linux-kernel - Re: [PATCH v2] mmc: renesas_sdhi: Set the SDBUF after reset

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Message-ID: <6f1ed4ca-617e-4618-a868-44de47aa3974@tuxon.dev>
Date: Tue, 30 Apr 2024 12:27:05 +0300
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>, ulf.hansson@...aro.org,
 linux-mmc@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
 Hien Huynh <hien.huynh.px@...esas.com>
Subject: Re: [PATCH v2] mmc: renesas_sdhi: Set the SDBUF after reset

Hi, Wolfram,

On 30.04.2024 12:10, Wolfram Sang wrote:
> Hi Claudiu,
> 
> On Wed, Apr 10, 2024 at 04:54:16PM +0300, Claudiu Beznea wrote:
>> For development purpose, renesas_sdhi_probe() could be called w/
>> dma_ops = NULL to force the usage of PIO mode. In this case the
>> renesas_sdhi_enable_dma() will not be called before transferring data.
>>
>> If renesas_sdhi_enable_dma() is not called, renesas_sdhi_clk_enable()
>> call from renesas_sdhi_probe() will configure SDBUF by calling the
>> renesas_sdhi_sdbuf_width() function, but then SDBUF will be reset in
>> tmio_mmc_host_probe() when calling tmio_mmc_reset() though host->reset().
>> If SDBUF is zero the data transfer will not work in PIO mode for RZ/G3S.
>>
>> To fix this call again the renesas_sdhi_sdbuf_width(host, 16) in
>> renesas_sdhi_reset(). The call of renesas_sdhi_sdbuf_width() was not
>> removed from renesas_sdhi_clk_enable() as the host->reset() is optional.
> 
> So, I tried to find a place where we would need only one call to
> renesas_sdhi_sdbuf_width() but I also couldn't find a sweet spot. So,
> this approach seems also best to me.
> 
>> +
>> +			/*
>> +			 * In case the controller works in PIO mode the SDBUF
>> +			 * needs to be set as its reset value is zero.
>> +			 */
> 
> But I think we can shorten the above comment to something like:
> 
> 			/* Ensure default value for this driver */
>> +			renesas_sdhi_sdbuf_width(host, 16);
> 
> D'accord?

Ok! I'm going to prepare a new version to change the comment.

Thank you,
Claudiu Beznea

> 
> Happy hacking,
> 
>    Wolfram
>