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SubjectRe: [PATCH v2 11/16] mmc: sdhci: Program a relatively accurate SW timeout value
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On 05/02/18 14:50, 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 | 46 +++++++++++++++++++++++++++++++++++++++-------
> drivers/mmc/host/sdhci.h | 10 ++++++++++
> 2 files changed, 49 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 0489572d1892..d52f9e7eabe2 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -673,6 +673,37 @@ static void sdhci_adma_table_post(struct sdhci_host *host,
> }
> }
>
> +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;
> + unsigned long long transfer_time;
> + struct mmc_ios *ios = &mmc->ios;
> + unsigned char bus_width = ios->bus_width;
> + unsigned int blksz;
> + unsigned int freq;
> +
> + if (data) {
> + blksz = data->blksz;
> + freq = host->mmc->actual_clock ? host->mmc->actual_clock :
> + host->clock;

I think this can be:

freq = host->mmc->actual_clock ? : host->clock;

> + transfer_time = (unsigned long long)(blksz * NSEC_PER_SEC *
> + (8 / bus_width)) / freq;

You have got a 32-bit overflow here and a 64-bit division that can't always
be done with '/'

> + /* multiply by '2' to account for any unknowns */
> + transfer_time = transfer_time * 2;

transfer_time *= 2;

> + /* calculate timeout for the entire data */
> + host->data_timeout = (data->blocks * ((target_timeout *
> + NSEC_PER_USEC) +
> + transfer_time));
> + } else {
> + host->data_timeout = target_timeout * NSEC_PER_USEC;

And another 32-bit overflow here

> + }
> +
> + host->data_timeout += MMC_CMD_TRANSFER_TIME;
> +}
> +
> static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_command *cmd)
> {
> u8 count;
> @@ -742,6 +773,7 @@ static u8 sdhci_calc_timeout(struct sdhci_host *host, struct mmc_command *cmd)
> host->hw_timeout_disabled = true;
> }
> }
> + sdhci_calc_sw_timeout(host, cmd, target_timeout);
>
> return count;
> }
> @@ -1130,13 +1162,6 @@ 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, timeout);
> -
> host->cmd = cmd;
> if (sdhci_data_line_cmd(cmd)) {
> WARN_ON(host->data_cmd);
> @@ -1176,6 +1201,13 @@ 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 (sdhci_data_line_cmd(cmd))
> + timeout += nsecs_to_jiffies(host->data_timeout);
> + else
> + timeout += 10 * HZ;
> + sdhci_mod_timer(host, cmd, timeout);

Here you probably want to avoid updating the timer if the mrq has already
started using host->data_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 3a967a56fcc3..b73577d77856 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 400KHz clock should take 0.46ms.

I am not sure the math is correct here. I would add the 64 clocks before
the response also, and allow for 100 kHz clock.

(48 + 64 + 136) * 100 us = 24.8 ms

Given that you are looking at data block timeouts in excess of 700 ms, and
anything up to 10% of that is relatively negligible, anything less that 70
ms seems fine, so I would set 30 ms here as a round number.

> + * 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 2ms.
> + */
> +#define MMC_CMD_TRANSFER_TIME (2 * NSEC_PER_MSEC) /* max 2 ms */
> +
> enum sdhci_cookie {
> COOKIE_UNMAPPED,
> COOKIE_PRE_MAPPED, /* mapped by sdhci_pre_req() */
> @@ -554,6 +562,8 @@ struct sdhci_host {
> /* Host SDMA buffer boundary. */
> u32 sdma_boundary;
>
> + unsigned long long data_timeout;

nsecs_to_jiffies() uses u64 which is nicer I think

> +
> unsigned long private[0] ____cacheline_aligned;
> };
>
>

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