Instead of recursively calling rz_ssi_pio_recv() use a while loop
to read the samples from RX fifo.
This also fixes an issue where the return value of rz_ssi_pio_recv()
was ignored when called recursively.
Fixes: 03e786bd4341 ("ASoC: sh: Add RZ/G2L SSIF-2 driver")
Reported-by: Pavel Machek <[email protected]>
Signed-off-by: Lad Prabhakar <[email protected]>
Reviewed-by: Biju Das <[email protected]>
---
sound/soc/sh/rz-ssi.c | 68 ++++++++++++++++++++++---------------------
1 file changed, 35 insertions(+), 33 deletions(-)
diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
index fa0cc08f70ec..37466f65c2b0 100644
--- a/sound/soc/sh/rz-ssi.c
+++ b/sound/soc/sh/rz-ssi.c
@@ -411,54 +411,56 @@ static int rz_ssi_pio_recv(struct rz_ssi_priv *ssi, struct rz_ssi_stream *strm)
{
struct snd_pcm_substream *substream = strm->substream;
struct snd_pcm_runtime *runtime;
+ bool done = false;
u16 *buf;
int fifo_samples;
int frames_left;
- int samples = 0;
+ int samples;
int i;
if (!rz_ssi_stream_is_valid(ssi, strm))
return -EINVAL;
runtime = substream->runtime;
- /* frames left in this period */
- frames_left = runtime->period_size - (strm->buffer_pos %
- runtime->period_size);
- if (frames_left == 0)
- frames_left = runtime->period_size;
- /* Samples in RX FIFO */
- fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
- SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
-
- /* Only read full frames at a time */
- while (frames_left && (fifo_samples >= runtime->channels)) {
- samples += runtime->channels;
- fifo_samples -= runtime->channels;
- frames_left--;
- }
+ while (!done) {
+ /* frames left in this period */
+ frames_left = runtime->period_size -
+ (strm->buffer_pos % runtime->period_size);
+ if (!frames_left)
+ frames_left = runtime->period_size;
+
+ /* Samples in RX FIFO */
+ fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
+ SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
+
+ /* Only read full frames at a time */
+ samples = 0;
+ while (frames_left && (fifo_samples >= runtime->channels)) {
+ samples += runtime->channels;
+ fifo_samples -= runtime->channels;
+ frames_left--;
+ }
- /* not enough samples yet */
- if (samples == 0)
- return 0;
+ /* not enough samples yet */
+ if (!samples)
+ break;
- /* calculate new buffer index */
- buf = (u16 *)(runtime->dma_area);
- buf += strm->buffer_pos * runtime->channels;
+ /* calculate new buffer index */
+ buf = (u16 *)(runtime->dma_area);
+ buf += strm->buffer_pos * runtime->channels;
- /* Note, only supports 16-bit samples */
- for (i = 0; i < samples; i++)
- *buf++ = (u16)(rz_ssi_reg_readl(ssi, SSIFRDR) >> 16);
+ /* Note, only supports 16-bit samples */
+ for (i = 0; i < samples; i++)
+ *buf++ = (u16)(rz_ssi_reg_readl(ssi, SSIFRDR) >> 16);
- rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
- rz_ssi_pointer_update(strm, samples / runtime->channels);
+ rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
+ rz_ssi_pointer_update(strm, samples / runtime->channels);
- /*
- * If we finished this period, but there are more samples in
- * the RX FIFO, call this function again
- */
- if (frames_left == 0 && fifo_samples >= runtime->channels)
- rz_ssi_pio_recv(ssi, strm);
+ /* check if there are no more samples in the RX FIFO */
+ if (!(!frames_left && fifo_samples >= runtime->channels))
+ done = true;
+ }
return 0;
}
--
2.17.1
On 2022-01-10 10:47 AM, Lad Prabhakar wrote:
> Instead of recursively calling rz_ssi_pio_recv() use a while loop
> to read the samples from RX fifo.
Recursion and loops are means for doing something repeatedly. Could you
specify _why_ such change was made i.e. the conversion from one method
into the other? I bet the code is not being changed for the sake of
changing it, the reason is simply missing in the commit message.
Please note that refactoring below function into while-loop has a side
effect: everything had to be indented by additional tab. Generally,
readability increases if function is shaped 'linearly'.
> This also fixes an issue where the return value of rz_ssi_pio_recv()
> was ignored when called recursively.
