On Thu, Feb 23, 2012 at 11:58 PM, Seungwon Jeon <tgih.jun@xxxxxxxxxxx> wrote: > Will Newton <will.newton@xxxxxxxxx> wrote: >> 2012/2/23 Seungwon Jeon <tgih.jun@xxxxxxxxxxx>: >> > Hi all, >> > >> > Even though 1MB is reserved for descriptor table in IDMAC, >> > the dw_mmc host driver is allowed to receive only maximum >> > 128KB block length in one request. This is caused by setting >> > improper max_blk_count. It needs to be e adjusted so that >> > descriptor table is used fully. >> > >> > It is found that the performance is improved with the increased the >> > max_blk_count. In my case, there is 82%(6%) improvement in sequential >> > write(read). Is there anybody who knows the reason about the old setting? >> > >> > Best regards, >> > Seungwon Jeon. >> > >> > Signed-off-by: Seungwon Jeon <tgih.jun@xxxxxxxxxxx> >> > --- >> > drivers/mmc/host/dw_mmc.c | 4 ++-- >> > 1 files changed, 2 insertions(+), 2 deletions(-) >> > >> > diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c >> > index bf3c9b4..af2b901 100644 >> > --- a/drivers/mmc/host/dw_mmc.c >> > +++ b/drivers/mmc/host/dw_mmc.c >> > @@ -1804,9 +1804,9 @@ static int __init dw_mci_init_slot(struct dw_mci *host, unsigned int id) >> > #ifdef CONFIG_MMC_DW_IDMAC >> > mmc->max_segs = host->ring_size; >> > mmc->max_blk_size = 65536; >> > - mmc->max_blk_count = host->ring_size; >> > mmc->max_seg_size = 0x1000; >> > - mmc->max_req_size = mmc->max_seg_size * mmc->max_blk_count; >> > + mmc->max_req_size = mmc->max_seg_size * host->ring_size; >> > + mmc->max_blk_count = mmc->max_req_size / 512; >> >> I am not sure this is correct, it seems like most drivers calculate >> max_req_size like this: >> >> mmc->max_req_size = mmc->max_blk_size * mmc->max_blk_count; > > Could you explain the following origin code in dw_mmc? > We need to change like most other drivers? > mmc->max_req_size = mmc->max_seg_size * mmc->max_blk_count; All the other drivers seem to set max_req_size based on blk_size and blk_count not seg_size so the current code looks like it may be wrong. > - mmc->max_blk_count is set as host->ring_size. > - max_seg_size seems to represent max_blk_size. I believe max_seg_size should be set to a higher value as it appears to be only relevant for IOMMU-based drivers, possibly the same as max_req_size. -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
