[PATCH 6/8] mmc: dw_mmc: Generic MMC tuning with the clock phase framework
Jaehoon Chung
jh80.chung at samsung.com
Tue Sep 15 01:25:38 PDT 2015
Dear, Heiko.
On 09/01/2015 03:24 AM, Heiko Stuebner wrote:
> From: Alexandru M Stan <amstan at 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 at 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 at 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;
>
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