[PATCH] mmc: rockchip_sdhci: Revert 4 blocks PIO mode read limit for RK35xx

[Jonas Karlman]

Hi Quentin,

On 2024-03-27 09:56, Quentin Schulz wrote:
> Hi Jonas,
> 
> On 3/27/24 00:35, Jonas Karlman wrote:
>> The commit 2cc6cde647e2 ("mmc: rockchip_sdhci: Limit number of blocks
>> read in a single command") introduced a limit of number of blocks to
>> read to fix a Data End Bit Error on RK3568 and RK3588. This had a side
>> affect of significant slowing down reading FIT from eMMC.
>>
>> After the commit 6de9d7b2f13c ("rockchip: rk35xx: Enable eMMC HS200 mode
>> by default") the limit of number of blocks to read workaround is no
>> longer necessary and a Data End Bit Error is no longer happening using
>> PIO mode.
>>
>> Revert this limitation to allow reading more than 4 blocks with a single
>> CMD18 command in PIO mode and speed up reading FIT from eMMC.
>>
> 
> Should we instead keep this code but surround it with
> #if !IS_ENABLED(MMC_HS200_SUPPORT)
> ?
> 
> After all, HS200 is only implied for RK35xx boards, so one could disable it.

I do not think this will be necessary, for RK3568 the PIO mode is not
needed at all and SDMA is used. And not 100% sure if it was the HS200 or
bss address change, or a combo of both that fixes the Data End Bit Error.
Or could also be that it was the DDR52 mode that caused issues.

Will re-try with normal HS mode and see if any hack is still needed at
all.

> 
> Also wondering whether we should do this dynamically based on the MMC 
> mode that could be negotiated with the chip? E.g. I think it's not 
> guaranteed that with hs200 support built and enabled in DT that it'll be 
> negotiated as HS200?

Last time I checked this there was no easy way to change number of
blocks to read at time using current mmc/sdhci ops, and I do not think
there is enough need to add new ops. However, if we still need a
workaround it should be changed to use a bounce buffer instead of limit
number of blocks to not affect performance, similar to [1].

[1] https://patchwork.ozlabs.org/patch/1895377/

Regards,
Jonas

> 
> Cheers,
> Quentin