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. -- With Best Regards, Andy Shevchenko -- 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
