linux-kernel - Re: [PATCH v4] mmc: mxs-mmc: Introduce regulator support

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Date:   Mon, 28 Jan 2019 22:15:23 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Martin Kepplinger <martink@...teo.de>
Cc:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Robin van der Gracht <robin@...tonic.nl>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Martin Kepplinger <martin.kepplinger@...zinger.com>
Subject: Re: [PATCH v4] mmc: mxs-mmc: Introduce regulator support

On Mon, 28 Jan 2019 at 15:41, Martin Kepplinger <martink@...teo.de> wrote:
>
> From: Martin Kepplinger <martin.kepplinger@...zinger.com>
>
> This adds support for explicitly switching the mmc's power on and off
> which is needed for example for WL1837 WL1271 wifi controllers on imx28.
>
> While the wifi's vmmc-supply regulator can be configured in devicetree,
> "ip link set wlan0 down" doesn't turn off the VMMC regulator which leads
> to hangs when loading firmware, for example.
>
> Signed-off-by: Martin Kepplinger <martin.kepplinger@...zinger.com>
> ---
>
>
> revision history
> ----------------
> v4: re-added forgotten regulator_enable() during probe
> v3: improve API usage as suggested by Ulf
> v2: tested patch with changes suggested by Robin
> v1: question, why https://patchwork.kernel.org/patch/4365751/ didn't get in
>
>
>  drivers/mmc/host/mxs-mmc.c | 34 +++++++++++++++++++++++++---------
>  1 file changed, 25 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/mmc/host/mxs-mmc.c b/drivers/mmc/host/mxs-mmc.c
> index add1e70195ea..23d275269d61 100644
> --- a/drivers/mmc/host/mxs-mmc.c
> +++ b/drivers/mmc/host/mxs-mmc.c
> @@ -517,6 +517,22 @@ static void mxs_mmc_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>         else
>                 host->bus_width = 0;
>
> +       switch (ios->power_mode) {
> +       case MMC_POWER_OFF:
> +               if (!IS_ERR(host->mmc->supply.vmmc))
> +                       mmc_regulator_set_ocr(host->mmc,
> +                                             host->mmc->supply.vmmc, 0);
> +               break;
> +       case MMC_POWER_UP:
> +               if (!IS_ERR(host->mmc->supply.vmmc))
> +                       mmc_regulator_set_ocr(host->mmc,
> +                                             host->mmc->supply.vmmc,
> +                                             ios->vdd);
> +               break;
> +       default:
> +               break;
> +       }
> +
>         if (ios->clock)
>                 mxs_ssp_set_clk_rate(&host->ssp, ios->clock);
>  }
> @@ -588,7 +604,6 @@ static int mxs_mmc_probe(struct platform_device *pdev)
>         struct mmc_host *mmc;
>         struct resource *iores;
>         int ret = 0, irq_err;
> -       struct regulator *reg_vmmc;
>         struct mxs_ssp *ssp;
>
>         irq_err = platform_get_irq(pdev, 0);
> @@ -614,14 +629,15 @@ static int mxs_mmc_probe(struct platform_device *pdev)
>         host->mmc = mmc;
>         host->sdio_irq_en = 0;
>
> -       reg_vmmc = devm_regulator_get(&pdev->dev, "vmmc");
> -       if (!IS_ERR(reg_vmmc)) {
> -               ret = regulator_enable(reg_vmmc);
> -               if (ret) {
> -                       dev_err(&pdev->dev,
> -                               "Failed to enable vmmc regulator: %d\n", ret);
> -                       goto out_mmc_free;
> -               }
> +       ret = mmc_regulator_get_supply(mmc);
> +       if (ret == -EPROBE_DEFER)
> +               goto out_mmc_free;
> +
> +       ret = regulator_enable(mmc->supply.vmmc);

This is wrong, as it may cause the regulator usage count to become
wrongly balanced.

Instead, via ->set_ios() when calling mmc_regulator_set_ocr(), it will
take care of enabling and disabling the regulator depending of the
requested vdd voltage level.

> +       if (ret) {
> +               dev_err(&pdev->dev,
> +                       "Failed to enable vmmc regulator: %d\n", ret);
> +               goto out_mmc_free;
>         }
>
>         ssp->clk = devm_clk_get(&pdev->dev, NULL);
> --
> 2.20.1
>

BTW, you didn't really answer my earlier question about the TI WiFi
chip. Doesn't you need a special clock for WiFi chip as well? How do
you intend to manage that?

Kind regards
Uffe