linux-kernel - Re: [PATCH] mmc: sdhci-msm: Prefer asynchronous probe

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Date:   Thu, 3 Sep 2020 10:10:17 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Veerabhadrarao Badiganti <vbadigan@...eaurora.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
Subject: Re: [PATCH] mmc: sdhci-msm: Prefer asynchronous probe

On Thu, 3 Sep 2020 at 01:43, Douglas Anderson <dianders@...omium.org> wrote:
>
> Turning on initcall debug on one system showed this:
>   initcall sdhci_msm_driver_init+0x0/0x28 returned 0 after 34782 usecs
>
> The lion's share of this time (~33 ms) was in mmc_power_up().  This
> shouldn't be terribly surprising since there are a few calls to delay
> based on "power_delay_ms" and the default delay there is 10 ms.
>
> Because we haven't specified that we'd prefer asynchronous probe for
> this driver then we'll wait for this driver to finish before we start
> probes for more drivers.  While 33 ms doesn't sound like tons, every
> little bit counts.
>
> There should be little problem with turning on asynchronous probe for
> this driver.  It's already possible that previous drivers may have
> turned on asynchronous probe so we might already have other things
> (that probed before us) probing at the same time we are anyway.  This
> driver isn't really providing resources (clocks, regulators, etc) that
> other drivers need to probe and even if it was they should be handling
> -EPROBE_DEFER.
>
> Let's turn this on and get a bit of boot speed back.

Thanks for a very well written commit message!

Indeed, I am sure many mmc host drivers could benefit from a similar
change. At least regular platform drivers and amba drivers are pretty
sure to work, but who knows.

>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>

Applied for next, thanks!

Kind regards
Uffe


> ---
>
>  drivers/mmc/host/sdhci-msm.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index d4c02884cca8..9dd0dbb65382 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -2542,6 +2542,7 @@ static struct platform_driver sdhci_msm_driver = {
>                    .name = "sdhci_msm",
>                    .of_match_table = sdhci_msm_dt_match,
>                    .pm = &sdhci_msm_pm_ops,
> +                  .probe_type = PROBE_PREFER_ASYNCHRONOUS,
>         },
>  };
>
> --
> 2.28.0.402.g5ffc5be6b7-goog
>