Re: [[v4] 2/5] MMC: Use CMD23 for multiblock transfers when we can.

[Andrei Warkentin <andreiw@motorola.com>]

On Fri, May 20, 2011 at 1:49 AM, Andrei Warkentin <andreiw@motorola.com> wrote:
> On Thu, May 19, 2011 at 11:38 PM, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>> Hi Andrei,
>>
>> Andrei Warkentin wrote:
>>> On Wed, May 18, 2011 at 9:37 PM, Jaehoon Chung <jh80.chung@samsung.com> wrote:
>>>> Hi Andrei
>>>>
>>>> Andrei Warkentin wrote:
>>>>> CMD23-prefixed instead of open-ended multiblock transfers
>>>>> have a performance advantage on some MMC cards.
>>>>>
>>>> you mentioned about "some MMC cards".
>>>> Conversely, that means the some card didn't have a performance advantage?
>>>>
>>>> Did you find the performance advantage?
>>>> if you found the advantage and you can tell me,
>>>> i want to know what do you have the some MMC cards..
>>>>
>>>
>>> I've tested this on a Sandisk eMMC where I saw as good as
>>> a 50% improvement on writes (30% real-life use cases). This was a
>>> SEM32G 4.3+ part.
>>
>> Can you tell me your environment? buswidth, AP information, benchmark etc..
>> And if you have the performance result's data, can you share them?
>>
>
> This was on an SDHCI controller (hence the patch...) on a Tegra
> 2-based system. I was measuring
> throughput on reads and writes (obviously without block cache,
> filesystem, etc) to an eMMC card, 8 bits.
>
> Tested both with my tool (https://github.com/andreiw/superalign) and
> an sqllite-based test.
>
> I'm attaching the data I have.
>
> A
>

Additionally, CMD23 use is a requirement for SDXC cards (Arindam can
comment on that), as well as for MMC reliable writes and eMMC 4.5-spec
features (Yunpeng Gao can comment on that).

These patches allow CMD23 use. They do involve a some changes to host
controller because of interaction with CMD12, as well as Auto-CMD12
and Auto-CMD23 features. I can definitely consult you if you need help
implementing CMD23 support for whatever controller you develop for.

A