[PATCH v3 1/2] Documentation: mmc: addtional description for post-power-on-delay-ms

[PATCH v3 1/2] Documentation: mmc: addtional description for post-power-on-delay-ms

[Shawn Lin]

post-power-on-delay-ms woule be reused to substitute the hard-coded 10ms
delay waiting for power supply to be stable, specificed by individual
platform/board. Default to 10ms as before, if no available.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>

---

Changes in v3:
- reused post-power-on-delay-ms suggested by Rob

Changes in v2: None

 Documentation/devicetree/bindings/mmc/mmc.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
index 467cd7b..a1d0cf4 100644
--- a/Documentation/devicetree/bindings/mmc/mmc.txt
+++ b/Documentation/devicetree/bindings/mmc/mmc.txt
@@ -56,6 +56,10 @@ Optional properties:
 - fixed-emmc-driver-type: for non-removable eMMC, enforce this driver type.
   The value <n> is the driver type as specified in the eMMC specification
   (table 206 in spec version 5.1).
+- post-power-on-delay-ms : It was invented for MMC pwrseq-simple which could
+  be referred to mmc-pwrseq-simple.txt. But now it's reused as a tunable delay
+  waiting for I/O signalling and card power supply to be stable, regardless of
+  whether pwrseq-simple is used. Default to 10ms if no available.
 
 *NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line
 polarity properties, we have to fix the meaning of the "normal" and "inverted"
-- 
1.9.1

[PATCH v3 2/2] mmc: core: add tunable delay waiting for power to be stable

[Shawn Lin]

The hard-coded 10ms delay in mmc_power_up came from
commit 79bccc5aefb4 ("mmc: increase power up delay"), which said "The TI
controller on Toshiba Tecra M5 needs more time to power up or the cards
will init incorrectly or not at all." But it's too engineering solution
for a special board but force all platforms to wait for that long time,
especially painful for mmc_power_up for eMMC when booting.

However, it's added since 2009, and we can't tell if other platforms
benefit from it. But in practise, the modern hardware are most likely to
have a stable power supply with 1ms after setting it for no matter PMIC
or discrete power. And more importnatly, most regulators implement the
callback of ->set_voltage_time_sel() for regulator core to wait for
specific period of time for the power supply to be stable, which means
once regulator_set_voltage_* return, the power should reach the the
minimum voltage that works for initialization. Of course, if there
are some other ways for host to power the card, we should allow them
to argue a suitable delay as well.

With this patch, we could assign the delay from firmware, or we could
assigne it via ->set_ios() callback from host drivers.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>

---

Changes in v3:
- reuse post-power-on-delay-ms

Changes in v2:
- allow to assign zero delay from firmware suggested by Adrain

 drivers/mmc/core/core.c  | 4 ++--
 drivers/mmc/core/host.c  | 4 ++++
 include/linux/mmc/host.h | 1 +
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 121ce50..a52e9c2 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1658,7 +1658,7 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)
 	 * This delay should be sufficient to allow the power supply
 	 * to reach the minimum voltage.
 	 */
-	mmc_delay(10);
+	mmc_delay(host->ios.power_delay_ms);
 
 	mmc_pwrseq_post_power_on(host);
 
@@ -1671,7 +1671,7 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)
 	 * This delay must be at least 74 clock sizes, or 1 ms, or the
 	 * time required to reach a stable voltage.
 	 */
-	mmc_delay(10);
+	mmc_delay(host->ios.power_delay_ms);
 }
 
 void mmc_power_off(struct mmc_host *host)
diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 64b03d6..b04f239 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c
@@ -338,6 +338,9 @@ int mmc_of_parse(struct mmc_host *host)
 		host->dsr_req = 0;
 	}
 
+	device_property_read_u32(dev, "post-power-on-delay-ms",
+				 &host->ios.power_delay_ms);
+
 	return mmc_pwrseq_alloc(host);
 }
 
@@ -403,6 +406,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
 	host->max_blk_count = PAGE_SIZE / 512;
 
 	host->fixed_drv_type = -EINVAL;
+	host->ios.power_delay_ms = 10;
 
 	return host;
 }
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 7c6eaf6..efa9bab 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -22,6 +22,7 @@
 struct mmc_ios {
 	unsigned int	clock;			/* clock rate */
 	unsigned short	vdd;
+	unsigned int	power_delay_ms;		/* waiting for stable power */
 
 /* vdd stores the bit number of the selected voltage range from below. */
 
-- 
1.9.1

Re: [PATCH v3 1/2] Documentation: mmc: addtional description for post-power-on-delay-ms

[Rob Herring]

On Tue, May 08, 2018 at 09:04:19AM +0800, Shawn Lin wrote:
> post-power-on-delay-ms woule be reused to substitute the hard-coded 10ms
> delay waiting for power supply to be stable, specificed by individual
> platform/board. Default to 10ms as before, if no available.
> 
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
> 
> ---
> 
> Changes in v3:
> - reused post-power-on-delay-ms suggested by Rob
> 
> Changes in v2: None
> 
>  Documentation/devicetree/bindings/mmc/mmc.txt | 4 ++++
>  1 file changed, 4 insertions(+)

Reviewed-by: Rob Herring <robh@kernel.org>

Re: [PATCH v3 1/2] Documentation: mmc: addtional description for post-power-on-delay-ms

[Ulf Hansson]

On 8 May 2018 at 03:04, Shawn Lin <shawn.lin@rock-chips.com> wrote:
> post-power-on-delay-ms woule be reused to substitute the hard-coded 10ms
> delay waiting for power supply to be stable, specificed by individual
> platform/board. Default to 10ms as before, if no available.
>
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>

Thanks, applied for next!

