linux-kernel - Re: [PATCH V4 02/10] mmc: sdhci: allow host to specify maximum tuning loops

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Date:   Mon, 25 Mar 2019 12:25:38 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        ulf.hansson@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
        riteshh@...eaurora.org
Cc:     thierry.reding@...il.com, jonathanh@...dia.com, anrao@...dia.com,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH V4 02/10] mmc: sdhci: allow host to specify maximum tuning
 loops

On 24/03/19 6:45 AM, Sowjanya Komatineni wrote:
> As per the Host Controller Standard Specification Version 4.20,
> limitation of tuning iteration count is removed as PLL locking
> time can be longer than UHS-1 tuning due to larger PVT fluctuation
> and it will result in increase of tuning iteration to complete the
> tuning.
> 
> This patch creates sdhci_host member tuning_loop_count to allow
> hosts to specify maximum tuning iterations and also updates
> execute_tuning to use this specified maximum tuning iteration count.
> 
> Default tuning_loop_count is set to same as existing loop count of
> MAX_TUNING_LOOP which is 40 iterations.
> 
> Tested-by: Jon Hunter <jonathanh@...dia.com>
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  drivers/mmc/host/sdhci.c | 5 +++--
>  drivers/mmc/host/sdhci.h | 1 +
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index a8141ff9be03..bbc0e0bb7128 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2369,9 +2369,9 @@ static int __sdhci_execute_tuning(struct sdhci_host *host, u32 opcode)
>  
>  	/*
>  	 * Issue opcode repeatedly till Execute Tuning is set to 0 or the number
> -	 * of loops reaches 40 times.
> +	 * of loops reaches tuning loop count.
>  	 */
> -	for (i = 0; i < MAX_TUNING_LOOP; i++) {
> +	for (i = 0; i < host->tuning_loop_count; i++) {
>  		u16 ctrl;
>  
>  		sdhci_send_tuning(host, opcode);
> @@ -3494,6 +3494,7 @@ struct sdhci_host *sdhci_alloc_host(struct device *dev,
>  	host->cqe_err_ier = SDHCI_CQE_INT_ERR_MASK;
>  
>  	host->tuning_delay = -1;
> +	host->tuning_loop_count = MAX_TUNING_LOOP;
>  
>  	host->sdma_boundary = SDHCI_DEFAULT_BOUNDARY_ARG;
>  
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 01002cba1359..57bb3e3dca89 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -596,6 +596,7 @@ struct sdhci_host {
>  #define SDHCI_TUNING_MODE_3	2
>  	/* Delay (ms) between tuning commands */
>  	int			tuning_delay;
> +	int			tuning_loop_count;
>  
>  	/* Host SDMA buffer boundary. */
>  	u32			sdma_boundary;
>