linux-kernel - Re: [PATCH -next] mfd: ntxec: Support for EC in Tolino Shine 2 HD

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Message-ID: <YEPUppNWNiAMnczF@latitude>
Date:   Sat, 6 Mar 2021 20:14:46 +0100
From:   Jonathan Neuschäfer <j.neuschaefer@....net>
To:     Andreas Kemnade <andreas@...nade.info>
Cc:     j.neuschaefer@....net, lee.jones@...aro.org,
        linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH -next] mfd: ntxec: Support for EC in Tolino Shine 2 HD

Hi,

(Cc'ing Mark Brown because of the regmap related questions)

On Sat, Mar 06, 2021 at 07:13:14PM +0100, Andreas Kemnade wrote:
> Add the version of the EC in the Tolino Shine 2 HD
> to the supported versions. It seems not to have an RTC
> and does not ack data written to it.
> The vendor kernel happily ignores write errors, using
> I2C via userspace i2c-set also shows the error.
> So add a quirk to ignore that error.
> 
> PWM can be successfully configured despite of that error.

I'm curious, is this one of the variants with two PWM channels
(for configurable color temperature)?

> 
> Signed-off-by: Andreas Kemnade <andreas@...nade.info>
> ---
>  drivers/mfd/ntxec.c       | 57 ++++++++++++++++++++++++++++++++++++---
>  include/linux/mfd/ntxec.h |  1 +
>  2 files changed, 55 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c
> index 957de2b03529..e7fe570127af 100644
> --- a/drivers/mfd/ntxec.c
> +++ b/drivers/mfd/ntxec.c
> @@ -96,6 +96,36 @@ static struct notifier_block ntxec_restart_handler = {
>  	.priority = 128,
>  };
>  
> +static int regmap_ignore_write(void *context,
> +			       unsigned int reg, unsigned int val)
> +
> +{
> +	struct regmap *regmap = context;
> +
> +	regmap_write(regmap, reg, val);
> +
> +	return 0;
> +}
> +
> +static int regmap_wrap_read(void *context, unsigned int reg,
> +			    unsigned int *val)
> +{
> +	struct regmap *regmap = context;
> +
> +	return regmap_read(regmap, reg, val);
> +}
> +
> +/* some firmware versions do not ack written data, add a wrapper */
> +static const struct regmap_config regmap_config_noack = {
> +	.name = "ntxec_noack",
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.cache_type = REGCACHE_NONE,
> +	.val_format_endian = REGMAP_ENDIAN_BIG,
> +	.reg_write = regmap_ignore_write,
> +	.reg_read = regmap_wrap_read

Is the read wrapper necessary? It seems to me from reading regmap.h
that leaving .reg_read set to NULL should do the right thing, but I'm
not sure.

> +};
> +
>  static const struct regmap_config regmap_config = {
>  	.name = "ntxec",
>  	.reg_bits = 8,
> @@ -109,10 +139,15 @@ static const struct mfd_cell ntxec_subdevices[] = {
>  	{ .name = "ntxec-pwm" },
>  };
>  
> +static const struct mfd_cell ntxec_subdev_pwm[] = {
> +	{ .name = "ntxec-pwm" },
> +};

ntxec_subdevices vs. ntxec_subdev_pwm seems slightly inconsistent in
naming. ntxec_subdevices_pwm would be a wrong plural, but IMHO slightly
better because of consistency. Maybe rename ntxec_subdevices to
ntxec_subdev?

> +
>  static int ntxec_probe(struct i2c_client *client)
>  {
>  	struct ntxec *ec;
>  	unsigned int version;
> +	bool has_rtc;
>  	int res;
>  
>  	ec = devm_kmalloc(&client->dev, sizeof(*ec), GFP_KERNEL);
> @@ -137,6 +172,15 @@ static int ntxec_probe(struct i2c_client *client)
>  	/* Bail out if we encounter an unknown firmware version */
>  	switch (version) {
>  	case NTXEC_VERSION_KOBO_AURA:
> +		has_rtc = true;
> +		break;
> +	case NTXEC_VERSION_TOLINO_SHINE2:
> +		has_rtc = false;
> +		ec->regmap = devm_regmap_init(ec->dev, NULL,
> +					      ec->regmap,
> +					      &regmap_config_noack);

Ah— A custom regmap stacked on top of the old regmap… I think this
deserves a comment.

> +		if (IS_ERR(ec->regmap))
> +			return PTR_ERR(ec->regmap);
>  		break;
>  	default:
>  		dev_err(ec->dev,
> @@ -155,7 +199,6 @@ static int ntxec_probe(struct i2c_client *client)
>  		 */
>  		res = regmap_write(ec->regmap, NTXEC_REG_POWERKEEP,
>  				   NTXEC_POWERKEEP_VALUE);
> -		if (res < 0)
>  			return res;

This deletion looks like a mistake.

>  
>  		if (poweroff_restart_client)
> @@ -181,8 +224,16 @@ static int ntxec_probe(struct i2c_client *client)
>  
>  	i2c_set_clientdata(client, ec);
>  
> -	res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE, ntxec_subdevices,
> -				   ARRAY_SIZE(ntxec_subdevices), NULL, 0, NULL);
> +	if (has_rtc)
> +		res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE,
> +					   ntxec_subdevices,
> +					   ARRAY_SIZE(ntxec_subdevices),
> +					   NULL, 0, NULL);
> +	else
> +		res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE,
> +					   ntxec_subdev_pwm,
> +					   ARRAY_SIZE(ntxec_subdev_pwm),
> +					   NULL, 0, NULL);

At some point, it will probably be simpler to have

	struct mfd_cell *subdev = ntxec_subdevices;
	size_t subdev_size = ARRAY_SIZE(ntxec_subdevices);

on top of the probe function and override them in the switch statement,
but at this point I think it doesn't matter, and either way is fine.

>  	if (res)
>  		dev_err(ec->dev, "Failed to add subdevices: %d\n", res);
>  
> diff --git a/include/linux/mfd/ntxec.h b/include/linux/mfd/ntxec.h
> index 361204d125f1..26ab3b8eb612 100644
> --- a/include/linux/mfd/ntxec.h
> +++ b/include/linux/mfd/ntxec.h
> @@ -33,5 +33,6 @@ static inline __be16 ntxec_reg8(u8 value)
>  
>  /* Known firmware versions */
>  #define NTXEC_VERSION_KOBO_AURA	0xd726	/* found in Kobo Aura */
> +#define NTXEC_VERSION_TOLINO_SHINE2 0xf110 /* found in Tolino Shine 2 HD */
>  
>  #endif
> -- 
> 2.29.2
> 


Thanks for your patch,
Jonathan

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