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

[Kishon Vijay Abraham I <kishon@ti.com>]

Hi Adrian,

On Friday 16 March 2018 07:51 PM, Adrian Hunter wrote:
> On 16/03/18 08:29, Kishon Vijay Abraham I wrote:
>> 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@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;
>>
>> sdhci_calc_sw_timeout should have calculated the timeout for this case too no?
> 
> Yes, but I was thinking you would only calculate when it was needed.

I feel since we would have anyways calculated data_timeout, we should use that
instead unless you see a problem with that.

Thanks
Kishon