Re: [PATCH v3 07/11] mmc: sdhci: Program a relatively accurate SW timeout value

[Adrian Hunter <adrian.hunter@intel.com>]

On 07/03/18 15:20, Kishon Vijay Abraham I wrote:
> sdhci has a 10 second timeout to catch devices that stop responding.
> Instead of programming 10 second arbitrary value, calculate the total time
> it would take for the entire transfer to happen and program the timeout
> value accordingly.
> 
> Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
> ---
>  drivers/mmc/host/sdhci.c | 47 ++++++++++++++++++++++++++++++++++++++++-------
>  drivers/mmc/host/sdhci.h | 10 ++++++++++
>  2 files changed, 50 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 1dd117cbeb6e..baab67bfa39b 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -709,6 +709,36 @@ static u32 sdhci_sdma_address(struct sdhci_host *host)
>  		return sg_dma_address(host->data->sg);
>  }
>  
> +static void sdhci_calc_sw_timeout(struct sdhci_host *host,
> +				  struct mmc_command *cmd,
> +				  unsigned int target_timeout)
> +{
> +	struct mmc_data *data = cmd->data;
> +	struct mmc_host *mmc = host->mmc;
> +	u64 transfer_time;
> +	struct mmc_ios *ios = &mmc->ios;
> +	unsigned char bus_width = 1 << ios->bus_width;
> +	unsigned int blksz;
> +	unsigned int freq;
> +
> +	if (data) {
> +		blksz = data->blksz;
> +		freq = host->mmc->actual_clock ? : host->clock;
> +		transfer_time = (u64)blksz * NSEC_PER_SEC * (8 / bus_width);
> +		do_div(transfer_time, freq);
> +		/* multiply by '2' to account for any unknowns */
> +		transfer_time = transfer_time * 2;
> +		/* calculate timeout for the entire data */
> +		host->data_timeout = (data->blocks * ((target_timeout *
> +						       NSEC_PER_USEC) +
> +						       transfer_time));

(target_timeout * NSEC_PER_USEC) might be 32-bit and therefore overflow
for timeouts greater than about 4 seconds.

> +	} else {
> +		host->data_timeout = (u64)target_timeout * NSEC_PER_USEC;
> +	}
> +
> +	host->data_timeout += MMC_CMD_TRANSFER_TIME;

Need to allow for target_timeout == 0 so:

	if (host->data_timeout)
		host->data_timeout += MMC_CMD_TRANSFER_TIME;

> +}
> +
>  static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_command *cmd)
>  {
>  	u8 count;
> @@ -766,6 +796,7 @@ static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_command *cmd)
>  		if (count >= 0xF)
>  			break;
>  	}
> +	sdhci_calc_sw_timeout(host, cmd, target_timeout);

If you make the changes I suggest for patch 6, then this would
move sdhci_calc_sw_timeout() into sdhci_set_timeout().

I suggest you factor out the target_timeout calculation e.g.

static unsigned int sdhci_target_timeout(struct sdhci_host *host,
					 struct mmc_command *cmd,
					 struct mmc_data *data)
{
	unsigned int target_timeout;

	/* timeout in us */
	if (!data)
		target_timeout = cmd->busy_timeout * 1000;
	else {
		target_timeout = DIV_ROUND_UP(data->timeout_ns, 1000);
		if (host->clock && data->timeout_clks) {
			unsigned long long val;

			/*
			 * data->timeout_clks is in units of clock cycles.
			 * host->clock is in Hz.  target_timeout is in us.
			 * Hence, us = 1000000 * cycles / Hz.  Round up.
			 */
			val = 1000000ULL * data->timeout_clks;
			if (do_div(val, host->clock))
				target_timeout++;
			target_timeout += val;
		}
	}

	return target_timeout;
}

And call it from sdhci_calc_sw_timeout()

>  
>  	return count;
>  }
> @@ -1175,13 +1206,6 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
>  		mdelay(1);
>  	}
>  
> -	timeout = jiffies;
> -	if (!cmd->data && cmd->busy_timeout > 9000)
> -		timeout += DIV_ROUND_UP(cmd->busy_timeout, 1000) * HZ + HZ;
> -	else
> -		timeout += 10 * HZ;
> -	sdhci_mod_timer(host, cmd->mrq, timeout);
> -
>  	host->cmd = cmd;
>  	if (sdhci_data_line_cmd(cmd)) {
>  		WARN_ON(host->data_cmd);
> @@ -1221,6 +1245,15 @@ void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
>  	    cmd->opcode == MMC_SEND_TUNING_BLOCK_HS200)
>  		flags |= SDHCI_CMD_DATA;
>  
> +	timeout = jiffies;
> +	if (host->data_timeout > 0) {

This can be just:

	if (host->data_timeout) {

> +		timeout += nsecs_to_jiffies(host->data_timeout);
> +		host->data_timeout = 0;

It would be better to initialize host->data_timeout = 0 at the top of
sdhci_prepare_data().

Also still need:

	else if (!cmd->data && cmd->busy_timeout > 9000) {
		timeout += DIV_ROUND_UP(cmd->busy_timeout, 1000) * HZ + HZ;


> +	} else {
> +		timeout += 10 * HZ;
> +	}
> +	sdhci_mod_timer(host, cmd->mrq, timeout);
> +
>  	sdhci_writew(host, SDHCI_MAKE_CMD(cmd->opcode, flags), SDHCI_COMMAND);
>  }
>  EXPORT_SYMBOL_GPL(sdhci_send_command);
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index ff283ee08854..29b242fd17de 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -332,6 +332,14 @@ struct sdhci_adma2_64_desc {
>  /* Allow for a a command request and a data request at the same time */
>  #define SDHCI_MAX_MRQS		2
>  
> +/*
> + * 48bit command and 136 bit response in 100KHz clock could take upto 2.48ms.
> + * However since the start time of the command, the time between
> + * command and response, and the time between response and start of data is
> + * not known, set the command transfer time to 10ms.
> + */
> +#define MMC_CMD_TRANSFER_TIME	(10 * NSEC_PER_MSEC) /* max 10 ms */
> +
>  enum sdhci_cookie {
>  	COOKIE_UNMAPPED,
>  	COOKIE_PRE_MAPPED,	/* mapped by sdhci_pre_req() */
> @@ -555,6 +563,8 @@ struct sdhci_host {
>  	/* Host SDMA buffer boundary. */
>  	u32			sdma_boundary;
>  
> +	u64			data_timeout;
> +
>  	unsigned long private[0] ____cacheline_aligned;
>  };
>  
>