Re: [PATCH v2 4/4] pinctrl: meson: add support of drive-strength-uA

From: guillaume La Roque
Date: Tue Apr 30 2019 - 03:20:47 EST

Hi Martin,


thanks for your feedback.


On 4/27/19 9:44 PM, Martin Blumenstingl wrote:
> Hi Guillaume,
>
> On Thu, Apr 18, 2019 at 2:48 PM Guillaume La Roque
> <glaroque@xxxxxxxxxxxx> wrote:
>> drive-strength-uA is a new feature needed for G12A SoC.
>> the default DS setting after boot is usually 500uA and it is not enough for
>> many functions. We need to be able to set the drive strength to reliably
>> enable things like MMC, I2C, etc ...
>>
>> Signed-off-by: Guillaume La Roque <glaroque@xxxxxxxxxxxx>
> I gave this a go on Meson8m2 (meaning I applied all four patches from
> this series and booted the result on my board):
> [Meson8m2 doesn't support drive strength and still boots without any
> crashes or obvious regressions]
> Tested-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
>
>> ---
>> drivers/pinctrl/meson/pinctrl-meson-g12a.c | 36 ++---
>> drivers/pinctrl/meson/pinctrl-meson.c | 166 ++++++++++++++++-----
>> drivers/pinctrl/meson/pinctrl-meson.h | 20 ++-
> personally I would have split this into two separate patches:
> - one for the generic pinctrl-meson part which adds drive-strength-uA support
> - another patch for enabling this on G12A
>
> if nobody else wants you to split this then it's fine for me as well


why not if i send new series i will do.


>
>> 3 files changed, 163 insertions(+), 59 deletions(-)
>>
>> diff --git a/drivers/pinctrl/meson/pinctrl-meson-g12a.c b/drivers/pinctrl/meson/pinctrl-meson-g12a.c
>> index d494492e98e9..3475cd7bd2af 100644
>> --- a/drivers/pinctrl/meson/pinctrl-meson-g12a.c
>> +++ b/drivers/pinctrl/meson/pinctrl-meson-g12a.c
>> @@ -1304,28 +1304,28 @@ static struct meson_pmx_func meson_g12a_aobus_functions[] = {
>> };
>>
>> static struct meson_bank meson_g12a_periphs_banks[] = {
>> - /* name first last irq pullen pull dir out in */
>> - BANK("Z", GPIOZ_0, GPIOZ_15, 12, 27,
>> - 4, 0, 4, 0, 12, 0, 13, 0, 14, 0),
>> - BANK("H", GPIOH_0, GPIOH_8, 28, 36,
>> - 3, 0, 3, 0, 9, 0, 10, 0, 11, 0),
>> - BANK("BOOT", BOOT_0, BOOT_15, 37, 52,
>> - 0, 0, 0, 0, 0, 0, 1, 0, 2, 0),
>> - BANK("C", GPIOC_0, GPIOC_7, 53, 60,
>> - 1, 0, 1, 0, 3, 0, 4, 0, 5, 0),
>> - BANK("A", GPIOA_0, GPIOA_15, 61, 76,
>> - 5, 0, 5, 0, 16, 0, 17, 0, 18, 0),
>> - BANK("X", GPIOX_0, GPIOX_19, 77, 96,
>> - 2, 0, 2, 0, 6, 0, 7, 0, 8, 0),
>> + /* name first last irq pullen pull dir out in ds */
>> + BANK_DS("Z", GPIOZ_0, GPIOZ_15, 12, 27,
>> + 4, 0, 4, 0, 12, 0, 13, 0, 14, 0, 5, 0),
>> + BANK_DS("H", GPIOH_0, GPIOH_8, 28, 36,
>> + 3, 0, 3, 0, 9, 0, 10, 0, 11, 0, 4, 0),
>> + BANK_DS("BOOT", BOOT_0, BOOT_15, 37, 52,
>> + 0, 0, 0, 0, 0, 0, 1, 0, 2, 0, 0, 0),
>> + BANK_DS("C", GPIOC_0, GPIOC_7, 53, 60,
>> + 1, 0, 1, 0, 3, 0, 4, 0, 5, 0, 1, 0),
>> + BANK_DS("A", GPIOA_0, GPIOA_15, 61, 76,
>> + 5, 0, 5, 0, 16, 0, 17, 0, 18, 0, 6, 0),
>> + BANK_DS("X", GPIOX_0, GPIOX_19, 77, 96,
>> + 2, 0, 2, 0, 6, 0, 7, 0, 8, 0, 2, 0),
>> };
>>
>> static struct meson_bank meson_g12a_aobus_banks[] = {
>> - /* name first last irq pullen pull dir out in */
>> - BANK("AO", GPIOAO_0, GPIOAO_11, 0, 11,
>> - 3, 0, 2, 0, 0, 0, 4, 0, 1, 0),
>> + /* name first last irq pullen pull dir out in ds */
>> + BANK_DS("AO", GPIOAO_0, GPIOAO_11, 0, 11, 3, 0, 2, 0, 0, 0, 4, 0, 1, 0,
>> + 0, 0),
>> /* GPIOE actually located in the AO bank */
>> - BANK("E", GPIOE_0, GPIOE_2, 97, 99,
>> - 3, 16, 2, 16, 0, 16, 4, 16, 1, 16),
>> + BANK_DS("E", GPIOE_0, GPIOE_2, 97, 99, 3, 16, 2, 16, 0, 16, 4, 16, 1,
>> + 16, 1, 0),
>> };
> these definitions are really hard to read, but it's been like this
> even before your patch
>
>> static struct meson_pmx_bank meson_g12a_periphs_pmx_banks[] = {
>> diff --git a/drivers/pinctrl/meson/pinctrl-meson.c b/drivers/pinctrl/meson/pinctrl-meson.c
>> index 96a4a72708e4..5108e5aa6514 100644
>> --- a/drivers/pinctrl/meson/pinctrl-meson.c
>> +++ b/drivers/pinctrl/meson/pinctrl-meson.c
>> @@ -174,62 +174,106 @@ int meson_pmx_get_groups(struct pinctrl_dev *pcdev, unsigned selector,
>> return 0;
>> }
>>
>> -static int meson_pinconf_set(struct pinctrl_dev *pcdev, unsigned int pin,
>> - unsigned long *configs, unsigned num_configs)
>> +static int meson_pinconf_set_bias(struct meson_pinctrl *pc, unsigned int pin,
>> + enum pin_config_param conf)
> can you please confirm that I understood the purpose of this correctly:
> I think you introduce this to make setting the bias consistent with
> how you set the drive-strength.
> if so then it would be great to have a separate patch which describes
> that it's only a code-style change and a functional no-op


