linux-kernel - Re: [PATCH v1 2/2] mmc: sdhci: Use the SW timer when the HW timer cannot meet the timeout value required by the device

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Message-ID: <fc14d8e1-9438-d4b0-80f4-ccf9055ab7d3@intel.com>
Date:   Fri, 24 Sep 2021 08:29:51 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Bean Huo <huobean@...il.com>, Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Bean Huo <beanhuo@...ron.com>, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 2/2] mmc: sdhci: Use the SW timer when the HW timer
 cannot meet the timeout value required by the device

On 17/09/21 8:27 pm, Bean Huo wrote:
> From: Bean Huo <beanhuo@...ron.com>
> 
> If the data transmission timeout value required by the device exceeds
> the maximum timeout value of the host HW timer, we still use the HW
> timer with the maximum timeout value of the HW timer. This setting is
> suitable for most R/W situations. But sometimes, the device will complete
> the R/W task within its required timeout value (greater than the HW timer).
> In this case, the HW timer for data transmission will time out.
> 
> Currently, in this condition, we  disable the HW timer and use the SW
> timer only when the SDHCI_QUIRK2_DISABLE_HW_TIMEOUT quirk is set by the
> host driver. The patch is to remove this if statement restriction and
> allow data transmission to use the SW timer when the hardware timer cannot
> meet the required timeout value.

The reason it is a quirk is because it does not work for all hardware.
For some controllers the timeout cannot really be disabled, only the
interrupt is disabled, and then the controller never indicates completion
if the timeout is exceeded.

> 
> Signed-off-by: Bean Huo <beanhuo@...ron.com>
> ---
>  drivers/mmc/host/sdhci.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 357b365bf0ec..463517fd9886 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -969,9 +969,6 @@ static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_command *cmd,
>  		count++;
>  		current_timeout <<= 1;
>  		if (count > host->max_timeout_count) {
> -			if (!(host->quirks2 & SDHCI_QUIRK2_DISABLE_HW_TIMEOUT))
> -				DBG("Too large timeout 0x%x requested for CMD%d!\n",
> -				    count, cmd->opcode);
>  			count = host->max_timeout_count;
>  			*too_big = true;
>  			break;
> @@ -1016,8 +1013,7 @@ void __sdhci_set_timeout(struct sdhci_host *host, struct mmc_command *cmd)
>  	bool too_big = false;
>  	u8 count = sdhci_calc_timeout(host, cmd, &too_big);
>  
> -	if (too_big &&
> -	    host->quirks2 & SDHCI_QUIRK2_DISABLE_HW_TIMEOUT) {
> +	if (too_big) {
>  		sdhci_calc_sw_timeout(host, cmd);
>  		sdhci_set_data_timeout_irq(host, false);
>  	} else if (!(host->ier & SDHCI_INT_DATA_TIMEOUT)) {
>