Message-Id: <B6ECEECF-EC1D-431E-B4E4-915B29E31AEE@goldelico.com>
Date:   Wed, 10 Nov 2021 17:36:28 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Jérôme Pouiller <Jerome.Pouiller@...abs.com>,
        Avri Altman <avri.altman@....com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Tony Lindgren <tony@...mide.com>,
        Bean Huo <beanhuo@...ron.com>,
        Gražvydas Ignotas <notasas@...il.com>,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        letux-kernel@...nphoenux.org, kernel@...a-handheld.com
Subject: Re: [RFC v4 5/6] mmc: core: transplant ti,wl1251 quirks from to be
 retired omap_hsmmc

Hi Ulf,

> Am 09.11.2021 um 21:01 schrieb Ulf Hansson <ulf.hansson@...aro.org>:
> 
> On Tue, 9 Nov 2021 at 11:58, H. Nikolaus Schaller <hns@...delico.com> wrote:
>> 
>> Hi Ulf,
>> 
>>> Am 08.11.2021 um 16:33 schrieb Ulf Hansson <ulf.hansson@...aro.org>:
>>> 
>>> On Fri, 5 Nov 2021 at 10:06, H. Nikolaus Schaller <hns@...delico.com> wrote:
>>>> 
>>>> +       card->quirks |= MMC_QUIRK_NONSTD_SDIO;
>>>> +       card->cccr.wide_bus = 1;
>>>> +       card->cis.vendor = 0x104c;
>>>> +       card->cis.device = 0x9066;
>>>> +       card->cis.blksize = 512;
>>>> +       card->cis.max_dtr = 24000000;
>>>> +       card->ocr = 0x80;
>>> 
>>> In the past, we discussed a bit around why card->ocr needs to be set here.
>>> 
>>> The reason could very well be that the DTS file is specifying the
>>> vmmc-supply with 1.8V fixed regulator, which seems wrong to me.
>> 
>> I have checked with the schematics but the wlan_en regulator-fixed is just a GPIO
>> controlling some pin of the wifi chip.
>> 
>> I guess it enables some regulator or power switch inside the wifi module which
>> has unknown voltage.
>> 
>> We can interpret this as two sequential power-switches. The first one controlled
>> by the gpio-register bit and switches gpio power to the gpio pad of the SoC. The second
>> one switches the battery voltage to the internal circuits of the wifi module.
>> 
>> The GPIO itself is on 1.8V VIO level which seems to be the reason for the min/max.
>> 
>> Now it is a little arbitrary what the DTS describes: the gpio voltage or the unknown
>> internal voltage of the second switch.
>> 
>> So from hardware perspective the min/max values are irrelevant.
> 
> I completely agree with you! That's also why I earlier suggested
> moving to use an mmc-pwrseq node
> (Documentation/devicetree/bindings/mmc/mmc-pwrseq-simple.yaml), that
> would allow a better description of the HW.

Basically yes.

> Nevertheless, the important point is that the mmc core gets a valid
> host->ocr_avail to work with during card initialization. And in this
> case, it's probably good enough to model this via changing the
> regulator-min|max-microvolt to get a proper value from the
> "regulator".
> 
>> 
>>> 
>>> I would be very interested to know if we would change
>>> "regulator-min|max-microvolt" of the regulator in the DTS, into
>>> somewhere in between 2700000-3600000 (2.7-3.6V)
>> 
>> Ok, if the mmc driver does something with these values it may have indeed an influence.
>> 
>>> - and see if that
>>> allows us to drop the assignment of "card->ocr =  0x80;" above. Would
>>> you mind doing some tests for this?
>> 
>> Well, with min/max=3.3V and no ocr I get:
>> 
>> [    2.765136] omap_hsmmc 480ad000.mmc: card claims to support voltages below defined range
>> [    2.776367] omap_hsmmc 480ad000.mmc: found wl1251
>> [    2.782287] mmc2: new SDIO card at address 0001
> 
> That's really great information! During the first initialization
> attempt, things are working fine and the SDIO card gets properly
> detected.
> 
>> [   10.874237] omap_hsmmc 480ad000.mmc: could not set regulator OCR (-22)
>> [   10.945373] wl1251_sdio: probe of mmc2:0001:1 failed with error -16
> 
> It looks like the card is being re-initialized when it's time to probe
> with the SDIO func driver. This makes sense, assuming it's been
> powered off via runtime PM (the "cap-power-off-card" DT property
> should be set in the DTS for this card's slot).
> 
> I looked a bit closer to understand the problem above and then I
> realized why the card->ocr is being set from omap_hsmmc ->init_card()
> callback. It's most likely because the mmc core in
> mmc_sdio_init_card() doesn't save the card->ocr when
> MMC_QUIRK_NONSTD_SDIO is set. Instead it becomes the responsibility
> for the ->init_card() callback to do it, which seems wrong to me.
> 
> Note that the card->ocr is being used when re-initializing the SDIO card.
> 
> I have just sent a patch [1], would you mind trying it, in combination
> with not assigning card->ocr in $subject patch?

Yes, it works! I have not even played with the wlan_en regulator voltage.

> 
>> 
>> Adding back card->ocr = 0x80 (and keeping 3.3V for min/max) shows exactly the same.
>> 
>> Only min/max 1.8V + OCR works:
>> 
>> [    2.824188] mmc2: new SDIO card at address 0001
>> [    2.806518] omap_hsmmc 480ad000.mmc: card claims to support voltages below defined range
>> [    2.815979] omap_hsmmc 480ad000.mmc: found wl1251
>> [   10.981018] omap_hsmmc 480ad000.mmc: found wl1251
>> [   11.018280] wl1251: using dedicated interrupt line
>> [   11.321136] wl1251: loaded
>> [   11.378601] wl1251: initialized
>> [   14.521759] omap_hsmmc 480ad000.mmc: found wl1251
>> [   38.680725] omap_hsmmc 480ad000.mmc: found wl1251
>> [   39.646942] wl1251: 151 tx blocks at 0x3b788, 35 rx blocks at 0x3a780
>> [   39.654785] wl1251: firmware booted (Rev 4.0.4.3.7)
>> 
>> Therefore I also tried the 4th combination: min/max 1.8V and no ocr quirk and it fails again.
>> 
>> Finally I tried setting min to 2.7V and max to 3.6V. This ends up in
>> 
>> [    0.402648] reg-fixed-voltage fixed-regulator-wg7210_en: Fixed regulator specified with variable voltages
>> 
>> So it seems that we need both: min/max = 1.8V and OCR. A little unexpected since I had expected
>> that min/max is completely irrelevant.
>> 
>>> If that works, we should add some comments about it above, I think.
>> 
>> So at the moment no change for [PATCH v1] which I can now send out.
>> 
>> BR and thanks,
>> Nikolaus
>> 
> 
> Thanks a lot for doing these tests! If I am right, it looks like we
> should be able to skip assigning card->ocr for this quirk, but let's
> see.

Indeed we can. That is great.

Now the question is how to handle the dependency on your patch.
Somehow we must ensure that it is merged before my $subject patch.
Even if someone decides to backport this to stable.

BR and thanks,
Nikolaus

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