linux-kernel - Re: [PATCH] mmc: block: enable cache-flushing when mmc cache is on

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Message-ID: <7ec0cf3e316a4ed9987962b4cbf01604@hyperstone.com>
Date:   Wed, 16 Mar 2022 14:46:02 +0000
From:   Christian Löhle <CLoehle@...erstone.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Avri Altman <Avri.Altman@....com>,
        Michael Wu <michael@...winnertech.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "porzio@...il.com" <porzio@...il.com>
CC:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        allwinner-opensource-support 
        <allwinner-opensource-support@...winnertech.com>
Subject: Re: [PATCH] mmc: block: enable cache-flushing when mmc cache is on

>So we are not going to let the block layer know about SD cache?
>Or is it a separate change?

I have some code for this laying around, but as it requires reading, parsing and writing Function Registers,
in particular PEH, it's a lot of boilerplate code to get the functionality, but I'll clean it up and send a patch in the coming weeks.





From: Adrian Hunter <adrian.hunter@...el.com>
Sent: Wednesday, March 16, 2022 12:28 PM
To: Avri Altman; Michael Wu; ulf.hansson@...aro.org; beanhuo@...ron.com; porzio@...il.com
Cc: linux-mmc@...r.kernel.org; linux-kernel@...r.kernel.org; allwinner-opensource-support
Subject: Re: [PATCH] mmc: block: enable cache-flushing when mmc cache is on
    
On 16.3.2022 13.09, Avri Altman wrote:
>> Hi Avril & Adrian,
>> Thanks for your efforts. Could we have an agreement now --
>>
>> 1. enabling-cache and cmd23/reliable-write should be independent;
>>
>> Here's what I found in the spec JESD84-B51:
>>  > 6.6.31 Cache
>>  > Caching of data shall apply only for the single block
>>  > read/write(CMD17/24), pre-defined multiple block
>>  > read/write(CMD23+CMD18/25) and open ended multiple block
>>  > read/write(CMD18/25+CMD12) commands and excludes any other access
>>  > e.g., to the register space(e.g., CMD6).
>> Which means with CMD18/25+CMD12 (without using CMD23), the cache can
>> also be enabled. Maybe this could be an evidence of the independence
>> between enabling-cache and cmd23/reliable-write?
> Acked-by: Avri Altman <avri.altman@....com>
> 
> Thanks,
> Avri
> 
>>
>> 2. We don't consider supporting SD in this change.
>>
>>  > On 14/03/2022 19:10, Avri Altman wrote:
>>  >> Here is what our SD system guys wrote:
>>  >> " In SD we don’t support reliable write and this eMMC driver may not
>>  >>    be utilizing the cache feature we added in SD5.0.
>>  >>   The method of cache flush is different between SD and eMMC."
>>  >>
>>  >> So adding SD seems to be out of scope of this change.
>>
>> Is there anything else I can do about this patch? Thanks again.

So we are not going to let the block layer know about SD cache?
Or is it a separate change?
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