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

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Message-ID: <CAPDyKFr2t3w1wXY+DD27vHF23mSjnUwCh7iZyuQ=ua=s+KvyVA@mail.gmail.com>
Date:   Wed, 18 Dec 2019 12:48:20 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Bao D. Nguyen" <nguyenb@...eaurora.org>
Cc:     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>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [<PATCH v1> 7/9] mmc: core: Skip frequency retries for SDCC slots

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.

Sure, I guess most of the patches can be reworked as upstreamable
solutions, but rather than looking at them all at once, please post
them separately. Additionally, in general I would appreciate more
details in the changelogs to fully understand the problems your are
solving.

Kind regards
Uffe