Re: [PATCH 6/8] mmc: dw_mmc: Generic MMC tuning with the clock phase framework

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

Dear, Heiko.

On 09/01/2015 03:24 AM, Heiko Stuebner wrote:
> From: Alexandru M Stan <amstan@chromium.org>
> 
> This algorithm will try 1 degree increments, since there's no way to tell
> what resolution the underlying phase code uses. As an added bonus, doing
> many tunings yields better results since some tests are run more than once
> (ex: if the underlying driver uses 45 degree increments, the tuning code
> will try the same angle more than once).
> 
> It will then construct a list of good phase ranges (even ranges that cross
> 360/0), will pick the biggest range then it will set the sample_clk to the
> middle of that range.
> 
> We do not touch ciu_drive (and by extension define default-drive-phase).
> Drive phase is mostly used to define minimum hold times, while one could
> write some code to determine what phase meets the minimum hold time (ex 10
> degrees) this will not work with the current clock phase framework (which
> floors angles, so we'll get 0 deg, and there's no way to know what
> resolution the floors happen at). We assume that the default drive angles
> set by the hardware are good enough.
> 
> If a device has device specific code (like exynos) then that will still
> take precedence, otherwise this new code will execute. If the device wants
> to tune, but has no sample_clk defined we'll return EIO with an error
> message.

Which point is "_generic_"? I don't find the code that control the register relevant to CLK_DRV/SMPL PHASE.
It seems that posted the similar patches at u-boot mailing list..

