> On November 22, 2019 at 7:13 AM Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote: > > > This patch can improve performance when a sd card transfer size > is multiples of 32 like a sd memory card. However, this may > disimprove performance when a sd card transfer size is not > multiples of 32 because this patch uses PIO instead of SYS-DMAC. I have logged the DMA transfer sizes of a Marvell SD8897 WiFi/BT chip, and there transfers that are not multiples of 32 are infrequent (every second or so) and small (184 bytes); all large transfers are multiples of 32. Would it be practical to switch the DMA bus width down if odd sizes are encountered, and back up again otherwise? CU Uli
