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

[Yuvaraj Kumar]

On Mon, Mar 24, 2014 at 9:36 AM, Jaehoon Chung <jh80.chung at samsung.com> wrote:
> Hi,
>
> Did you know that Seungwon has sent the patch "[PATCH 1/7] mmc: dw_mmc: fix the max_blk_count in IDMAC"?
> I think this patch looks like same, isn't it?
Yes.Its the same one.Please discard this patch.
> Plz check it.
>
> Best Regards,
> Jaehoon Chung
>
> On 03/24/2014 12:53 PM, Yuvaraj Kumar C D wrote:
>> From: Alim Akhtar <alim.akhtar at samsung.com>
>>
>> max_blk_count is currently set incorrectly, and the correct value can
>> be determined by looking at the maximum number of bytes which can be
>> transferred and the block size.  We use the maximum block size to
>> determine the minimum number of blocks that the controller should
>> support.  It could probably do more with a smaller block size but this
>> value should be sufficient for good performance.
>>
>> This improves sequential performance by 82% on write and 6% read on
>> one particular device.
>>
>> TEST= with this patch
>>       time dd if=/dev/zero of=/usr/local/100 bs=1M count=100 conv=fdatasync
>>       100+0 records in
>>       100+0 records out
>>       104857600 bytes (105 MB) copied, 2.62541 s, 39.9 MB/s
>>
>>       real    0m2.638s
>>       user    0m0.000s
>>       sys     0m0.645s
>>
>>       without this patch:
>>       time dd if=/dev/zero of=/usr/local/100 bs=1M count=100 conv=fdatasync
>>       100+0 records in
>>       100+0 records out
>>       104857600 bytes (105 MB) copied, 3.25873 s, 32.2 MB/s
>>
>>       real    0m3.265s
>>       user    0m0.005s
>>       sys     0m0.690s
>>
>> Signed-off-by: Seungwon Jeon <tgih.jun at samsung.com>
>> Signed-off-by: Alim Akhtar <alim.akhtar at samsung.com>
>> Signed-off-by: Sonny Rao <sonnyrao at chromium.org>
>> Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd at samsung.com>
>> ---
>>  drivers/mmc/host/dw_mmc.c |   18 ++++++++++++++++--
>>  1 file changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>> index 0c56faa..2fc4030 100644
>> --- a/drivers/mmc/host/dw_mmc.c
>> +++ b/drivers/mmc/host/dw_mmc.c
>> @@ -2213,10 +2213,24 @@ static int dw_mci_init_slot(struct dw_mci *host, unsigned int id)
>>               /* Useful defaults if platform data is unset. */
>>  #ifdef CONFIG_MMC_DW_IDMAC
>>               mmc->max_segs = host->ring_size;
>> +
>> +             /* the BLKSIZ register is 16-bits wide */
>>               mmc->max_blk_size = 65536;
>> -             mmc->max_blk_count = host->ring_size;
>> +
>> +             /*
>> +              * This value is calculated by taking the size of the
>> +              * 32-bit BYTCNT (byte count) register and dividing by the
>> +              * BLKSIZ (block size) register.  This is the minimum number
>> +              * of blocks which could be handled.
>> +              */
>> +             mmc->max_blk_count = 0xFFFF;
>>               mmc->max_seg_size = 0x1000;
>> -             mmc->max_req_size = mmc->max_seg_size * mmc->max_blk_count;
>> +             /*
>> +              * Maximum request size should be total number of descriptors
>> +              * times the maximum amount of data each can reference
>> +              */
>> +
>> +             mmc->max_req_size = mmc->max_seg_size * mmc->max_segs;
>>  #else
>>               mmc->max_segs = 64;
>>               mmc->max_blk_size = 65536; /* BLKSIZ is 16 bits */
>>
>