>
> Fixes: 03e786bd4341 ("ASoC: sh: Add RZ/G2L SSIF-2 driver")
> Reported-by: Pavel Machek <[email protected]>
> Signed-off-by: Lad Prabhakar <[email protected]>
> Reviewed-by: Biju Das <[email protected]>
> ---
> sound/soc/sh/rz-ssi.c | 68 ++++++++++++++++++++++---------------------
> 1 file changed, 35 insertions(+), 33 deletions(-)
>
> diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
> index fa0cc08f70ec..37466f65c2b0 100644
> --- a/sound/soc/sh/rz-ssi.c
> +++ b/sound/soc/sh/rz-ssi.c
> @@ -411,54 +411,56 @@ static int rz_ssi_pio_recv(struct rz_ssi_priv *ssi, struct rz_ssi_stream *strm)
> {
> struct snd_pcm_substream *substream = strm->substream;
> struct snd_pcm_runtime *runtime;
> + bool done = false;
> u16 *buf;
> int fifo_samples;
> int frames_left;
> - int samples = 0;
> + int samples;
> int i;
>
> if (!rz_ssi_stream_is_valid(ssi, strm))
> return -EINVAL;
>
> runtime = substream->runtime;
> - /* frames left in this period */
> - frames_left = runtime->period_size - (strm->buffer_pos %
> - runtime->period_size);
> - if (frames_left == 0)
> - frames_left = runtime->period_size;
>
> - /* Samples in RX FIFO */
> - fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
> - SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
> -
> - /* Only read full frames at a time */
> - while (frames_left && (fifo_samples >= runtime->channels)) {
> - samples += runtime->channels;
> - fifo_samples -= runtime->channels;
> - frames_left--;
> - }
> + while (!done) {
I wonder if converting this into do-while isn't a better option. Maybe
I'm missing something but 'done' flag seems to be changed only as an
outcome of the last if-statement (last step) in this entire procedure.
Perhaps condition from said if-statement could also be moved into
'while' portion of do-while loop.
> + /* frames left in this period */
> + frames_left = runtime->period_size -
> + (strm->buffer_pos % runtime->period_size);
> + if (!frames_left)
> + frames_left = runtime->period_size;
> +
> + /* Samples in RX FIFO */
> + fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
> + SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
> +
> + /* Only read full frames at a time */
> + samples = 0;
> + while (frames_left && (fifo_samples >= runtime->channels)) {
> + samples += runtime->channels;
> + fifo_samples -= runtime->channels;
> + frames_left--;
> + }
>
> - /* not enough samples yet */
> - if (samples == 0)
> - return 0;
> + /* not enough samples yet */
> + if (!samples)
> + break;
>
> - /* calculate new buffer index */
> - buf = (u16 *)(runtime->dma_area);
> - buf += strm->buffer_pos * runtime->channels;
> + /* calculate new buffer index */
> + buf = (u16 *)(runtime->dma_area);
Is the second pair of brackets needed?
> + buf += strm->buffer_pos * runtime->channels;
>
> - /* Note, only supports 16-bit samples */
> - for (i = 0; i < samples; i++)
> - *buf++ = (u16)(rz_ssi_reg_readl(ssi, SSIFRDR) >> 16);
> + /* Note, only supports 16-bit samples */
> + for (i = 0; i < samples; i++)
> + *buf++ = (u16)(rz_ssi_reg_readl(ssi, SSIFRDR) >> 16);
>
> - rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
> - rz_ssi_pointer_update(strm, samples / runtime->channels);
> + rz_ssi_reg_mask_setl(ssi, SSIFSR, SSIFSR_RDF, 0);
> + rz_ssi_pointer_update(strm, samples / runtime->channels);
>
> - /*
> - * If we finished this period, but there are more samples in
> - * the RX FIFO, call this function again
> - */
> - if (frames_left == 0 && fifo_samples >= runtime->channels)
> - rz_ssi_pio_recv(ssi, strm);
> + /* check if there are no more samples in the RX FIFO */
> + if (!(!frames_left && fifo_samples >= runtime->channels))
> + done = true;
> + }
>
> return 0;
> }
>
Hi Cezary,
Thank you for the review.
On Mon, Jan 10, 2022 at 3:48 PM Cezary Rojewski
<[email protected]> wrote:
>
> On 2022-01-10 10:47 AM, Lad Prabhakar wrote:
> > Instead of recursively calling rz_ssi_pio_recv() use a while loop
> > to read the samples from RX fifo.
