diff mbox

[7/8] dmaengine: tegra20-apb-dma: Only calculate residue if txstate exists.

Message ID 5757DCAD.1090106@nvidia.com
State New
Headers show

Commit Message

Jon Hunter June 8, 2016, 8:51 a.m. UTC
Hi Peter,

On 07/06/16 18:38, Peter Griffin wrote:
> There is no point calculating the residue if there is
> no txstate to store the value.
> 
> Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
> ---
>  drivers/dma/tegra20-apb-dma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 01e316f..7f4af8c 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -814,7 +814,7 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
>  	unsigned int residual;
>  
>  	ret = dma_cookie_status(dc, cookie, txstate);
> -	if (ret == DMA_COMPLETE)
> +	if (ret == DMA_COMPLETE || !txstate)
>  		return ret;

Thanks for reporting this. I agree that we should not do this, however, 
looking at the code for Tegra, I am wondering if this could change the
actual state that is returned. Looking at dma_cookie_status() it will
call dma_async_is_complete() which will return either DMA_COMPLETE or
DMA_IN_PROGRESS. It could be possible that the actual state for the
DMA transfer in the tegra driver is DMA_ERROR, so I am wondering if we
should do something like the following  ...


Cheers
Jon

Comments

Vinod Koul June 21, 2016, 4:01 p.m. UTC | #1
On Wed, Jun 08, 2016 at 09:51:57AM +0100, Jon Hunter wrote:
> Hi Peter,
> 
> On 07/06/16 18:38, Peter Griffin wrote:
> > There is no point calculating the residue if there is
> > no txstate to store the value.
> > 
> > Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
> > ---
> >  drivers/dma/tegra20-apb-dma.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> > index 01e316f..7f4af8c 100644
> > --- a/drivers/dma/tegra20-apb-dma.c
> > +++ b/drivers/dma/tegra20-apb-dma.c
> > @@ -814,7 +814,7 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
> >  	unsigned int residual;
> >  
> >  	ret = dma_cookie_status(dc, cookie, txstate);
> > -	if (ret == DMA_COMPLETE)
> > +	if (ret == DMA_COMPLETE || !txstate)
> >  		return ret;
> 
> Thanks for reporting this. I agree that we should not do this, however, 
> looking at the code for Tegra, I am wondering if this could change the
> actual state that is returned. Looking at dma_cookie_status() it will
> call dma_async_is_complete() which will return either DMA_COMPLETE or
> DMA_IN_PROGRESS. It could be possible that the actual state for the
> DMA transfer in the tegra driver is DMA_ERROR, so I am wondering if we
> should do something like the following  ...

This one is stopping code execution when residue is not valid. Do notice
that it check for DMA_COMPLETE OR txstate. In other cases, wit will return
'that' state when txstate is NULL.

I am going to apply this.

> 
> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> index 01e316f73559..45edab7418d0 100644
> --- a/drivers/dma/tegra20-apb-dma.c
> +++ b/drivers/dma/tegra20-apb-dma.c
> @@ -822,13 +822,8 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
>         /* Check on wait_ack desc status */
>         list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) {
>                 if (dma_desc->txd.cookie == cookie) {
> -                       residual =  dma_desc->bytes_requested -
> -                                       (dma_desc->bytes_transferred %
> -                                               dma_desc->bytes_requested);
> -                       dma_set_residue(txstate, residual);
>                         ret = dma_desc->dma_status;
> -                       spin_unlock_irqrestore(&tdc->lock, flags);
> -                       return ret;
> +                       goto found;
>                 }
>         }
>  
> @@ -836,17 +831,23 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
>         list_for_each_entry(sg_req, &tdc->pending_sg_req, node) {
>                 dma_desc = sg_req->dma_desc;
>                 if (dma_desc->txd.cookie == cookie) {
> -                       residual =  dma_desc->bytes_requested -
> -                                       (dma_desc->bytes_transferred %
> -                                               dma_desc->bytes_requested);
> -                       dma_set_residue(txstate, residual);
>                         ret = dma_desc->dma_status;
> -                       spin_unlock_irqrestore(&tdc->lock, flags);
> -                       return ret;
> +                       goto found;
>                 }
>         }
>  
> -       dev_dbg(tdc2dev(tdc), "cookie %d does not found\n", cookie);
> +       dev_warn(tdc2dev(tdc), "cookie %d not found\n", cookie);
> +       spin_unlock_irqrestore(&tdc->lock, flags);
> +       return ret;
> +
> +found:
> +       if (txstate) {
> +               residual = dma_desc->bytes_requested -
> +                          (dma_desc->bytes_transferred %
> +                           dma_desc->bytes_requested);
> +               dma_set_residue(txstate, residual);
> +       }
> +

