On 04-07-18, 13:38, Andy Shevchenko wrote: > On Wed, Jul 4, 2018 at 10:00 AM, Vinod <vkoul@xxxxxxxxxx> wrote: > > 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.. > > AFAIU serial does not need to resume. I meant the serial should check for Pause capability.. -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
