linux-kernel - Re: SDHCI - Add QUIRK2_BROKEN_WRITE_PROTEXT

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Date:	Tue, 20 Aug 2013 14:54:02 +0200
From:	Michal Simek <monstr@...str.eu>
To:	James Walmsley <james@...lfat-fs.co.uk>,
	Chris Ball <cjb@...top.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-mmc@...r.kernel.org
Subject: Re: SDHCI - Add QUIRK2_BROKEN_WRITE_PROTEXT - Support Xilinx Zynq
 (Linux 3.9.0)

Hi James,

isn't it better to implement host->ops->get_ro() function for it?
It seems me better choice than introducing new quirk option.

Chris: What do you think?

Thanks,
Michal


On 08/16/2013 02:14 PM, James Walmsley wrote:
> Hi Michal,
> 
> I have built a Xilinx Zynq based design which doesn't use the SDHCI Write-protect line.
> However, we use the MIO_0 pin for configuring a multiplexer and consequently the
> SDHCI driver thinks that the card is read-only (RO).
> 
> In the patch below I have proposed a new quirk, similar to the QUIRK_BROKEN_CARD_DETECTION
> flag, which causes the sdhci driver to assume a card with RW access.
> 
> This patch was made against the latest tree from Xilinx (github.com/Xilinx/linux-xlnx), Kernel 3.9.0
> and I have attached it to the LKML to propose the additional quirk which may be useful on other platforms.
> 
> Kind regards,
> 
> James Walmsley
> 
> ---
>  drivers/mmc/host/sdhci-of-xilinxps.c | 4 ++++
>  drivers/mmc/host/sdhci.c             | 4 ++++
>  include/linux/mmc/sdhci.h            | 1 +
>  3 files changed, 9 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-of-xilinxps.c b/drivers/mmc/host/sdhci-of-xilinxps.c
> index f79e0db..5553bc0 100644
> --- a/drivers/mmc/host/sdhci-of-xilinxps.c
> +++ b/drivers/mmc/host/sdhci-of-xilinxps.c
> @@ -211,6 +211,10 @@ static int sdhci_zynq_probe(struct platform_device *pdev)
>  	if (prop == NULL || (!(u32) be32_to_cpup(prop)))
>  		host->quirks |= SDHCI_QUIRK_BROKEN_CARD_DETECTION;
>  
> +	prop = of_get_property(np, "xlnx,has-wp", NULL);
> +	if (prop == NULL || (!(u32) be32_to_cpup(prop)))
> +		host->quirks2 |= SDHCI_QUIRK2_BROKEN_WRITE_PROTECT;
> +
>  	return 0;
>  
>  clk_notif_unreg:
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 51bbba4..c40365f 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1609,6 +1609,10 @@ static int sdhci_do_get_ro(struct sdhci_host *host)
>  {
>  	int i, ro_count;
>  
> +	if(host->quirks2 & SDHCI_QUIRK2_BROKEN_WRITE_PROTECT) {
> +		return 0;	// Return zero to assume RW.
> +	}
> +
>  	if (!(host->quirks & SDHCI_QUIRK_UNSTABLE_RO_DETECT))
>  		return sdhci_check_ro(host);
>  
> diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
> index b838ffc..3eccf12 100644
> --- a/include/linux/mmc/sdhci.h
> +++ b/include/linux/mmc/sdhci.h
> @@ -95,6 +95,7 @@ struct sdhci_host {
>  /* The system physically doesn't support 1.8v, even if the host does */
>  #define SDHCI_QUIRK2_NO_1_8_V				(1<<2)
>  #define SDHCI_QUIRK2_PRESET_VALUE_BROKEN		(1<<3)
> +#define SDHCI_QUIRK2_BROKEN_WRITE_PROTECT		(1<<4)
>  
>  	int irq;		/* Device IRQ */
>  	void __iomem *ioaddr;	/* Mapped address */
> 


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform



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