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

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Message-ID: <47752066-aeda-87bc-6928-1a9b80f1c45c@ti.com>
Date:   Fri, 16 Mar 2018 11:59:27 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Tony Lindgren <tony@...mide.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        <linux-mmc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 07/11] mmc: sdhci: Program a relatively accurate SW
 timeout value

Hi,

On Thursday 15 March 2018 06:43 PM, Adrian Hunter wrote:
> 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@...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;

sdhci_calc_sw_timeout should have calculated the timeout for this case too no?

Thanks
Kishon