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

Message ID 1441045446-30858-7-git-send-email-heiko@sntech.de
State New
Headers show

Commit Message

Heiko Stuebner Aug. 31, 2015, 6:24 p.m. UTC
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.

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(+)

Comments

Jaehoon Chung Sept. 15, 2015, 8:25 a.m. UTC | #1
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;
>
Heiko Stuebner Sept. 15, 2015, 10:09 p.m. UTC | #2
Hi,

Am Dienstag, 15. September 2015, 17:25:38 schrieb Jaehoon Chung:
> 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..

The "generic" part is that it uses the clk phase API for dw_mmc 
implementations where the clkgen controlling interface is outside the dw_mmc 
IP itself. So it's open for other implementations as well.

But if you are more comfortable with it, I can also move it into the dw_mmc-
rockchip variant for the time being, until another user comes along.


Heiko
Jaehoon Chung Sept. 16, 2015, 2:30 a.m. UTC | #3
Hi,

On 09/16/2015 07:09 AM, Heiko Stübner wrote:
> Hi,
> 
> Am Dienstag, 15. September 2015, 17:25:38 schrieb Jaehoon Chung:
>> 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..
> 
> The "generic" part is that it uses the clk phase API for dw_mmc 
> implementations where the clkgen controlling interface is outside the dw_mmc 
> IP itself. So it's open for other implementations as well.

Designware IP also has the CLK phase register(UHS_REG_EXT register)...
if this code is related with it, it should be located into dw-mmc.c.

> 
> But if you are more comfortable with it, I can also move it into the dw_mmc-
> rockchip variant for the time being, until another user comes along.

I think more better that this code is located into dw_mmc-rockchip. how about?

Best Regards,
Jaehoon Chung

> 
> 
> Heiko
> 
>
Heiko Stuebner Sept. 16, 2015, 2:52 p.m. UTC | #4
Hi,

Am Mittwoch, 16. September 2015, 11:30:26 schrieb Jaehoon Chung:
> On 09/16/2015 07:09 AM, Heiko Stübner wrote:
> > Am Dienstag, 15. September 2015, 17:25:38 schrieb Jaehoon Chung:
> >> 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..
> > 
> > The "generic" part is that it uses the clk phase API for dw_mmc
> > implementations where the clkgen controlling interface is outside the
> > dw_mmc IP itself. So it's open for other implementations as well.
> 
> Designware IP also has the CLK phase register(UHS_REG_EXT register)...
> if this code is related with it, it should be located into dw-mmc.c.

UHS_REG_EXT is acutally "reserved" on both the rk3288 as well as the rk3368. 
rk3036/rk3128 (Cortex-A7) provide a bit description, but the tuning 
documentation still uses the controls located in the clock controller.

So I guess UHS_REG_EXT is the real "generic" solution.

> > But if you are more comfortable with it, I can also move it into the
> > dw_mmc- rockchip variant for the time being, until another user comes
> > along.
> I think more better that this code is located into dw_mmc-rockchip. how
> about?

As described above, moving that to the rockchip part sounds sensible. And I 
guess we can think more about it, once a second user appears.


Heiko
Jaehoon Chung Sept. 17, 2015, 2:03 a.m. UTC | #5
Hi,

On 09/16/2015 11:52 PM, Heiko Stübner wrote:
> Hi,
> 
> Am Mittwoch, 16. September 2015, 11:30:26 schrieb Jaehoon Chung:
>> On 09/16/2015 07:09 AM, Heiko Stübner wrote:
>>> Am Dienstag, 15. September 2015, 17:25:38 schrieb Jaehoon Chung:
>>>> 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..
>>>
>>> The "generic" part is that it uses the clk phase API for dw_mmc
>>> implementations where the clkgen controlling interface is outside the
>>> dw_mmc IP itself. So it's open for other implementations as well.
>>
>> Designware IP also has the CLK phase register(UHS_REG_EXT register)...
>> if this code is related with it, it should be located into dw-mmc.c.
> 
> UHS_REG_EXT is acutally "reserved" on both the rk3288 as well as the rk3368. 
> rk3036/rk3128 (Cortex-A7) provide a bit description, but the tuning 
> documentation still uses the controls located in the clock controller.
> 
> So I guess UHS_REG_EXT is the real "generic" solution.
> 
>>> But if you are more comfortable with it, I can also move it into the
>>> dw_mmc- rockchip variant for the time being, until another user comes
>>> along.
>> I think more better that this code is located into dw_mmc-rockchip. how
>> about?
> 
> As described above, moving that to the rockchip part sounds sensible. And I 
> guess we can think more about it, once a second user appears.

Sure, we can think more about this.
As you knew, clock phase is closely related to the timing issue.
So clock phase scheme needs to control however.
In future, if somebody introduce the similar control as rockchip, we can discuss about it.

Best Regards,
Jaehoon Chung

> 
> 
> Heiko
>

Patch
diff mbox

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;