I feel this optimizes stuff, which seems okay. Feel free to send as proper
patch.

>         spin_unlock_irqrestore(&tdc->lock, flags);
>         return ret;
>  }
> 
> Cheers
> Jon
> 
> -- 
> nvpublic
Jon Hunter June 21, 2016, 5:19 p.m. UTC | #2
On 21/06/16 17:01, Vinod Koul wrote:
> On Wed, Jun 08, 2016 at 09:51:57AM +0100, Jon Hunter wrote:
>> Hi Peter,
>>
>> On 07/06/16 18:38, Peter Griffin wrote:
>>> There is no point calculating the residue if there is
>>> no txstate to store the value.
>>>
>>> Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
>>> ---
>>>  drivers/dma/tegra20-apb-dma.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
>>> index 01e316f..7f4af8c 100644
>>> --- a/drivers/dma/tegra20-apb-dma.c
>>> +++ b/drivers/dma/tegra20-apb-dma.c
>>> @@ -814,7 +814,7 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
>>>  	unsigned int residual;
>>>  
>>>  	ret = dma_cookie_status(dc, cookie, txstate);
>>> -	if (ret == DMA_COMPLETE)
>>> +	if (ret == DMA_COMPLETE || !txstate)
>>>  		return ret;
>>
>> Thanks for reporting this. I agree that we should not do this, however, 
>> looking at the code for Tegra, I am wondering if this could change the
>> actual state that is returned. Looking at dma_cookie_status() it will
>> call dma_async_is_complete() which will return either DMA_COMPLETE or
>> DMA_IN_PROGRESS. It could be possible that the actual state for the
>> DMA transfer in the tegra driver is DMA_ERROR, so I am wondering if we
>> should do something like the following  ...
> 
> This one is stopping code execution when residue is not valid. Do notice
> that it check for DMA_COMPLETE OR txstate. In other cases, wit will return
> 'that' state when txstate is NULL.

Sorry what do you mean by "this one"?

My point is that if the status is not DMA_COMPLETE, then it is possible
that it could be DMA_ERROR (for tegra that is). However,
dma_cookie_status will only return DMA_IN_PROGRESS or DMA_COMPLETE and
so if 'txstate' is NULL we will not see the DMA_ERROR status anymore and
just think it is in progress when it is actually an error.

I do agree that the driver is broken as we are not checking for
!txstate, but this also changes the behaviour a bit.

