linux-kernel - Re: [RFC] mmc: core: transplant ti,wl1251 quirks from to be retired omap

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Date:   Wed, 27 Oct 2021 23:31:23 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Jerome Pouiller <Jerome.Pouiller@...abs.com>,
        Avri Altman <avri.altman@....com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bean Huo <beanhuo@...ron.com>, linux-mmc@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>, kernel@...a-handheld.com,
        Tony Lindgren <tony@...mide.com>,
        Linux-OMAP <linux-omap@...r.kernel.org>
Subject: Re: [RFC] mmc: core: transplant ti,wl1251 quirks from to be retired omap_hsmmc

On Wed, 27 Oct 2021 at 19:01, H. Nikolaus Schaller <hns@...delico.com> wrote:
>
> Hi Ulf,
>
> > Am 26.10.2021 um 20:08 schrieb H. Nikolaus Schaller <hns@...delico.com>:
> >
> > Hi Uf,
> >>
> >> As a matter of fact, the similar problem that you are looking to
> >> address (applying card quirks based on DT compatibility strings), is
> >> partly being taken care of in another series [1], being discussed
> >> right now. I think the solution for the ti,wl1251 should be based upon
> >> that too. Please have a look and see if you can play with that!?
> >
> > That is interesting.
> > Yes, maybe it can be the basis. At least for finding the chip and driver.
>
> I have done a first experiment.
>
> It seems as if the series [1] does the opposite of what we need... It just
> skips entries in struct mmc_fixup if the DT does *not* match.

Ohh, I didn't look that close. In that case the code isn't doing what
it *should*. The point is really to match on the compatible string and
then add quirks if that is found.

Let me have a closer look - and for sure, I am willing to help if needed.

>
> This new match is not even tried in the wl1251 case since card->cis.vendor
> and card->cis.device are not properly initialized when mmc_fixup_device() is called.
> (in the upstream code the init_card function sets these and also sets MMC_QUIRK_NONSTD_SDIO
> to early abort before sdio_read_cccr, sdio_read_common_cis, and mmc_fixup_device).

We can call mmc_fixup_device() more than once during initialization
and provide different struct mmc_fixup* - if that is needed.

>
> What I don't get from the code is how cis.vendor or cis.device can be
> initialized from device tree for a specific device. As far as I see it can
> only be checked for and some quirks can be set from a table if vendor and
> device read from the CIS registers do match.

Yes. I thought that should be possible, but maybe it is not?

>
> Instead, we want to match DT and define some values for an otherwise unknown
> device (i.e. we can't match by vendor or other methods) to help to initialize
> the interface. So in mmc_fixup_device it is too late and we need something
> running earlier, based purely on device tree information...

Okay, I will have a closer look. Maybe we need to extend the card
quirks interface a bit to make it suitable for this case too.

>
> BR and thanks,
> Nikolaus
>
>
> > [1]
> > [RFC PATCH 0/2] mmc: allow to rely on the DT to apply quirks
> > https://lore.kernel.org/lkml/20211014143031.1313783-1-Jerome.Pouiller@silabs.com/
>

Kind regards
Uffe