linux-kernel - Re: [PATCH] sdhci: always use max timeout for xfers

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Message-ID: <20110225180248.GA15491@pengutronix.de>
Date:	Fri, 25 Feb 2011 19:02:48 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Philip Rakity <prakity@...vell.com>
Cc:	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Jae hoon Chung <jh80.chung@...il.com>,
	Chuanxiao Dong <chuanxiao.dong@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sdhci: always use max timeout for xfers

Hi Philip,

On Fri, Feb 25, 2011 at 09:54:35AM -0800, Philip Rakity wrote:
> Rather then special case busy etc .. lets just use the max value.  

OK.

> 
> Did not remove BROKEN_TIMEOUT QUIRK so existing code will compile
> we can remove this once existing platform drivers delete usage and get
> quirk back.

If we wait for that, we'll probably wait till eternity ;) I'd vote that
removing the quirk should be part of the patch.

> 
> Patch starts after ====
> =====

The usual nomenclature is that such comments simply go between '---' and the
diffstat. Most tools are prepared for this...

> The card/host controller may sometimes return a value that is
> too low and cause the h/w to timeout a transfer that would have
> worked.  Using the maximum value avoids this.
> 
> Signed-off-by: Philip Rakity <prakity@...vell.com>
> ---

... to handle them here.

>  drivers/mmc/host/sdhci.c |   48 ++++-----------------------------------------
>  1 files changed, 5 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 655617c..dd99da8 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -592,53 +592,15 @@ static void sdhci_adma_table_post(struct sdhci_host *host,
>  		data->sg_len, direction);
>  }
>  
> -static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_data *data)
> +static inline u8 sdhci_calc_timeout(void)
>  {
> -	u8 count;
> -	unsigned target_timeout, current_timeout;
> -
>  	/*
> -	 * If the host controller provides us with an incorrect timeout
> -	 * value, just skip the check and use 0xE.  The hardware may take
> +	 * The host controller/card can provide us with an incorrect timeout
> +	 * value, just use the maximum value 0xE.  The hardware may take
>  	 * longer to time out, but that's much better than having a too-short
>  	 * timeout value.
>  	 */
> -	if (host->quirks & SDHCI_QUIRK_BROKEN_TIMEOUT_VAL)
> -		return 0xE;
> -
> -	/* timeout in us */
> -	target_timeout = data->timeout_ns / 1000 +
> -		data->timeout_clks / host->clock;
> -
> -	if (host->quirks & SDHCI_QUIRK_DATA_TIMEOUT_USES_SDCLK)
> -		host->timeout_clk = host->clock / 1000;

This quirk could go then as well?

> -
> -	/*
> -	 * Figure out needed cycles.
> -	 * We do this in steps in order to fit inside a 32 bit int.
> -	 * The first step is the minimum timeout, which will have a
> -	 * minimum resolution of 6 bits:
> -	 * (1) 2^13*1000 > 2^22,
> -	 * (2) host->timeout_clk < 2^16
> -	 *     =>
> -	 *     (1) / (2) > 2^6
> -	 */
> -	count = 0;
> -	current_timeout = (1 << 13) * 1000 / host->timeout_clk;
> -	while (current_timeout < target_timeout) {
> -		count++;
> -		current_timeout <<= 1;
> -		if (count >= 0xF)
> -			break;
> -	}
> -
> -	if (count >= 0xF) {
> -		printk(KERN_WARNING "%s: Too large timeout requested!\n",
> -			mmc_hostname(host->mmc));
> -		count = 0xE;
> -	}
> -
> -	return count;
> +	return 0xE;

Why don't you remove the function entirely?

>  }
>  
>  static void sdhci_set_transfer_irqs(struct sdhci_host *host)
> @@ -671,7 +633,7 @@ static void sdhci_prepare_data(struct sdhci_host *host, struct mmc_data *data)
>  	host->data = data;
>  	host->data_early = 0;
>  
> -	count = sdhci_calc_timeout(host, data);
> +	count = sdhci_calc_timeout();
>  	sdhci_writeb(host, count, SDHCI_TIMEOUT_CONTROL);
>  
>  	if (host->flags & (SDHCI_USE_SDMA | SDHCI_USE_ADMA))

Thanks,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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