[PATCH v1] i.MX: esdhc: optimize set_ios path

[Sascha Hauer]

On Wed, Nov 08, 2017 at 04:33:08PM +0100, Oleksij Rempel wrote:
> this part of code is executed at least 4 times in eMMC probe sequence.
> Optimizing it is reducing 20-30 msec of boot time.
> 
> Signed-off-by: Oleksij Rempel <o.rempel at pengutronix.de>
> ---
>  drivers/mci/imx-esdhc.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mci/imx-esdhc.c b/drivers/mci/imx-esdhc.c
> index 141d715c90..5c2a3a36e3 100644
> --- a/drivers/mci/imx-esdhc.c
> +++ b/drivers/mci/imx-esdhc.c
> @@ -95,6 +95,7 @@ struct fsl_esdhc_host {
>  	struct device_d		*dev;
>  	struct clk		*clk;
>  	const struct esdhc_soc_data *socdata;
> +	u32			last_clock;
>  };
>  
>  #define to_fsl_esdhc(mci)	container_of(mci, struct fsl_esdhc_host, mci)
> @@ -408,7 +409,7 @@ esdhc_send_cmd(struct mci_host *mci, struct mci_cmd *cmd, struct mci_data *data)
>  
>  static void set_sysctl(struct mci_host *mci, u32 clock)
>  {
> -	int div, pre_div;
> +	int div, pre_div, i;
>  	struct fsl_esdhc_host *host = to_fsl_esdhc(mci);
>  	void __iomem *regs = host->regs;
>  	int sdhc_clk = clk_get_rate(host->clk);
> @@ -453,13 +454,17 @@ static void set_sysctl(struct mci_host *mci, u32 clock)
>  	esdhc_clrsetbits32(regs + SDHCI_CLOCK_CONTROL__TIMEOUT_CONTROL__SOFTWARE_RESET,
>  			SYSCTL_CLOCK_MASK, clk);
>  
> -	wait_on_timeout(10 * MSECOND,
> -			!(esdhc_read32(regs + SDHCI_PRESENT_STATE) & PRSSTAT_SDSTB));
> +	for (i = 0; i < 1000; i++) {
> +		if (esdhc_read32(regs + SDHCI_PRESENT_STATE) & PRSSTAT_SDSTB)
> +			break;
> +		udelay(10);
> +	}

I hope this hunk doesn't make anything better. If yes, we have a
problem.

>  
>  	clk = SYSCTL_PEREN | SYSCTL_CKEN;
>  
>  	esdhc_setbits32(regs + SDHCI_CLOCK_CONTROL__TIMEOUT_CONTROL__SOFTWARE_RESET,
>  			clk);
> +	host->last_clock = clock;

Instead of storing the desired clock I would rather store the clock we
actually make from the desired clock. This way we could optimze for
multiple input frequencies that result in the same actual frequency.

Also please rename the variable from last_clock to cur_clock.

Sascha


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