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

[Adrian Hunter]

On 19/03/18 11:20, Kishon Vijay Abraham I wrote:
> 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@xxxxxx>
>>>>> ---
>>>>>  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.

I would prefer not to calculate data_timeout when a hardware timeout is
being used.