linux-kernel - Re: [PATCH] mmc: mmc_spi: Add Card Detect comments and fix CD GPIO case

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Date:	Fri, 26 Feb 2016 17:50:18 +0900
From:	Magnus Damm <magnus.damm@...il.com>
To:	linux-mmc@...r.kernel.org
Cc:	Ulf Hansson <ulf.hansson@...aro.org>,
	Stephen Warren <swarren@...dia.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	adrian.hunter@...el.com, Magnus Damm <magnus.damm@...il.com>
Subject: Re: [PATCH] mmc: mmc_spi: Add Card Detect comments and fix CD GPIO case

On Tue, Feb 16, 2016 at 1:06 PM, Magnus Damm <magnus.damm@...il.com> wrote:
> From: Magnus Damm <damm+renesas@...nsource.se>
>
> This patch adds comments to describe the various ways card detection
> may be implemented and when polling is needed. Also a fix is included
> to prevent the MMC SPI driver from polling when a CD GPIO that supports
> interrupts is specified using the gpios DT property (case 1).
>
> Without this patch the DT node below results in the following output:
>
>  spi_gpio: spi-gpio { /* SD2 @ CN12 */
>          compatible = "spi-gpio";
>          #address-cells = <1>;
>          #size-cells = <0>;
>          gpio-sck = <&gpio6 16 GPIO_ACTIVE_HIGH>;
>          gpio-mosi = <&gpio6 17 GPIO_ACTIVE_HIGH>;
>          gpio-miso = <&gpio6 18 GPIO_ACTIVE_HIGH>;
>          num-chipselects = <1>;
>          cs-gpios = <&gpio6 21 GPIO_ACTIVE_LOW>;
>          status = "okay";
>
>          spi@0 {
>                  compatible = "mmc-spi-slot";
>                  reg = <0>;
>                  voltage-ranges = <3200 3400>;
>                  spi-max-frequency = <25000000>;
>                  gpios = <&gpio6 22 GPIO_ACTIVE_LOW>;   /* CD */
>          };
>  };
>
>  # dmesg | grep mmc
>  mmc_spi spi32766.0: SD/MMC host mmc0, no WP, no poweroff, cd polling
>  mmc0: host does not support reading read-only switch, assuming write-enable
>  mmc0: new SDHC card on SPI
>  mmcblk0: mmc0:0000 SU04G 3.69 GiB
>  mmcblk0: p1
>
>  With this patch applied the "cd polling" portion above disappears.
>
> Signed-off-by: Magnus Damm <damm+renesas@...nsource.se>
> ---
>
>  Developed on top of renesas-drivers-2016-02-09-v4.5-rc3 which
>  simply put is v4.5-rc3 + selected linux-next trees.
>
>  drivers/mmc/host/mmc_spi.c |   14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> --- 0001/drivers/mmc/host/mmc_spi.c
> +++ work/drivers/mmc/host/mmc_spi.c     2016-02-16 12:47:47.900513000 +0900
> @@ -1437,11 +1437,25 @@ static int mmc_spi_probe(struct spi_devi
>         if (status != 0)
>                 goto fail_add_host;
>
> +       /* Card detection in case of DT is supported in several ways:
> +        * 1) GPIO with interrupt support using "gpios" DT property.
> +        * 2) GPIO without interrupt support using "gpios" DT property.
> +        * 3) Interrupt only using "interrupt-parent/interrupts" DT properties.
> +        * 4) Both "gpios" and "interrupt-parent/interrupts" DT properties.
> +        * 5) Nothing specified.
> +        * For case 2 and 5 above polling is required.
> +        */
>         if (host->pdata && host->pdata->flags & MMC_SPI_USE_CD_GPIO) {
>                 status = mmc_gpio_request_cd(mmc, host->pdata->cd_gpio,
>                                              host->pdata->cd_debounce);
>                 if (status != 0)
>                         goto fail_add_host;
> +
> +               /* The platform has a CD GPIO signal that may support
> +                * interrupts, so let mmc_gpiod_request_cd_irq() decide
> +                * if polling is needed or not.
> +                */
> +               mmc->caps &= ~MMC_CAP_NEEDS_POLL;
>                 mmc_gpiod_request_cd_irq(mmc);
>         }
>

Did anyone run into the same issue that CD polling is enabled even
though the GPIO supports interrupt?

Perhaps it would be better to break this out into two patches - one
for the fix and one for the documentation bits?

Thanks,

/ magnus