Kind regards
Uffe

>
> ---
>
> Changes in v3:
> - reused post-power-on-delay-ms suggested by Rob
>
> Changes in v2: None
>
>  Documentation/devicetree/bindings/mmc/mmc.txt | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
> index 467cd7b..a1d0cf4 100644
> --- a/Documentation/devicetree/bindings/mmc/mmc.txt
> +++ b/Documentation/devicetree/bindings/mmc/mmc.txt
> @@ -56,6 +56,10 @@ Optional properties:
>  - fixed-emmc-driver-type: for non-removable eMMC, enforce this driver type.
>    The value <n> is the driver type as specified in the eMMC specification
>    (table 206 in spec version 5.1).
> +- post-power-on-delay-ms : It was invented for MMC pwrseq-simple which could
> +  be referred to mmc-pwrseq-simple.txt. But now it's reused as a tunable delay
> +  waiting for I/O signalling and card power supply to be stable, regardless of
> +  whether pwrseq-simple is used. Default to 10ms if no available.
>
>  *NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line
>  polarity properties, we have to fix the meaning of the "normal" and "inverted"
> --
> 1.9.1
>
>

Re: [PATCH v3 2/2] mmc: core: add tunable delay waiting for power to be stable

[Ulf Hansson]

On 8 May 2018 at 03:04, Shawn Lin <shawn.lin@rock-chips.com> wrote:
> The hard-coded 10ms delay in mmc_power_up came from
> commit 79bccc5aefb4 ("mmc: increase power up delay"), which said "The TI
> controller on Toshiba Tecra M5 needs more time to power up or the cards
> will init incorrectly or not at all." But it's too engineering solution
> for a special board but force all platforms to wait for that long time,
> especially painful for mmc_power_up for eMMC when booting.
>
> However, it's added since 2009, and we can't tell if other platforms
> benefit from it. But in practise, the modern hardware are most likely to
> have a stable power supply with 1ms after setting it for no matter PMIC
> or discrete power. And more importnatly, most regulators implement the
> callback of ->set_voltage_time_sel() for regulator core to wait for
> specific period of time for the power supply to be stable, which means
> once regulator_set_voltage_* return, the power should reach the the
> minimum voltage that works for initialization. Of course, if there
> are some other ways for host to power the card, we should allow them
> to argue a suitable delay as well.
>
> With this patch, we could assign the delay from firmware, or we could
> assigne it via ->set_ios() callback from host drivers.
>
> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>

Thanks, applied for next!

Kind regards
Uffe

>
> ---
>
> Changes in v3:
> - reuse post-power-on-delay-ms
>
> Changes in v2:
> - allow to assign zero delay from firmware suggested by Adrain
>
>  drivers/mmc/core/core.c  | 4 ++--
>  drivers/mmc/core/host.c  | 4 ++++
>  include/linux/mmc/host.h | 1 +
>  3 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 121ce50..a52e9c2 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1658,7 +1658,7 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)
>          * This delay should be sufficient to allow the power supply
>          * to reach the minimum voltage.
>          */
> -       mmc_delay(10);
> +       mmc_delay(host->ios.power_delay_ms);
>
>         mmc_pwrseq_post_power_on(host);
>
> @@ -1671,7 +1671,7 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)
>          * This delay must be at least 74 clock sizes, or 1 ms, or the
>          * time required to reach a stable voltage.
>          */
> -       mmc_delay(10);
> +       mmc_delay(host->ios.power_delay_ms);
>  }
>
>  void mmc_power_off(struct mmc_host *host)
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 64b03d6..b04f239 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -338,6 +338,9 @@ int mmc_of_parse(struct mmc_host *host)
>                 host->dsr_req = 0;
>         }
>
> +       device_property_read_u32(dev, "post-power-on-delay-ms",
> +                                &host->ios.power_delay_ms);
> +
>         return mmc_pwrseq_alloc(host);
>  }
>
> @@ -403,6 +406,7 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
>         host->max_blk_count = PAGE_SIZE / 512;
>
>         host->fixed_drv_type = -EINVAL;
> +       host->ios.power_delay_ms = 10;
>
>         return host;
>  }
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 7c6eaf6..efa9bab 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -22,6 +22,7 @@
>  struct mmc_ios {
>         unsigned int    clock;                  /* clock rate */
>         unsigned short  vdd;
> +       unsigned int    power_delay_ms;         /* waiting for stable power */
>
>  /* vdd stores the bit number of the selected voltage range from below. */
>
> --
> 1.9.1
>
>