[RFC] mmc: dw_mmc: Fix the max_blk_count in IDMAC

[Seungwon Jeon <tgih.jun@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.jun@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;
 #else
 		mmc->max_segs = 64;
 		mmc->max_blk_size = 65536; /* BLKSIZ is 16 bits */
-- 
1.7.0.4