Re: [PATCH v2] mmc: dw_mmc: Allow lower TMOUT value than maximum

[Jaehoon Chung <jh80.chung@samsung.com>]

Hi Marten,

On 11/8/21 8:36 PM, Mårten Lindahl wrote:
> The TMOUT register is always set with a full value for every transfer,
> which (with a 200MHz clock) will give a full DRTO of ~84 milliseconds.
> Since the software dto_timer acts as a backup in cases when this timeout
> is not long enough, it is normally not a problem. But setting a full
> value makes it impossible to test shorter timeouts, when for example
> testing data read times on different SD cards.
> 
> Add a function to set any value smaller than the maximum of 0xFFFFFF.
> 
> Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
> ---
> 
> v2:
>  - Calculate new value before checking boundaries
>  - Include CLKDIV register to get proper value
> 
>  drivers/mmc/host/dw_mmc.c | 32 +++++++++++++++++++++++++++++++-
>  1 file changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index 6578cc64ae9e..6edd7a231448 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1283,6 +1283,36 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
>  	mci_writel(host, CTYPE, (slot->ctype << slot->id));
>  }
>  
> +static void dw_mci_set_data_timeout(struct dw_mci *host,
> +				    unsigned int timeout_ns)
> +{
> +	unsigned int clk_div, tmp, tmout;
> +
> +	clk_div = (mci_readl(host, CLKDIV) & 0xFF) * 2;
> +	if (clk_div == 0)
> +		clk_div = 1;
> +
> +	tmp = DIV_ROUND_UP_ULL((u64)timeout_ns * host->bus_hz,
> +			       NSEC_PER_SEC * clk_div);
> +
> +	if (!tmp || tmp > 0xFFFFFF) {
> +		/* Set maximum */

"Set maximum value about all Timeout"?

> +		tmout = 0xFFFFFFFF;
> +		goto tmout_done;
> +	}

It doesn't need to use "goto". Instead, if-else can be used.

> +
> +	/* TMOUT[7:0] (RESPONSE_TIMEOUT) */
> +	tmout = 0xFF; /* Set maximum */

To prevent a confusion, how about add "Set a maximum response timeout"
And this line can be removed.

> +
> +	/* TMOUT[31:8] (DATA_TIMEOUT) */
> +	tmout |= (tmp & 0xFFFFFF) << 8;

tmout = (0xFF | ((tmp & 0xFFFFFF) << 8));

The entire code can be below

if (!tmp || ....)
	tmout = 0xFFFFFFFF;
else 
	tmout = (0xFF | ((tmp & 0xFFFFFF) << 8));

writel(TMOUT, ...)

How about this?

Best Regards,
Jaehoon Chung

> +
> +tmout_done:
> +	mci_writel(host, TMOUT, tmout);
> +	dev_dbg(host->dev, "timeout_ns: %u => TMOUT[31:8]: 0x%06x",
> +		timeout_ns, tmout >> 8);
> +}
> +
>  static void __dw_mci_start_request(struct dw_mci *host,
>  				   struct dw_mci_slot *slot,
>  				   struct mmc_command *cmd)
> @@ -1303,7 +1333,7 @@ static void __dw_mci_start_request(struct dw_mci *host,
>  
>  	data = cmd->data;
>  	if (data) {
> -		mci_writel(host, TMOUT, 0xFFFFFFFF);
> +		dw_mci_set_data_timeout(host, data->timeout_ns);
>  		mci_writel(host, BYTCNT, data->blksz*data->blocks);
>  		mci_writel(host, BLKSIZ, data->blksz);
>  	}
>