linux-kernel - Re: [<PATCH v1> 7/9] mmc: core: Skip frequency retries for SDCC slots

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Message-ID: <CAPDyKFo929cnz9GS23B2vdDdd1RpJpYFeRwXaMFcTCEMxjS-5g@mail.gmail.com>
Date:   Wed, 18 Dec 2019 14:12:34 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "Bao D. Nguyen" <nguyenb@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Asutosh Das <asutoshd@...eaurora.org>, cang@...eaurora.org,
        Sujith Reddy Thumma <sthumma@...eaurora.org>,
        Subhash Jadavani <subhashj@...eaurora.org>,
        Xiaonian Wang <xiaonian@...eaurora.org>
Subject: Re: [<PATCH v1> 7/9] mmc: core: Skip frequency retries for SDCC slots

On Wed, 18 Dec 2019 at 13:04, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Wed, Dec 18, 2019 at 12:48:20PM +0100, Ulf Hansson wrote:
> > On Wed, 18 Dec 2019 at 09:34, Greg KH <gregkh@...uxfoundation.org> wrote:
> > >
> > > On Mon, Dec 16, 2019 at 06:50:40PM -0800, Bao D. Nguyen wrote:
> > > > From: Sujith Reddy Thumma <sthumma@...eaurora.org>
> > > >
> > > > Qualcomm SDCC controller supports minimum SD clock frequency
> > > > which is required for card initialization. This information is
> > > > exported through platform data for each SDCC controller. There is
> > > > no need of retrying higher frequencies than the minimum supported
> > > > by controller for Qualcomm chipsets which inturn add delay in
> > > > detection process if there is no card during suspend/resume cycles.
> > > > Hence, skip multiple frequency retries.
> > > >
> > > > Signed-off-by: Sujith Reddy Thumma <sthumma@...eaurora.org>
> > > > Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
> > > > Signed-off-by: Xiaonian Wang <xiaonian@...eaurora.org>
> > > > Signed-off-by: Bao D. Nguyen <nguyenb@...eaurora.org>
> > > > ---
> > > >  drivers/mmc/core/core.c | 9 +--------
> > > >  1 file changed, 1 insertion(+), 8 deletions(-)
> > > >
> > > > diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> > > > index 1e37f78..38b0cec 100644
> > > > --- a/drivers/mmc/core/core.c
> > > > +++ b/drivers/mmc/core/core.c
> > > > @@ -2281,7 +2281,6 @@ void mmc_rescan(struct work_struct *work)
> > > >  {
> > > >       struct mmc_host *host =
> > > >               container_of(work, struct mmc_host, detect.work);
> > > > -     int i;
> > > >
> > > >       if (host->rescan_disable)
> > > >               return;
> > > > @@ -2332,13 +2331,7 @@ void mmc_rescan(struct work_struct *work)
> > > >               mmc_release_host(host);
> > > >               goto out;
> > > >       }
> > > > -
> > > > -     for (i = 0; i < ARRAY_SIZE(freqs); i++) {
> > > > -             if (!mmc_rescan_try_freq(host, max(freqs[i], host->f_min)))
> > > > -                     break;
> > > > -             if (freqs[i] <= host->f_min)
> > > > -                     break;
> > > > -     }
> > > > +     mmc_rescan_try_freq(host, host->f_min);
> > >
> > > What about for non-qualcomm controllers?  Did this just break their
> > > functionality?
> >
> > Yes it does, obviously.
> >
> > Greg, thanks for providing some valuable feedback for Bao for a couple
> > of the patches in this series.
> >
> > I have also browsed through the series, but stopped providing feedback
> > after patch1, when I realized that these are all just downstream
> > vendor specific hacks.
>
> That's all kernel drivers are, vendor-specific quirks/hacks around
> broken hardware :)
>
> Splitting this out into logical fixes, like some of these are here, is
> great.  But breaking non-qualcomm hardware like this patch would do, is
> obviously not ok.
>
> > Sure, I guess most of the patches can be reworked as upstreamable
> > solutions,
>
> They have to be upstreamable, you don't want these in random vendor
> trees as they go no where and atrophy and break users.  We want them in
> our main tree for everyone to use for the obvious reason that they are
> needed to get real hardware working.

I fully agree and I am willing to help!

Just didn't want to waste my time reviewing all at once in great
detail - if it turns out that the submitter don't care to re-spin, as
that has happened before (not by Bao).

Kind regards
Uffe