Hi Marek, On 02-07-18, 15:08, Marek Szyprowski wrote: > 'cmd_pause' DMA channel capability means that respective DMA engine > supports both pausing and resuming given DMA channel. However, in some > cases it is important to know if DMA channel can be paused without the > need to resume it. This is a typical requirement for proper residue > reading on transfer timeout in UART drivers. There are also some DMA > engines with limited hardware, which doesn't really support resuming.
Am curious given that your hardware does not support resume, what was motivation for adding pause? > Reporting pause and resume capabilities separately allows UART drivers to > properly check for the really required capabilities and operate in DMA > mode also in systems with limited DMA hardware. On the other hand drivers, > which rely on full channel suspend/resume support, should now check for > both 'pause' and 'resume' features. > > Existing clients of dma_get_slave_caps() have been checked and the only > driver which rely on proper channel resuming is soc-generic-dmaengine-pcm > driver, which has been updated to check the newly added capability. > Existing 'cmd_pause' now only indicates that DMA engine support pausing > given DMA channel. The change looks fine to me. I was hoping that serial would also check this.. Mark, Lars you okay with this? > > Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com> > --- > This patch is a follow-up of the Vinod's advise from the following > discussion: > https://www.spinics.net/lists/linux-samsung-soc/msg63166.html > --- > drivers/dma/dmaengine.c | 8 ++------ > include/linux/dmaengine.h | 5 ++++- > sound/soc/soc-generic-dmaengine-pcm.c | 2 +- > 3 files changed, 7 insertions(+), 8 deletions(-) > > diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c > index 08ba8473a284..84ac38dbdb65 100644 > --- a/drivers/dma/dmaengine.c > +++ b/drivers/dma/dmaengine.c > @@ -500,12 +500,8 @@ int dma_get_slave_caps(struct dma_chan *chan, struct > dma_slave_caps *caps) > caps->max_burst = device->max_burst; > caps->residue_granularity = device->residue_granularity; > caps->descriptor_reuse = device->descriptor_reuse; > - > - /* > - * Some devices implement only pause (e.g. to get residuum) but no > - * resume. However cmd_pause is advertised as pause AND resume. > - */ > - caps->cmd_pause = !!(device->device_pause && device->device_resume); > + caps->cmd_pause = !!device->device_pause; > + caps->cmd_resume = !!device->device_resume; > caps->cmd_terminate = !!device->device_terminate_all; > > return 0; > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h > index 861be5cab1df..c8c3a7a93802 100644 > --- a/include/linux/dmaengine.h > +++ b/include/linux/dmaengine.h > @@ -415,7 +415,9 @@ enum dma_residue_granularity { > * each type, the dma controller should set BIT(<TYPE>) and same > * should be checked by controller as well > * @max_burst: max burst capability per-transfer > - * @cmd_pause: true, if pause and thereby resume is supported > + * @cmd_pause: true, if pause is supported (i.e. for reading residue or > + * for resume later) > + * @cmd_resume: true, if resume is supported > * @cmd_terminate: true, if terminate cmd is supported > * @residue_granularity: granularity of the reported transfer residue > * @descriptor_reuse: if a descriptor can be reused by client and > @@ -427,6 +429,7 @@ struct dma_slave_caps { > u32 directions; > u32 max_burst; > bool cmd_pause; > + bool cmd_resume; > bool cmd_terminate; > enum dma_residue_granularity residue_granularity; > bool descriptor_reuse; > diff --git a/sound/soc/soc-generic-dmaengine-pcm.c > b/sound/soc/soc-generic-dmaengine-pcm.c > index 56a541b9ff9e..76c46d793843 100644 > --- a/sound/soc/soc-generic-dmaengine-pcm.c > +++ b/sound/soc/soc-generic-dmaengine-pcm.c > @@ -156,7 +156,7 @@ static int dmaengine_pcm_set_runtime_hwparams(struct > snd_pcm_substream *substrea > > ret = dma_get_slave_caps(chan, &dma_caps); > if (ret == 0) { > - if (dma_caps.cmd_pause) > + if (dma_caps.cmd_pause && dma_caps.cmd_resume) > hw.info |= SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME; > if (dma_caps.residue_granularity <= > DMA_RESIDUE_GRANULARITY_SEGMENT) > hw.info |= SNDRV_PCM_INFO_BATCH; > -- > 2.17.1 > > -- > To unsubscribe from this list: send the line "unsubscribe dmaengine" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- ~Vinod
