On Tue, 6 Nov 2018 at 20:51, Arnd Bergmann <arnd@xxxxxxxx> wrote: > > On 11/5/18, Kishon Vijay Abraham I <kishon@xxxxxx> wrote: > > On 05/11/18 8:46 AM, Chunyan Zhang wrote: > >> > >> + sdhci_switch_extdma(host, true); > > > > A number of devices using sdhci-omap supports ADMA. So switching to > > external > > DMA shouldn't be unconditional. > > > > IMHO sdhci.c should see if the device supports ADMA or SDMA. If not it > > should > > try switching to external DMA and if external DMA too is not supported, it > > should use PIO. > > What's the reasoning for preferring ADMA/SDMA over external DMA if > both are supported? > > I'd expect that if the external DMA for some reason is worse than > ADMA, we just wouldn't list it in the DT at all, but if it's listed and > ADMA also works, then the driver should try to use it before falling > back to ADMA. Thanks Arnd and Kishon, let's see what Andrian and Ulf would suggest, and then I will address in next version of patchset. Thanks again, Chunyan > > Arnd
