linux-kernel - Re: [PATCH] sdhci: Add quirk and device tree parameter to force SD test mode

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Date:   Mon, 22 Aug 2016 19:46:09 -0700
From:   Frank Rowand <frowand.list@...il.com>
To:     Zach Brown <zach.brown@...com>, adrian.hunter@...el.com
Cc:     ulf.hansson@...aro.org, mark.rutland@....com, robh+dt@...nel.org,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sdhci: Add quirk and device tree parameter to force SD
 test mode

On 08/22/16 15:55, Zach Brown wrote:
> From: Jaeden Amero <jaeden.amero@...com>
> 
> On some devices, CD is broken so that we must force the SDHCI into test
> mode and set CD, so that it always detects an SD card as present.
> 
> In order to get a device with broken CD working, we had previously
> always set the SDHCI into test mode. Unfortunately, this had the side
> effect of making all SD cards used with our Linux kernels undetectable
> and non-removable.
> 
> By making this "SD test mode" setting optional via a quirk, we can avoid
> this side effect for devices other than the device with broken CD.
> Additionally, we add a device parameter to sdhci-pltfm to allow all
> SDHCI drivers to enable this quirk.
> 
> Signed-off-by: Jaeden Amero <jaeden.amero@...com>
> Signed-off-by: Zach Brown <zach.brown@...com>
> ---
>  Documentation/devicetree/bindings/mmc/mmc.txt | 2 ++
>  drivers/mmc/host/sdhci-pltfm.c                | 4 ++++
>  drivers/mmc/host/sdhci.c                      | 9 +++++++++
>  drivers/mmc/host/sdhci.h                      | 4 ++++
>  4 files changed, 19 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
> index 22d1e1f..3a9be41 100644
> --- a/Documentation/devicetree/bindings/mmc/mmc.txt
> +++ b/Documentation/devicetree/bindings/mmc/mmc.txt
> @@ -52,6 +52,8 @@ Optional properties:
>  - no-sdio: controller is limited to send sdio cmd during initialization
>  - no-sd: controller is limited to send sd cmd during initialization
>  - no-mmc: controller is limited to send mmc cmd during initialization
> +- force-sd-cd-test-mode: card detection is broken on device, force cd test
> +  enable and cd test inserted so host will always detect a card.

Do not create a property that tells the driver what to do.

Instead create a property that says that the hardware is broken in a certain way.
The driver can then choose to take the appropriate action based on the way that
the hardware is broken.


>  
>  *NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line
>  polarity properties, we have to fix the meaning of the "normal" and "inverted"
> diff --git a/drivers/mmc/host/sdhci-pltfm.c b/drivers/mmc/host/sdhci-pltfm.c
> index 1d17dcf..056d101 100644
> --- a/drivers/mmc/host/sdhci-pltfm.c
> +++ b/drivers/mmc/host/sdhci-pltfm.c
> @@ -87,6 +87,10 @@ void sdhci_get_of_property(struct platform_device *pdev)
>  	if (of_get_property(np, "broken-cd", NULL))
>  		host->quirks |= SDHCI_QUIRK_BROKEN_CARD_DETECTION;
>  
> +	if (of_get_property(np, "force-sd-cd-test-mode", NULL))
> +		host->quirks2 |=
> +			SDHCI_QUIRK2_MUST_FORCE_SD_CD_TEST_MODE;
> +
>  	if (of_get_property(np, "no-1-8-v", NULL))
>  		host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
>  
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index cd65d47..2f4c6f9 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -117,6 +117,15 @@ static inline bool sdhci_data_line_cmd(struct mmc_command *cmd)
>  static void sdhci_set_card_detection(struct sdhci_host *host, bool enable)
>  {
>  	u32 present;
> +	u8  ctrl;
> +
> +	if (host->quirks2 & SDHCI_QUIRK2_MUST_FORCE_SD_CD_TEST_MODE) {
> +		/* Put the card in test mode, with card inserted */
> +		ctrl = sdhci_readl(host, SDHCI_HOST_CONTROL);
> +		ctrl |= SDHCI_CTRL_CD_TEST_INSERTED |
> +			SDHCI_CTRL_CD_TEST_ENABLE;
> +		sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
> +	}
>  
>  	if ((host->quirks & SDHCI_QUIRK_BROKEN_CARD_DETECTION) ||
>  	    !mmc_card_is_removable(host->mmc))
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 0411c9f..dd609b2 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -84,6 +84,8 @@
>  #define   SDHCI_CTRL_ADMA32	0x10
>  #define   SDHCI_CTRL_ADMA64	0x18
>  #define   SDHCI_CTRL_8BITBUS	0x20
> +#define  SDHCI_CTRL_CD_TEST_INSERTED	0x40
> +#define  SDHCI_CTRL_CD_TEST_ENABLE	0x80
>  
>  #define SDHCI_POWER_CONTROL	0x29
>  #define  SDHCI_POWER_ON		0x01
> @@ -422,6 +424,8 @@ struct sdhci_host {
>  #define SDHCI_QUIRK2_ACMD23_BROKEN			(1<<14)
>  /* Broken Clock divider zero in controller */
>  #define SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN		(1<<15)
> +/* Controller must support device with broken CD */
> +#define SDHCI_QUIRK2_MUST_FORCE_SD_CD_TEST_MODE		(1<<16)
>  
>  	int irq;		/* Device IRQ */
>  	void __iomem *ioaddr;	/* Mapped address */
>