Will Newton <will.new...@gmail.com> wrote: > 2012/2/23 Seungwon Jeon <tgih....@samsung.com>: > > 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....@samsung.com> > > --- > > 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; - mmc->max_blk_count is set as host->ring_size. - max_seg_size seems to represent max_blk_size. I think max_req_size means the total transfer size through DMA descriptors. max_blk_size just is limited to 16 bits for BLKSIZ register. Actually 512 is used. Host driver doesn't inform block layer of this size. Also, block layer doesn't utilize max_blk_size. Thanks, Seungwon Jeon. > > And indeed in the external DMA case dw_mmc does that too. > > It should probably be safe to set max_seg_size to max_req_size too. > > > #else > > mmc->max_segs = 64; > > mmc->max_blk_size = 65536; /* BLKSIZ is 16 bits */ > > -- > > 1.7.0.4 > > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > > the body of a message to majord...@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
