Re: [PATCH] regulator: s2mps11: Fix invalid minimal selector for buck9 supplying SD card

[Javier Martinez Canillas <javier@osg.samsung.com>]

Hello Krzysztof,

On 03/27/2016 08:54 PM, Krzysztof Kozlowski wrote:
> The buck9 regulator of S2MPS11 PMIC lacked minimal selector for linear
> mapping. The mapping starts from 0x40 (3 V).
>

This patch is a real fix since the the SD error goes away and the regulator
driver probes correctly now.
 
> This buck9 provides power to other regulators, including LDO13 and LDO19
> which supply the MMC2 (SD card).
>

I think it's worth mentioning that this is the case for the Exynos5422 Odroid
XU{3,4} boards. I mean, the regulators can be used for anything but are those
boards that use LDO19 as the SD card supply.

In fact, I wonder if the subject line shouldn't be changed to something like:

"regulator: s2mps11: Fix invalid min selector and voltages num for buck9"

since the real problem is that the .linear_min_sel and .n_voltages are wrong.
The fact that the SD was failing on Odroids is just a consequence of that
(although I agree that this information should be part of the commit message).

> Bootloader initializes the regulator with value of 0xff (5 V) which is
> outside of supported voltage range. When (during boot) constraints to
> buck9 were applied, the driver wrote value counting from 0x00, not 0x40.
> Effectively driver set lower voltage than required leading to SD card
> detection errors on Odroid XU3/XU4:
> 	mmc1: card never left busy state
> 	mmc1: error -110 whilst initialising SD card
> 
> Fixes: cb74685ecb39 ("regulator: s2mps11: Add samsung s2mps11 regulator driver")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> 
> ---
> 
> The issue can be reproduced on next-20160324 with
> bae4fdc88d7f7dda1 (regulator: core: Ensure we are at least in bounds
> for our constraints).
> ---
>  drivers/regulator/s2mps11.c         | 19 ++++++++++++++++++-
>  include/linux/mfd/samsung/s2mps11.h |  9 +++++++++
>  2 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/regulator/s2mps11.c b/drivers/regulator/s2mps11.c
> index d24e2c783dc5..caeefc38ac47 100644
> --- a/drivers/regulator/s2mps11.c
> +++ b/drivers/regulator/s2mps11.c
> @@ -324,6 +324,23 @@ static struct regulator_ops s2mps11_buck_ops = {
>  	.enable_mask	= S2MPS11_ENABLE_MASK			\
>  }
>  
> +#define regulator_desc_s2mps11_buck9 {				\
> +	.name		= "BUCK9",				\
> +	.id		= S2MPS11_BUCK9,			\
> +	.ops		= &s2mps11_buck_ops,			\
> +	.type		= REGULATOR_VOLTAGE,			\
> +	.owner		= THIS_MODULE,				\
> +	.min_uV		= MIN_3000_MV,				\
> +	.uV_step	= STEP_25_MV,				\
> +	.linear_min_sel	= S2MPS11_BUCK9_MIN_VSEL,		\

I don't have a datasheet for this PMIC but I wonder if buck9 is the only
buck regulator whose minimal register value is != 0. If that's not the
case, it would be good to fix the descriptions for all other regulators.

> +	.n_voltages	= S2MPS11_BUCK9_N_VOLTAGES,		\
> +	.ramp_delay	= S2MPS11_RAMP_DELAY,			\
> +	.vsel_reg	= S2MPS11_REG_B9CTRL2,			\
> +	.vsel_mask	= S2MPS11_BUCK_VSEL_MASK,		\
> +	.enable_reg	= S2MPS11_REG_B9CTRL1,			\
> +	.enable_mask	= S2MPS11_ENABLE_MASK			\
> +}
> +
>  static const struct regulator_desc s2mps11_regulators[] = {
>  	regulator_desc_s2mps11_ldo(1, STEP_25_MV),
>  	regulator_desc_s2mps11_ldo(2, STEP_50_MV),
> @@ -371,7 +388,7 @@ static const struct regulator_desc s2mps11_regulators[] = {
>  	regulator_desc_s2mps11_buck6_10(6, MIN_600_MV, STEP_6_25_MV),
>  	regulator_desc_s2mps11_buck6_10(7, MIN_600_MV, STEP_6_25_MV),
>  	regulator_desc_s2mps11_buck6_10(8, MIN_600_MV, STEP_6_25_MV),
> -	regulator_desc_s2mps11_buck6_10(9, MIN_3000_MV, STEP_25_MV),

Maybe the regulator_desc_s2mps11_buck6_10() define should be renamed?
Since it's no longer true that can be used for buck6-10, so the name
is misleading now.

Patch looks good to me though and as I said it fixes the issue so:

Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America