Best Regards,
Jaehoon Chung

> 
> Signed-off-by: Alexandru M Stan <amstan@chromium.org>
> 
> Convert to mmc_send_tuning()
> Fold in from the ChromeOS-tree:
>  - mmc: dw_mmc: Change tuning to only 16 phases
>  - mmc: dw_mmc: Test more phases
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> ---
>  drivers/mmc/host/dw_mmc.c  | 142 +++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mmc/dw_mmc.h |   3 +
>  2 files changed, 145 insertions(+)
> 
> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
> index b1b7e7f..13bcde0 100644
> --- a/drivers/mmc/host/dw_mmc.c
> +++ b/drivers/mmc/host/dw_mmc.c
> @@ -1194,6 +1194,12 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
>  	if (drv_data && drv_data->set_ios)
>  		drv_data->set_ios(slot->host, ios);
>  
> +	/* Make sure we use phases which we can enumerate with */
> +	if (!IS_ERR(slot->host->sample_clk)) {
> +		clk_set_phase(slot->host->sample_clk,
> +			      slot->host->default_sample_phase);
> +	}
> +
>  	switch (ios->power_mode) {
>  	case MMC_POWER_UP:
>  		if (!IS_ERR(mmc->supply.vmmc)) {
> @@ -1414,6 +1420,127 @@ static void dw_mci_enable_sdio_irq(struct mmc_host *mmc, int enb)
>  	spin_unlock_irqrestore(&host->irq_lock, irqflags);
>  }
>  
> +#define NUM_PHASES			360
> +#define TUNING_ITERATION_TO_PHASE(i)	(DIV_ROUND_UP((i) * 360, NUM_PHASES))
> +
> +static int dw_mci_execute_generic_tuning(struct dw_mci_slot *slot)
> +{
> +	struct dw_mci *host = slot->host;
> +	struct mmc_host *mmc = slot->mmc;
> +	int ret = 0;
> +	int i;
> +	bool v, prev_v = 0, first_v;
> +	struct range_t {
> +		int start;
> +		int end; /* inclusive */
> +	};
> +	struct range_t *ranges;
> +	unsigned int range_count = 0;
> +	int longest_range_len = -1;
> +	int longest_range = -1;
> +	int middle_phase;
> +
> +	if (IS_ERR(host->sample_clk)) {
> +		dev_err(host->dev, "Tuning clock (sample_clk) not defined.\n");
> +		return -EIO;
> +	}
> +
> +	ranges = kmalloc_array(NUM_PHASES / 2 + 1, sizeof(*ranges), GFP_KERNEL);
> +	if (!ranges)
> +		return -ENOMEM;
> +
> +	/* Try each phase and extract good ranges */
> +	for (i = 0; i < NUM_PHASES; ) {
> +		clk_set_phase(host->sample_clk, TUNING_ITERATION_TO_PHASE(i));
> +
> +		v = !mmc_send_tuning(mmc);
> +
> +		if (i == 0)
> +			first_v = v;
> +
> +		if ((!prev_v) && v) {
> +			range_count++;
> +			ranges[range_count-1].start = i;
> +		}
> +		if (v) {
> +			ranges[range_count-1].end = i;
> +			i++;
> +		} else if (i == NUM_PHASES - 1) {
> +			/* No extra skipping rules if we're at the end */
> +			i++;
> +		} else {
> +			/*
> +			 * No need to check too close to an invalid
> +			 * one since testing bad phases is slow.  Skip
> +			 * 20 degrees.
> +			 */
> +			i += DIV_ROUND_UP(20 * NUM_PHASES, 360);
> +
> +			/* Always test the last one */
> +			if (i >= NUM_PHASES)
> +				i = NUM_PHASES - 1;
> +		}
> +
> +		prev_v = v;
> +	}
> +
> +	if (range_count == 0) {
> +		dev_warn(host->dev, "All phases bad!");
> +		ret = -EIO;
> +		goto free;
> +	}
> +
> +	/* wrap around case, merge the end points */
> +	if ((range_count > 1) && first_v && v) {
> +		ranges[0].start = ranges[range_count-1].start;
> +		range_count--;
> +	}
> +
> +	if (ranges[0].start == 0 && ranges[0].end == NUM_PHASES - 1) {
> +		clk_set_phase(host->sample_clk, host->default_sample_phase);
> +		dev_info(host->dev, "All phases work, using default phase %d.",
> +			 host->default_sample_phase);
> +		goto free;
> +	}
> +
> +	/* Find the longest range */
> +	for (i = 0; i < range_count; i++) {
> +		int len = (ranges[i].end - ranges[i].start + 1);
> +
> +		if (len < 0)
> +			len += NUM_PHASES;
> +
> +		if (longest_range_len < len) {
> +			longest_range_len = len;
> +			longest_range = i;
> +		}
> +
> +		dev_dbg(host->dev, "Good phase range %d-%d (%d len)\n",
> +			TUNING_ITERATION_TO_PHASE(ranges[i].start),
> +			TUNING_ITERATION_TO_PHASE(ranges[i].end),
> +			len
> +		);
> +	}
> +
> +	dev_dbg(host->dev, "Best phase range %d-%d (%d len)\n",
> +		TUNING_ITERATION_TO_PHASE(ranges[longest_range].start),
> +		TUNING_ITERATION_TO_PHASE(ranges[longest_range].end),
> +		longest_range_len
> +	);
> +
> +	middle_phase = ranges[longest_range].start + longest_range_len / 2;
> +	middle_phase %= NUM_PHASES;
> +	dev_info(host->dev, "Successfully tuned phase to %d\n",
> +		 TUNING_ITERATION_TO_PHASE(middle_phase));
> +
> +	clk_set_phase(host->sample_clk,
> +		      TUNING_ITERATION_TO_PHASE(middle_phase));
> +
> +free:
> +	kfree(ranges);
> +	return ret;
> +}
> +
>  static int dw_mci_execute_tuning(struct mmc_host *mmc, u32 opcode)
>  {
>  	struct dw_mci_slot *slot = mmc_priv(mmc);
> @@ -1423,6 +1550,8 @@ static int dw_mci_execute_tuning(struct mmc_host *mmc, u32 opcode)
>  
>  	if (drv_data && drv_data->execute_tuning)
>  		err = drv_data->execute_tuning(slot);
> +	else
> +		err = dw_mci_execute_generic_tuning(slot);
>  	return err;
>  }
>  
> @@ -2741,6 +2870,11 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
>  	if (!of_property_read_u32(np, "clock-frequency", &clock_frequency))
>  		pdata->bus_hz = clock_frequency;
>  
> +	if (of_property_read_u32(np, "default-sample-phase",
> +					&host->default_sample_phase)) {
> +		host->default_sample_phase = 0;
> +	}
> +
>  	if (drv_data && drv_data->parse_dt) {
>  		ret = drv_data->parse_dt(host);
>  		if (ret)
> @@ -2843,6 +2977,14 @@ int dw_mci_probe(struct dw_mci *host)
>  		host->bus_hz = clk_get_rate(host->ciu_clk);
>  	}
>  
> +	host->drv_clk = devm_clk_get(host->dev, "ciu_drv");
> +	if (IS_ERR(host->drv_clk))
> +		dev_dbg(host->dev, "ciu_drv not available\n");
> +
> +	host->sample_clk = devm_clk_get(host->dev, "ciu_sample");
> +	if (IS_ERR(host->sample_clk))
> +		dev_dbg(host->dev, "ciu_sample not available\n");
> +
>  	if (!host->bus_hz) {
>  		dev_err(host->dev,
>  			"Platform data must supply bus speed\n");
> diff --git a/include/linux/mmc/dw_mmc.h b/include/linux/mmc/dw_mmc.h
> index 134c574..40187ba 100644
> --- a/include/linux/mmc/dw_mmc.h
> +++ b/include/linux/mmc/dw_mmc.h
> @@ -176,7 +176,10 @@ struct dw_mci {
>  	void			*priv;
>  	struct clk		*biu_clk;
>  	struct clk		*ciu_clk;
> +	struct clk		*drv_clk;
> +	struct clk		*sample_clk;
>  	struct dw_mci_slot	*slot[MAX_MCI_SLOTS];
> +	int			default_sample_phase;
>  
>  	/* FIFO push and pull */
>  	int			fifo_depth;
>