linux-kernel - Re: [RFC PATCH 2/2] mmc: Allow tuning to be skipped during card init

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Message-ID: <93f9d38e-60b3-4090-91e7-aebf1ddb72dc@ti.com>
Date: Tue, 28 Jan 2025 10:04:38 -0600
From: Judith Mendez <jm@...com>
To: Erick Shepherd <erick.shepherd@...com>, <linux-kernel@...r.kernel.org>
CC: <linux-mmc@...r.kernel.org>, <york.yang@....com>, <ulf.hansson@...aro.org>
Subject: Re: [RFC PATCH 2/2] mmc: Allow tuning to be skipped during card init

Hi Erick,

On 1/27/25 4:36 PM, Erick Shepherd wrote:
> Add a new field to the mmc_host struct to track when the card should
> skip the initial tuning and use it to conditionally stop tuning in the
> mmc_sd_init_uhs_card function. Currently the new field only gets set
> when a DDR50 card fails to tune, which indicates the card does not
> support tuning.

Just out of curiosity, why do we want to stop the initial tuning?

~ Judith

> 
> Signed-off-by: Erick Shepherd <erick.shepherd@...com>
> ---
>   drivers/mmc/core/sd.c    | 4 +++-
>   include/linux/mmc/host.h | 1 +
>   2 files changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index cc757b850e79..353715fd8f53 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -663,7 +663,8 @@ static int mmc_sd_init_uhs_card(struct mmc_card *card)
>   	if (!mmc_host_is_spi(card->host) &&
>   		(card->host->ios.timing == MMC_TIMING_UHS_SDR50 ||
>   		 card->host->ios.timing == MMC_TIMING_UHS_DDR50 ||
> -		 card->host->ios.timing == MMC_TIMING_UHS_SDR104)) {
> +		 card->host->ios.timing == MMC_TIMING_UHS_SDR104) &&
> +		!card->host->skip_init_tune) {
>   		err = mmc_execute_tuning(card);
>   
>   		/*
> @@ -676,6 +677,7 @@ 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->host->skip_init_tune = 1;
>   			err = 0;
>   		}
>   	}
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 68f09a955a90..91c4db6837c9 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -486,6 +486,7 @@ struct mmc_host {
>   	unsigned int		use_spi_crc:1;
>   	unsigned int		claimed:1;	/* host exclusively claimed */
>   	unsigned int		doing_init_tune:1; /* initial tuning in progress */
> +	unsigned int		skip_init_tune:1;	/* skip the initial tuning */
>   	unsigned int		can_retune:1;	/* re-tuning can be used */
>   	unsigned int		doing_retune:1;	/* re-tuning in progress */
>   	unsigned int		retune_now:1;	/* do re-tuning at next req */