Cheers
Jon
Vinod Koul June 28, 2016, 4:04 a.m. UTC | #3
On Tue, Jun 21, 2016 at 06:19:50PM +0100, Jon Hunter wrote:
> 
> On 21/06/16 17:01, Vinod Koul wrote:
> > On Wed, Jun 08, 2016 at 09:51:57AM +0100, Jon Hunter wrote:
> >> Hi Peter,
> >>
> >> On 07/06/16 18:38, Peter Griffin wrote:
> >>> There is no point calculating the residue if there is
> >>> no txstate to store the value.
> >>>
> >>> Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
> >>> ---
> >>>  drivers/dma/tegra20-apb-dma.c | 2 +-
> >>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> >>> index 01e316f..7f4af8c 100644
> >>> --- a/drivers/dma/tegra20-apb-dma.c
> >>> +++ b/drivers/dma/tegra20-apb-dma.c
> >>> @@ -814,7 +814,7 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
> >>>  	unsigned int residual;
> >>>  
> >>>  	ret = dma_cookie_status(dc, cookie, txstate);
> >>> -	if (ret == DMA_COMPLETE)
> >>> +	if (ret == DMA_COMPLETE || !txstate)
> >>>  		return ret;
> >>
> >> Thanks for reporting this. I agree that we should not do this, however, 
> >> looking at the code for Tegra, I am wondering if this could change the
> >> actual state that is returned. Looking at dma_cookie_status() it will
> >> call dma_async_is_complete() which will return either DMA_COMPLETE or
> >> DMA_IN_PROGRESS. It could be possible that the actual state for the
> >> DMA transfer in the tegra driver is DMA_ERROR, so I am wondering if we
> >> should do something like the following  ...
> > 
> > This one is stopping code execution when residue is not valid. Do notice
> > that it check for DMA_COMPLETE OR txstate. In other cases, wit will return
> > 'that' state when txstate is NULL.
> 
> Sorry what do you mean by "this one"?

the patch

> 
> My point is that if the status is not DMA_COMPLETE, then it is possible
> that it could be DMA_ERROR (for tegra that is). 

right it can be any state... and we check for only DMA_COMPLETE as residue
has no meaning.

> However,
> dma_cookie_status will only return DMA_IN_PROGRESS or DMA_COMPLETE and
> so if 'txstate' is NULL we will not see the DMA_ERROR status anymore and
> just think it is in progress when it is actually an error.

Yes that is an existing issue, if you are reporting DMA_ERROR then you
should add a check for DMA_ERROR as well and not do residue calculation for
that case.

> 
> I do agree that the driver is broken as we are not checking for
> !txstate, but this also changes the behaviour a bit.

It changes for better and not worse. Btw pls feel free to send a patch
handling DMA_ERROR :)
diff mbox

Patch

diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index 01e316f73559..45edab7418d0 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -822,13 +822,8 @@  static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
        /* Check on wait_ack desc status */
        list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) {
                if (dma_desc->txd.cookie == cookie) {
-                       residual =  dma_desc->bytes_requested -
-                                       (dma_desc->bytes_transferred %
-                                               dma_desc->bytes_requested);
-                       dma_set_residue(txstate, residual);
                        ret = dma_desc->dma_status;
-                       spin_unlock_irqrestore(&tdc->lock, flags);
-                       return ret;
+                       goto found;
                }
        }
 
@@ -836,17 +831,23 @@  static enum dma_status tegra_dma_tx_status(struct dma_chan *dc,
        list_for_each_entry(sg_req, &tdc->pending_sg_req, node) {
                dma_desc = sg_req->dma_desc;
                if (dma_desc->txd.cookie == cookie) {
-                       residual =  dma_desc->bytes_requested -
-                                       (dma_desc->bytes_transferred %
-                                               dma_desc->bytes_requested);
-                       dma_set_residue(txstate, residual);
                        ret = dma_desc->dma_status;
-                       spin_unlock_irqrestore(&tdc->lock, flags);
-                       return ret;
+                       goto found;
                }
        }
 
-       dev_dbg(tdc2dev(tdc), "cookie %d does not found\n", cookie);
+       dev_warn(tdc2dev(tdc), "cookie %d not found\n", cookie);
+       spin_unlock_irqrestore(&tdc->lock, flags);
+       return ret;
+
+found:
+       if (txstate) {
+               residual = dma_desc->bytes_requested -
+                          (dma_desc->bytes_transferred %
+                           dma_desc->bytes_requested);
+               dma_set_residue(txstate, residual);
+       }
+
        spin_unlock_irqrestore(&tdc->lock, flags);
        return ret;
 }