>
> Recursion and loops are means for doing something repeatedly. Could you
> specify _why_ such change was made i.e. the conversion from one method
> into the other? I bet the code is not being changed for the sake of
> changing it, the reason is simply missing in the commit message.
>
I had feedback from Pavel "recursion is unwelcome in kernel due to
limited stack use." which I did agree with as a result I have come up
with this patch. Also to add this driver will later be used on Renesas
RZ/A2 SoC's which runs with limited memory.
> Please note that refactoring below function into while-loop has a side
> effect: everything had to be indented by additional tab. Generally,
> readability increases if function is shaped 'linearly'.
>
I do agree, my initial patch just added a jump back to the start of
the function if there are more samples, but Biju suggested to use a
while loop instead.
> > This also fixes an issue where the return value of rz_ssi_pio_recv()
> > was ignored when called recursively.
> >
> > Fixes: 03e786bd4341 ("ASoC: sh: Add RZ/G2L SSIF-2 driver")
> > Reported-by: Pavel Machek <[email protected]>
> > Signed-off-by: Lad Prabhakar <[email protected]>
> > Reviewed-by: Biju Das <[email protected]>
> > ---
> > sound/soc/sh/rz-ssi.c | 68 ++++++++++++++++++++++---------------------
> > 1 file changed, 35 insertions(+), 33 deletions(-)
> >
> > diff --git a/sound/soc/sh/rz-ssi.c b/sound/soc/sh/rz-ssi.c
> > index fa0cc08f70ec..37466f65c2b0 100644
> > --- a/sound/soc/sh/rz-ssi.c
> > +++ b/sound/soc/sh/rz-ssi.c
> > @@ -411,54 +411,56 @@ static int rz_ssi_pio_recv(struct rz_ssi_priv *ssi, struct rz_ssi_stream *strm)
> > {
> > struct snd_pcm_substream *substream = strm->substream;
> > struct snd_pcm_runtime *runtime;
> > + bool done = false;
> > u16 *buf;
> > int fifo_samples;
> > int frames_left;
> > - int samples = 0;
> > + int samples;
> > int i;
> >
> > if (!rz_ssi_stream_is_valid(ssi, strm))
> > return -EINVAL;
> >
> > runtime = substream->runtime;
> > - /* frames left in this period */
> > - frames_left = runtime->period_size - (strm->buffer_pos %
> > - runtime->period_size);
> > - if (frames_left == 0)
> > - frames_left = runtime->period_size;
> >
> > - /* Samples in RX FIFO */
> > - fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
> > - SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
> > -
> > - /* Only read full frames at a time */
> > - while (frames_left && (fifo_samples >= runtime->channels)) {
> > - samples += runtime->channels;
> > - fifo_samples -= runtime->channels;
> > - frames_left--;
> > - }
> > + while (!done) {
>
> I wonder if converting this into do-while isn't a better option. Maybe
> I'm missing something but 'done' flag seems to be changed only as an
> outcome of the last if-statement (last step) in this entire procedure.
> Perhaps condition from said if-statement could also be moved into
> 'while' portion of do-while loop.
>
Agreed.
> > + /* frames left in this period */
> > + frames_left = runtime->period_size -
> > + (strm->buffer_pos % runtime->period_size);
> > + if (!frames_left)
> > + frames_left = runtime->period_size;
> > +
> > + /* Samples in RX FIFO */
> > + fifo_samples = (rz_ssi_reg_readl(ssi, SSIFSR) >>
> > + SSIFSR_RDC_SHIFT) & SSIFSR_RDC_MASK;
> > +
> > + /* Only read full frames at a time */
> > + samples = 0;
> > + while (frames_left && (fifo_samples >= runtime->channels)) {
> > + samples += runtime->channels;
> > + fifo_samples -= runtime->channels;
> > + frames_left--;
> > + }
> >
> > - /* not enough samples yet */
> > - if (samples == 0)
> > - return 0;
> > + /* not enough samples yet */
> > + if (!samples)
> > + break;
> >
> > - /* calculate new buffer index */
> > - buf = (u16 *)(runtime->dma_area);
> > - buf += strm->buffer_pos * runtime->channels;
> > + /* calculate new buffer index */
> > + buf = (u16 *)(runtime->dma_area);
>
> Is the second pair of brackets needed?
