienstag, 5. April 2016, 15:05:46 schrieb John Keeping:
>> > > Since commit cd6438c5f844 ("iommu/rockchip: Reconstruct to support
>> > > multi
>> > > slaves") rk_iommu_is_stall_active() always returns false because the
>> > > bitwise AND operates on the boolean flag promoted to an integer and a
>> > > value that is either zero or BIT(2).
>> > >
>> > > Explicitly convert the right-hand value to a boolean so that both
>> > > sides
>> > > are guaranteed to be either zero or one.
>> > >
>> > > rk_iommu_is_paging_enabled() does not suffer from the same problem
>> > > since
>> > > RK_MMU_STATUS_PAGING_ENABLED is BIT(0), but let's apply the same
>> > > change
>> > > for consistency and to make it clear that it's correct without needing
>> > > to lookup the value.
>> > >
>> > > Fixes: cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi
>> > > slaves") Signed-off-by: John Keeping <john-HooS5bfzL4hWk0Htik3J/w@public.gmane.org>
>> >
>> > Nice catch, thanks.
>> >
>> > Reviewed-by: Heiko Stuebner <heiko-4mtYJXux2i+zQB+pC5nmwQ@public.gmane.org>
>> >
>> > John, out of curiosity, how did you find that problem? Excess stall
>> > error
>> > messages or something else?
>>
>> I was testing the drm iommu patches I posted today [1] and noticed an
>> "Enable stall request timed out" error when unbinding the
>> display-subsystem, but the RK_MMU_STATUS value printed in the error
>> message indicated that stall active was set.
>>
>> [1] http://article.gmane.org/gmane.comp.video.dri.devel/150721
>
> So it seems both you and Tomeu were working to resolve the same issue [2].
>
> And John's patch seems to actually fix the underlying problem.

Indeed, I don't get spurious messages any more with this patch.

Tested-by: Tomeu Vizoso <tomeu.vizoso-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>

Thanks,

Tomeu

>
> [2] https://lkml.org/lkml/2016/3/22/493
>
>
>> > > ---
>> > >
>> > >  drivers/iommu/rockchip-iommu.c | 8 ++++----
>> > >  1 file changed, 4 insertions(+), 4 deletions(-)
>> > >
>> > > diff --git a/drivers/iommu/rockchip-iommu.c
>> > > b/drivers/iommu/rockchip-iommu.c index a6f593a0a29e..5710a06c3049
>> > > 100644
>> > > --- a/drivers/iommu/rockchip-iommu.c
>> > > +++ b/drivers/iommu/rockchip-iommu.c
>> > > @@ -315,8 +315,8 @@ static bool rk_iommu_is_stall_active(struct
>> > > rk_iommu
>> > > *iommu) int i;
>> > >
>> > >   for (i = 0; i < iommu->num_mmu; i++)
>> > >
>> > > -         active &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
>> > > -                                 RK_MMU_STATUS_STALL_ACTIVE;
>> > > +         active &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
>> > > +                                    RK_MMU_STATUS_STALL_ACTIVE);
>> > >
>> > >   return active;
>> > >
>> > >  }
>> > >
>> > > @@ -327,8 +327,8 @@ static bool rk_iommu_is_paging_enabled(struct
>> > > rk_iommu *iommu) int i;
>> > >
>> > >   for (i = 0; i < iommu->num_mmu; i++)
>> > >
>> > > -         enable &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
>> > > -                                 RK_MMU_STATUS_PAGING_ENABLED;
>> > > +         enable &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) &
>> > > +                                    RK_MMU_STATUS_PAGING_ENABLED);
>> > >
>> > >   return enable;
>> > >
>> > >  }
>

Re: [PATCH] iommu/rockchip: Fix "is stall active" check

[Joerg Roedel]

On Tue, Apr 05, 2016 at 03:05:46PM +0100, John Keeping wrote:
>  drivers/iommu/rockchip-iommu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)

Applied to iommu/fixes. Thanks.