linux-kernel - Re: [PATCH 4/6] Unified AVR32/AT91 MCI Driver

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Date:	Fri, 12 Jun 2009 18:08:00 -0700
From:	Rob Emanuele <poorarm@...reis.com>
To:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
Cc:	Andrew Victor <avictor.za@...il.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-kernel@...r.kernel.org, drzeus-mmc@...eus.cx
Subject: Re: [PATCH 4/6] Unified AVR32/AT91 MCI Driver

Please disregard this patch/message as the subject is incorrect.

Thank you,

Rob Emanuele

On Fri, Jun 12, 2009 at 6:02 PM, Rob Emanuele<poorarm@...reis.com> wrote:
> This patch adds the compile time configuration option for the
> atmel-mci driver to cap the MCI CLKDIV register value to a minimum
> value.
>
> This is useful for debugging and for boards that have a long mci clock line.
>
> Please read the whole set, try it out, and comment.
>
> Thank you,
>
> Rob Emanuele
>
> ---
>  drivers/mmc/host/Kconfig     |   14 ++++++++++++++
>  drivers/mmc/host/atmel-mci.c |   10 ++++++++++
>  2 files changed, 24 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> index 9e24029..9f797b2 100644
> --- a/drivers/mmc/host/Kconfig
> +++ b/drivers/mmc/host/Kconfig
> @@ -150,6 +150,20 @@ config MMC_ATMELMCI
>
>  endchoice
>
> +config MMC_ATMELMCI_CLKDIV_CAP
> +       int "Cap the CLKDIV to keep the controller from going too fast."
> +       depends on MMC_ATMELMCI
> +       default 0
> +       range 0 255
> +       help
> +         This is the lowest value the clock divisor for the MMC
> +         controller can be.  Value is between 0 and 255.
> +         MCI_CK = MCK/(2*(CLKDIV+1))
> +         Raising this value may improve your controller's reliability
> +         at the cost of speed.
> +
> +         If unsure, leave at 0.
> +
>  config MMC_ATMELMCI_ALWAYS_RESET
>        bool "Reset before every request.  Sometimes needed for buggy chips."
>        depends on MMC_ATMELMCI
> diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
> index b133baa..1c1a4b3 100644
> --- a/drivers/mmc/host/atmel-mci.c
> +++ b/drivers/mmc/host/atmel-mci.c
> @@ -74,6 +74,10 @@ struct atmel_mci_dma {
>  #define MMC_ALWAYS_RESET 0
>  #endif
>
> +#ifndef CONFIG_MMC_ATMELMCI_CLKDIV_CAP
> +#define CONFIG_MMC_ATMELMCI_CLKDIV_CAP 0
> +#endif
> +
>  /**
>  * struct atmel_mci - MMC controller state shared between all slots
>  * @lock: Spinlock protecting the queue and associated data.
> @@ -876,6 +880,12 @@ static void atmci_set_ios(struct mmc_host *mmc,
> struct mmc_ios *ios)
>                                clock_min, host->bus_hz / (2 * 256));
>                        clkdiv = 255;
>                }
> +               if (clkdiv < CONFIG_MMC_ATMELMCI_CLKDIV_CAP) {
> +                       dev_warn(&mmc->class_dev,
> +                               "clkdiv %u too fast; capped using %u\n",
> +                                clkdiv, CONFIG_MMC_ATMELMCI_CLKDIV_CAP);
> +                       clkdiv = CONFIG_MMC_ATMELMCI_CLKDIV_CAP;
> +               }
>
>                host->mode_reg = MCI_MR_CLKDIV(clkdiv);
>
> --
> 1.6.0.4
>
--
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