linux-kernel - Re: [RFC PATCH V2 2/2] mmc: allow card to disable tuning

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Message-ID: <c1863075-90bb-486a-bd25-b8ea6b2ae035@intel.com>
Date: Sat, 15 Feb 2025 03:08:48 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Erick Shepherd <erick.shepherd@...com>, <linux-kernel@...r.kernel.org>
CC: <linux-mmc@...r.kernel.org>, <ulf.hansson@...aro.org>,
	<avri.altman@....com>, <wsa+renesas@...g-engineering.com>,
	<quic_jjohnson@...cinc.com>, <andy-ld.lu@...iatek.com>,
	<victor.shih@...esyslogic.com.tw>, <keita.aihara@...y.com>,
	<dsimic@...jaro.org>, <cw9316.lee@...sung.com>, <ricardo@...liere.net>
Subject: Re: [RFC PATCH V2 2/2] mmc: allow card to disable tuning

On 6/02/25 23:08, Erick Shepherd wrote:
> Add a new field to the mmc_card struct to disable tuning for the card.
> Currently the new field only gets set when a DDR50 card fails to tune,
> which indicates the card does not support tuning.

You need to explain why this is needed.  Presumably it speeds up
runtime-resume in some cases?

> 
> Signed-off-by: Erick Shepherd <erick.shepherd@...com>
> ---
>  drivers/mmc/core/core.c  | 3 +++
>  drivers/mmc/core/sd.c    | 1 +
>  include/linux/mmc/card.h | 1 +
>  3 files changed, 5 insertions(+)
> 
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 5241528f8b90..ee91d53c45d5 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -934,6 +934,9 @@ int mmc_execute_tuning(struct mmc_card *card)
>  	u32 opcode;
>  	int err;
>  
> +	if (card->disable_tuning)
> +		return 0;
> +
>  	if (!host->ops->execute_tuning)
>  		return 0;
>  
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index cc757b850e79..dd65485c61d8 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -676,6 +676,7 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
>  		if (err && card->host->ios.timing == MMC_TIMING_UHS_DDR50) {
>  			pr_warn("%s: ddr50 tuning failed\n",
>  				mmc_hostname(card->host));
> +			card->disable_tuning = true;
>  			err = 0;
>  		}
>  	}
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 526fce581657..f9733c7ce430 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -332,6 +332,7 @@ struct mmc_card {
>  
>  	bool			written_flag;	/* Indicates eMMC has been written since power on */
>  	bool			reenable_cmdq;	/* Re-enable Command Queue */
> +	bool			disable_tuning;	/* Disables tuning for the card */
>  
>  	unsigned int		erase_size;	/* erase size in sectors */
>   	unsigned int		erase_shift;	/* if erase unit is power 2 */