linux-kernel - Re: [BUG] mmc_regulator_set_ocr can't cope with regulator-fixed

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Message-ID: <a9aa636e-326f-a848-dd69-41df87c013af@samsung.com>
Date:   Thu, 5 Aug 2021 19:00:39 +0900
From:   Jaehoon Chung <jh80.chung@...sung.com>
To:     Peter Geis <pgwipeout@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     linux-mmc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        devicetree@...r.kernel.org
Subject: Re: [BUG] mmc_regulator_set_ocr can't cope with regulator-fixed

Hi,

On 8/4/21 11:32 PM, Peter Geis wrote:
> Good Morning,
> 
> I've encountered a fun issue with the dw-mmc driver while working on
> enabling support for the Quartz-64 Model A.
> The regulator-fixed driver supports enabling via a gpio, but does not
> have the ops to set voltage as it is fixed.
> The dw-mmc calls mmc_regulator_set_ocr for vmmc, which attempts to set
> the voltage first but fails due to the lack of the voltage ops. It
> then bails returning -EINVAL.
> This leads to the following message :
> dwmmc_rockchip fe2b0000.mmc: could not set regulator OCR (-22)

What is vdd value (ocr_avail value) on your target?
I didn't see its case until now. If there is a real bug, I will try to check again.

Best Regards,
Jaehoon Chung

> 
> This can be fixed by switching to regulator-gpio for the vmmc supply
> to the sdmmc controller, however the sdio controller vmmc is provided
> by a fixed regulator that is always on. Obviously the regulator-gpio
> isn't an option, as it has no gpio to enable.
> 
> Removing the vmmc phandle from the sdio node is an option, but then it
> doesn't fully describe the hardware (it's also a non-standard 4.4v).
> I had considered changing the check in dw-mmc.c [1] to continue in the
> case of -EINVAL, but there are other places in the regulator framework
> that can also return that and it doesn't address the underlying issue.
> 
> As such I'm reaching out to the experts to see what the best course of
> action is here.
> Please weigh in with what you think.
> 
> Very Respectfully,
> Peter Geis
>