[v2, 4/7] mmc: sdhci: add a quirk to restore delay in tuning

[Y.B. Lu]

Hi Adrian,

Thanks a lot for your suggestion.
I have sent out the new version patch-set.

Please help to review :)


Best regards,
Yangbo Lu

> -----Original Message-----
> From: Adrian Hunter [mailto:adrian.hunter at intel.com]
> Sent: Thursday, March 23, 2017 3:04 PM
> To: Y.B. Lu; linux-mmc at vger.kernel.org; ulf.hansson at linaro.org; Rob
> Herring; Mark Rutland; Catalin Marinas; Will Deacon
> Cc: devicetree at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
> Xiaobo Xie
> Subject: Re: [v2, 4/7] mmc: sdhci: add a quirk to restore delay in tuning
> 
> On 03/03/17 10:18, Yangbo Lu wrote:
> > There was a mdelay between tuning cycles which is removed since eMMC
> > spec didn't require that. However it's observed that eSDHC needed this
> > delay for HS200 successful tuning. Maybe it's also needed for some
> > other controllers. This patch is to add a quirk to fix it.
> >
> > Fixes: 197160d52e85 ("mmc: sdhci: remove mdelay in eMMC tuning")
> > Signed-off-by: Yangbo Lu <yangbo.lu at nxp.com>
> > ---
> 
> I would prefer to do something like this:
> 
> ---
> From: Adrian Hunter <adrian.hunter at intel.com>
> Date: Thu, 23 Mar 2017 08:54:06 +0200
> Subject: [PATCH] mmc: sdhci: Control the delay between tuning commands
> 
> The delay between tuning commands for SD cards is not part of the
> specification. A driver that needs it probably needs it for eMMC too,
> whereas most drivers would probably like to set it to 0. Make it a host
> member (host->tuning_delay) that defaults to the existing behaviour.
> Drivers can set it to zero to eliminate the delay, or set it to a
> positive value to always have a delay.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter at intel.com>
> ---
>  drivers/mmc/host/sdhci.c | 11 ++++++++---  drivers/mmc/host/sdhci.h |  1
> +
>  2 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index
> a33102fc800b..2fc33485df1d 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2100,9 +2100,9 @@ static void __sdhci_execute_tuning(struct
> sdhci_host *host, u32 opcode)
>  			break;
>  		}
> 
> -		/* eMMC spec does not require a delay between tuning cycles
> */
> -		if (opcode == MMC_SEND_TUNING_BLOCK)
> -			mdelay(1);
> +		/* Spec does not require a delay between tuning cycles */
> +		if (host->tuning_delay > 0)
> +			mdelay(host->tuning_delay);
>  	}
> 
>  	pr_info("%s: Tuning failed, falling back to fixed sampling clock\n",
> @@ -2164,6 +2164,9 @@ int sdhci_execute_tuning(struct mmc_host *mmc, u32
> opcode)
> 
>  	host->mmc->retune_period = tuning_count;
> 
> +	if (host->tuning_delay < 0)
> +		host->tuning_delay = opcode == MMC_SEND_TUNING_BLOCK;
> +
>  	sdhci_start_tuning(host);
> 
>  	__sdhci_execute_tuning(host, opcode);
> @@ -3108,6 +3111,8 @@ struct sdhci_host *sdhci_alloc_host(struct device
> *dev,
>  	host->cqe_ier     = SDHCI_CQE_INT_MASK;
>  	host->cqe_err_ier = SDHCI_CQE_INT_ERR_MASK;
> 
> +	host->tuning_delay = -1;
> +
>  	return host;
>  }
> 
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h index
> 35b41da0a636..b0f416fc9548 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -538,6 +538,7 @@ struct sdhci_host {
>  #define SDHCI_TUNING_MODE_1	0
>  #define SDHCI_TUNING_MODE_2	1
>  #define SDHCI_TUNING_MODE_3	2
> +	int			tuning_delay;	/* Delay (ms) between tuning
> commands */
> 
>  	unsigned long private[0] ____cacheline_aligned;  };
> --
> 1.9.1
> 
>