linux-kernel - Re: [PATCH V2 23/27] mmc: mmci: add variant property to request a reset

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Date:   Mon, 1 Oct 2018 11:30:44 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic Barre <ludovic.Barre@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Gerald Baeza <gerald.baeza@...com>,
        Loic Pallardy <loic.pallardy@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH V2 23/27] mmc: mmci: add variant property to request a reset

On 21 September 2018 at 11:46, Ludovic Barre <ludovic.Barre@...com> wrote:
> From: Ludovic Barre <ludovic.barre@...com>
>
> Some variants could require a reset.
> STM32 sdmmc variant needs to reset hardware block
> during the power cycle procedure (for re-initialization)
>
> Signed-off-by: Ludovic Barre <ludovic.barre@...com>
> ---
>  Documentation/devicetree/bindings/mmc/mmci.txt | 2 ++
>  drivers/mmc/host/mmci.c                        | 9 +++++++++
>  drivers/mmc/host/mmci.h                        | 4 ++++
>  3 files changed, 15 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mmc/mmci.txt b/Documentation/devicetree/bindings/mmc/mmci.txt
> index 03796cf..e952707 100644
> --- a/Documentation/devicetree/bindings/mmc/mmci.txt
> +++ b/Documentation/devicetree/bindings/mmc/mmci.txt
> @@ -11,6 +11,8 @@ Required properties:
>  - compatible             : contains "arm,pl18x", "arm,primecell".
>  - vmmc-supply            : phandle to the regulator device tree node, mentioned
>                             as the VCC/VDD supply in the eMMC/SD specs.
> +depend of variant:
> +- resets                 : phandle to internal reset line.
>

This looks like a thing depending on the SoC, rather than on the
variant. Therefore, I suggest you move this to be an optional DT
property.

Also, please move the DT doc update into a separate patch.

>  Optional properties:
>  - arm,primecell-periphid : contains the PrimeCell Peripheral ID, it overrides
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index b1d5bc5..6b3c33f 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -37,6 +37,7 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/types.h>
>  #include <linux/pinctrl/consumer.h>
> +#include <linux/reset.h>
>
>  #include <asm/div64.h>
>  #include <asm/io.h>
> @@ -1854,6 +1855,14 @@ static int mmci_probe(struct amba_device *dev,
>
>         dev_dbg(mmc_dev(mmc), "clocking block at %u Hz\n", mmc->f_max);
>
> +       if (variant->reset) {
> +               host->rst = devm_reset_control_get_exclusive(&dev->dev, NULL);

As suggested, let's make this optional and not depending on the variant.

> +               if (IS_ERR(host->rst)) {
> +                       ret = PTR_ERR(host->rst);
> +                       goto clk_disable;
> +               }
> +       }
> +
>         /* Get regulators and the supported OCR mask */
>         ret = mmc_regulator_get_supply(mmc);
>         if (ret)
> diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
> index e130689..f0fa185 100644
> --- a/drivers/mmc/host/mmci.h
> +++ b/drivers/mmc/host/mmci.h
> @@ -247,6 +247,7 @@ struct mmci_host;
>   * @start_err: bitmask identifying the STARTBITERR bit inside MMCISTATUS
>   *            register.
>   * @opendrain: bitmask identifying the OPENDRAIN bit inside MMCIPOWER register
> + * @reset: true if variant has need reset signal.
>   */
>  struct variant_data {
>         unsigned int            clkreg;
> @@ -285,6 +286,7 @@ struct variant_data {
>         bool                    qcom_dml;
>         bool                    reversed_irq_handling;
>         bool                    mmcimask1;
> +       bool                    reset;
>         unsigned int            irq_pio_mask;
>         u32                     start_err;
>         u32                     opendrain;
> @@ -318,6 +320,8 @@ struct mmci_host {
>         struct clk              *clk;
>         bool                    singleirq;
>
> +       struct reset_control    *rst;
> +
>         spinlock_t              lock;
>
>         unsigned int            mclk;
> --
> 2.7.4
>

Kind regards
Uffe