linux-kernel - Re: [PATCH] mmc: omap_hsmmc: clear status flags before starting a new command

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Message-ID: <87vc2uttn3.fsf@octavius.laptop.org>
Date:	Sat, 24 Aug 2013 22:02:24 -0400
From:	Chris Ball <cjb@...top.org>
To:	Francesco Lavra <francescolavra.fl@...il.com>
Cc:	Balaji T K <balajitk@...com>, linux-mmc@...r.kernel.org,
	linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: omap_hsmmc: clear status flags before starting a new command

Hi Balaji,

On Sat, Jun 29 2013, Francesco Lavra wrote:
> Commit 1f6b9fa40e76fffaaa0b3bd6a0bfdcf1cdc06efa consolidated writes to 
> the STAT register in one location, moving them from omap_hsmmc_do_irq() 
> to omap_hsmmc_irq(). This move has the unwanted side effect that the 
> controller status flags are potentially cleared after a new command has 
> been started as a consequence of reading the previous status flags. 
> This means that if the new command changes the status flags before the 
> IRQ routine returns, those flags may be cleared without handling the 
> event which asserted them, and thus missing the event.
> Move the writing of the STAT register back in omap_hsmmc_do_irq(), 
> before handling the status flags which generated the interrupt.
>
> Signed-off-by: Francesco Lavra <francescolavra.fl@...il.com>
> ---
>  drivers/mmc/host/omap_hsmmc.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> index eccedc7..301cb7e 100644
> --- a/drivers/mmc/host/omap_hsmmc.c
> +++ b/drivers/mmc/host/omap_hsmmc.c
> @@ -1041,6 +1041,7 @@ static void omap_hsmmc_do_irq(struct omap_hsmmc_host *host, int status)
>  		}
>  	}
>  
> +	OMAP_HSMMC_WRITE(host->base, STAT, status);
>  	if (end_cmd || ((status & CC_EN) && host->cmd))
>  		omap_hsmmc_cmd_done(host, host->cmd);
>  	if ((end_trans || (status & TC_EN)) && host->mrq)
> @@ -1060,7 +1061,6 @@ static irqreturn_t omap_hsmmc_irq(int irq, void *dev_id)
>  		omap_hsmmc_do_irq(host, status);
>  
>  		/* Flush posted write */
> -		OMAP_HSMMC_WRITE(host->base, STAT, status);
>  		status = OMAP_HSMMC_READ(host->base, STAT);
>  	}

Please could you review this patch?  Thanks,

- Chris.
-- 
Chris Ball   <cjb@...top.org>   <http://printf.net/>
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