you are right, i will separate this changes.


>
> additionally the function arguments are not consistent with
> meson_pinconf_get_drive_strength():
> - here you pass the pinctrl subsystem specific parameters (enum
> pin_config_param conf)
> - in meson_pinconf_get_drive_strength the conversion for pinctrl
> subsystem specific values (pinconf_to_config_argument) is part of
> meson_pinconf_set


for param i'm not sure i understand what you want, if you talk about difference between set_bias and set_drive arg , it's difficult to align it.

if it's about diff between get_bias and get_drive i think i can return drive stength value instead of using an u16 arg input param.


> I'm wondering whether two separate functions
> (meson_pinconf_disable_bias and meson_pinconf_enable_bias) would make
> things easier to read. I haven't tried whether this would really make
> things better, so I'd like to hear your opinion on this Guillaume!


no special opinion on this, if you think it's better for understanding i can separate set_bias function.


>
> [...]
>> +static int meson_pinconf_set_drive_strength(struct meson_pinctrl *pc,
>> + unsigned int pin, u16 arg)
>> {
>> - struct meson_pinctrl *pc = pinctrl_dev_get_drvdata(pcdev);
>> struct meson_bank *bank;
>> - enum pin_config_param param;
>> unsigned int reg, bit;
>> - int i, ret;
>> + unsigned int ds_val;
>> + int ret;
>> +
>> + if (!pc->reg_ds) {
>> + dev_err(pc->dev, "drive-strength not supported\n");
>> + return -ENOTSUPP;
> in meson_pinconf_set() we don't complain (with a dev_err) for this case.
> I'm not sure what the best-practice is for the pinctrl subsystem,
> maybe Linus can comment on this
>

this check is to be sure it's possible to set drive stength,

if no register bank is setting in DT but drive-stength properties are setting on pins i need to generate an error

because something is wrong.


>> + }
>>
>> ret = meson_get_bank(pc, pin, &bank);
>> if (ret)
>> return ret;
>>
>> + meson_calc_reg_and_bit(bank, pin, REG_DS, &reg, &bit);
>> + bit = bit << 1;
>> +
>> + if (arg <= 500) {
>> + ds_val = MESON_PINCONF_DRV_500UA;
>> + } else if (arg <= 2500) {
>> + ds_val = MESON_PINCONF_DRV_2500UA;
>> + } else if (arg <= 3000) {
>> + ds_val = MESON_PINCONF_DRV_3000UA;
>> + } else if (arg <= 4000) {
>> + ds_val = MESON_PINCONF_DRV_4000UA;
>> + } else {
>> + dev_warn_once(pc->dev,
>> + "pin %u: invalid drive-strength : %d , default to 4mA\n",
>> + pin, arg);
>> + ds_val = MESON_PINCONF_DRV_4000UA;
> why not return -EINVAL here? (my assumption is that the pinctrl
> subsystem would like to have -EINVAL instead of drivers doing
> fallbacks if the values are out-of-range, but I'm not 100% sure about
> this)
>
> [...]


i choose to set a default value instead of generating an error,

in this case it's only if you ask a value upper than 4000uA so it's not really a risk to set 4000uA by default.


>> +static int meson_pinconf_get_drive_strength(struct meson_pinctrl *pc,
>> + unsigned int pin, u16 *arg)
>> +{
>> + struct meson_bank *bank;
>> + unsigned int reg, bit;
>> + unsigned int val;
>> + int ret;
>> +
> do you need to return -ENOTSUPP here if pc->reg_ds is NULL, similar to
> what you already have in meson_pinconf_set_drive_strength()?

depending of linux comment on your feedback on meson_pinconf_set_drive_strength

i will update this part .


>
>
> Regards
> Martin


Regards

Guillaume