linux-kernel - Re: [PATCH 1/4] [1/4] mmc: core: expose MMC_CAP2

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Date:   Fri, 21 Feb 2020 15:33:58 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Chun-Hung Wu <chun-hung.wu@...iatek.com>
Cc:     Chaotian Jing <chaotian.jing@...iatek.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Pavel Machek <pavel@....cz>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Pan Bian <bianpan2016@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Allison Randal <allison@...utok.net>,
        Mathieu Malaterre <malat@...ian.org>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Kuohong Wang <kuohong.wang@...iatek.com>,
        kernel-team@...roid.com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, wsd_upstream@...iatek.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/4] [1/4] mmc: core: expose MMC_CAP2_CQE* to dt

On Mon, Feb 17, 2020 at 7:32 AM Chun-Hung Wu <chun-hung.wu@...iatek.com> wrote:

> Expose MMC_CAP2_CQE and MMC_CAP2_CQE_DCMD
> to host->caps2 if
> 1. "supports-cqe" is defined in dt and
> 2. "disable-cqe-dcmd" is not defined in dt.
>
> ---
>  drivers/mmc/core/host.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 105b7a7..efb0dbe 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -319,6 +319,14 @@ int mmc_of_parse(struct mmc_host *host)
>                 host->caps2 |= MMC_CAP2_NO_SD;
>         if (device_property_read_bool(dev, "no-mmc"))
>                 host->caps2 |= MMC_CAP2_NO_MMC;
> +       if (device_property_read_bool(dev, "supports-cqe"))
> +               host->caps2 |= MMC_CAP2_CQE;

I don't understand why this is even a DT property as it should
be clear from the hosts compatible whether it supports CQE or
not. But it's too late to do anything about that I suppose, and
I just assume there is something I don't understand here.

> +       /* Must be after "supports-cqe" check */
> +       if (!device_property_read_bool(dev, "disable-cqe-dcmd")) {
> +               if (host->caps2 & MMC_CAP2_CQE)
> +                       host->caps2 |= MMC_CAP2_CQE_DCMD;
> +       }

This is the right place to do this I suppose. Disabling CQE
selectively is something you might wanna do for debugging.
Acked-by: Linus Walleij <linus.walleij@...aro.org>

I see that some drivers are already parsing this DT property
on their own, should we follow up with patches so that these:

$ git grep 'supports-cqe'
drivers/mmc/host/sdhci-brcmstb.c:       if
(device_property_read_bool(&pdev->dev, "supports-cqe")) {
drivers/mmc/host/sdhci-msm.c:   if (of_property_read_bool(node, "supports-cqe"))
drivers/mmc/host/sdhci-tegra.c: if
(device_property_read_bool(host->mmc->parent, "supports-cqe"))

Make use of the central parsing instead?

Yours,
Linus Walleij