[PATCH] mmc: meson-gx: increase power-up delay

[Heiner Kallweit]

On 15.03.2023 16:27, Jerome Brunet wrote:
> 
> On Wed 15 Mar 2023 at 11:20, Marc Gonzalez <marc.w.gonzalez at free.fr> wrote:
> 
>> On 14/03/2023 20:45, Heiner Kallweit wrote:
>>
>>> On 14.03.2023 18:24, Marc Gonzalez wrote:
>>>
>>>> With the default power-up delay, on small kernels, the host probes
>>>> too soon, and mmc_send_io_op_cond() times out.
>>>
>>> Looking at mmc_power_up() and how power_delay_ms is used
>>> I wonder what you mean with "host probes too soon".
>>
>> Hello Heiner,
>>
>> Thanks for your interest in my patch! :)
>>
>> I should have added a link to the thread that led to the patch.
>> https://patchwork.kernel.org/project/linux-wireless/patch/c1a215cf-94be-871b-2a8a-3cc381588f83@free.fr/
>> Start at "I have run into another issue."
>>
>> Basically, I have an S905X2-based board.
>> I built a small kernel for it (with only a few drivers), that boots really fast.
>>
>> mmc2 (SDIO controller hooked to WiFi chip) would not probe at all,
>> unless I added lots of printks.
>> Basically, calling mmc_send_io_op_cond() too soon after the controller
>> has been reset leads to the CMD5 request timing out.
>>
>>
> 
> I tend to agree with Heiner here.
> This patch is backing a contraint only reported on your design in the
> driver of every AML SoC supported, for every MMC controller.
> 
> I think you should look first in your vmmc and vqmmc regulators and
> their setup times.
> 
> "fixed-regulator" have properties which might be interesting to you,
> like
>  * startup-delay-us
>  * off-on-delay-us
> 
>>> Are you sure that the additional delay is needed for the Amlogic MMC
>>> block IP in general? Or could it be that your issue is caused by
>>> a specific regulator and you need to add a delay there?
>>
>> The eternal question...
>>
>> I have only one type of board. (Actually, I have a reference design
>> that is slightly different, so I should test on that one as well.)
>>

Let me ask few more questions:

You said that the issue is with a SDIO card. How about eMMC and sdcard,
does the issue occur for them too?

Then you mention "too soon after reset", but add a delay to power-up.
If the delay would be needed after reset, then shouldn't it be in
meson_mmc_probe() after the call to device_reset_optional()?

>> In vendor kernels, they add delays to the WiFi drivers.
>> Maybe they have run into the issue, and they're just fixing the symptom?
>>
>> Default value for ios.power_delay_ms is 10 ms.
>> msleep(ios.power_delay_ms) is called twice in mmc_power_up().
>> So raising the delay from 10 to 20 adds 20 ms
>> to the latency of initializing SDIO/SD/MMC controllers.
>>
>> Would you be willing to test if the problem manifests on your board?
>>
>> Regards
>