why not just not compile the the code without clock gating defined ?

and if code cannot run with it clock gating defined do a 
#error ?

Also from the diff I think you patch changes the behavior of SD/eMMC cards which may not be what you want .


On Jan 2, 2011, at 1:08 PM, Pierre Tardy wrote:

quoted text
> Some sdio card are not following sdio standard, and does not work
> when the sdio bus's clock is gated
> 
> To keep functionnality for all legacy driver, we turn this quirk on
> for every sdio card.
> Drivers needs to disable the quirk manually when someone verified that their
> supported card works with clock gating.
> 
> Signed-off-by: Pierre Tardy <tardyp@gmail.com>
> ---
> drivers/mmc/core/host.c  |    5 +----
> drivers/mmc/core/sdio.c  |    6 ++++++
> include/linux/mmc/card.h |    1 +
> 3 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 92e3370..54cc461 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -160,10 +160,7 @@ static bool mmc_host_may_gate_card(struct mmc_card *card)
> 	 * gate the clock, because there is somebody out there that may still
> 	 * be using it.
> 	 */
> -	if (mmc_card_sdio(card))
> -		return false;
> -
> -	return true;
> +	return !(card->quirks & MMC_QUIRK_BROKEN_CLK_GATING);
> }
> 
> /**
> diff --git a/drivers/mmc/core/sdio.c b/drivers/mmc/core/sdio.c
> index 82f4b90..6df1ead 100644
> --- a/drivers/mmc/core/sdio.c
> +++ b/drivers/mmc/core/sdio.c
> @@ -785,6 +785,12 @@ int mmc_attach_sdio(struct mmc_host *host, u32 ocr)
> 
> 	mmc_release_host(host);
> 
> +        /*
> +         * see comments in mmc_host_may_gate_card()
> +         * this can be overidden by function drivers if they know that
> +         * their sdio card works with clock gating
> +         */
> +        card->quirks |= MMC_QUIRK_BROKEN_CLK_GATING;
> 	/*
> 	 * First add the card to the driver model...
> 	 */
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 8ce0827..5071eb1 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -121,6 +121,7 @@ struct mmc_card {
> 						/* for byte mode */
> #define MMC_QUIRK_NONSTD_SDIO	(1<<2)		/* non-standard SDIO card attached */
> 						/* (missing CIA registers) */
> +#define MMC_QUIRK_BROKEN_CLK_GATING (1<<3)	/* clock gating the sdio bus will make card fail */
> 
> 	unsigned int		erase_size;	/* erase size in sectors */
>  	unsigned int		erase_shift;	/* if erase unit is power 2 */
> -- 
> 1.7.1
> 
> --
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