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SubjectRe: [PATCH v2 4/4] pinctrl: meson: add support of drive-strength-uA
Hi Guillaume,

On Thu, Apr 18, 2019 at 2:48 PM Guillaume La Roque
<glaroque@baylibre.com> 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@baylibre.com>
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@googlemail.com>

> ---
> 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

> 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

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
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!

[...]
> +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

> + }
>
> 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)

[...]
> +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()?


Regards
Martin

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