Hi Cezary,
Thank you for the review.
On Mon, Jan 10, 2022 at 3:48 PM Cezary Rojewski cezary.rojewski@intel.com 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 pavel@denx.de Signed-off-by: Lad Prabhakar prabhakar.mahadev-lad.rj@bp.renesas.com Reviewed-by: Biju Das biju.das.jz@bp.renesas.com
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