>
Nope can be dropped.
Cheers,
Prabhakar
On 2022-01-10 5:03 PM, Lad, Prabhakar wrote:
> Hi Cezary,
>
> Thank you for the review.
>
...
>> Recursion and loops are means for doing something repeatedly. Could you
>> specify _why_ such change was made i.e. the conversion from one method
>> into the other? I bet the code is not being changed for the sake of
>> changing it, the reason is simply missing in the commit message.
>>
> I had feedback from Pavel "recursion is unwelcome in kernel due to
> limited stack use." which I did agree with as a result I have come up
> with this patch. Also to add this driver will later be used on Renesas
> RZ/A2 SoC's which runs with limited memory.
Adding that reasoning to the commits message will prevent questions
(such as mine) in the future. Thank you for a quick reply and a
transparent answer.
Regards,
Czarek
Hi!
> > On 2022-01-10 10:47 AM, Lad Prabhakar wrote:
> > > Instead of recursively calling rz_ssi_pio_recv() use a while loop
> > > to read the samples from RX fifo.
> >
> > Recursion and loops are means for doing something repeatedly. Could you
> > specify _why_ such change was made i.e. the conversion from one method
> > into the other? I bet the code is not being changed for the sake of
> > changing it, the reason is simply missing in the commit message.
> >
> I had feedback from Pavel "recursion is unwelcome in kernel due to
> limited stack use." which I did agree with as a result I have come up
> with this patch. Also to add this driver will later be used on Renesas
> RZ/A2 SoC's which runs with limited memory.
>
> > Please note that refactoring below function into while-loop has a side
> > effect: everything had to be indented by additional tab. Generally,
> > readability increases if function is shaped 'linearly'.
> >
> I do agree, my initial patch just added a jump back to the start of
> the function if there are more samples, but Biju suggested to use a
> while loop instead.
Yes, loop is better.
I'd actually do while(true) and avoid using the done variable.
if (!(!frames_left && fifo_samples >= runtime->channels))
break;
will do the trick. Better yet, do
if (frames_left || fifo_samples < runtime->channels)
break;
because double negation is quite confusing and looks like typo.
Best regards,
Pavel
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
On 2022-01-10 7:44 PM, Pavel Machek wrote:
> Hi!
>
>>> On 2022-01-10 10:47 AM, Lad Prabhakar wrote:
>>>> Instead of recursively calling rz_ssi_pio_recv() use a while loop
>>>> to read the samples from RX fifo.
>>>
>>> Recursion and loops are means for doing something repeatedly. Could you
>>> specify _why_ such change was made i.e. the conversion from one method
>>> into the other? I bet the code is not being changed for the sake of
>>> changing it, the reason is simply missing in the commit message.
>>>
>> I had feedback from Pavel "recursion is unwelcome in kernel due to
>> limited stack use." which I did agree with as a result I have come up
>> with this patch. Also to add this driver will later be used on Renesas
>> RZ/A2 SoC's which runs with limited memory.
...
>
> Yes, loop is better.
>
> I'd actually do while(true) and avoid using the done variable.
>
> if (!(!frames_left && fifo_samples >= runtime->channels))
> break;
>
> will do the trick. Better yet, do
>
> if (frames_left || fifo_samples < runtime->channels)
> break;
>
> because double negation is quite confusing and looks like typo.
You could achieve similar results by enlisting do-while loop. That's my
proposal.
Regards,
Czarek
On Mon, Jan 10, 2022 at 5:48 PM Cezary Rojewski
<[email protected]> wrote:
>
> On 2022-01-10 5:03 PM, Lad, Prabhakar wrote:
> > Hi Cezary,
> >
> > Thank you for the review.
> >
>
> ...
>
> >> Recursion and loops are means for doing something repeatedly. Could you
> >> specify _why_ such change was made i.e. the conversion from one method
> >> into the other? I bet the code is not being changed for the sake of
> >> changing it, the reason is simply missing in the commit message.
> >>
> > I had feedback from Pavel "recursion is unwelcome in kernel due to
> > limited stack use." which I did agree with as a result I have come up
> > with this patch. Also to add this driver will later be used on Renesas
> > RZ/A2 SoC's which runs with limited memory.
>
> Adding that reasoning to the commits message will prevent questions
> (such as mine) in the future. Thank you for a quick reply and a
> transparent answer.
>
My bad! I'll update the commit message.
CHeers,
Prabhakar