linux-kernel - Re: [PATCH 2/3] pinctrl: at91-pio4: add support for slew-rate

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Message-ID: <20210127095629.ahfp6llqjzhhafyd@sekiro>
Date:   Wed, 27 Jan 2021 10:56:29 +0100
From:   Ludovic Desroches <ludovic.desroches@...rochip.com>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>
CC:     <linus.walleij@...aro.org>, <robh+dt@...nel.org>,
        <nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <linux-gpio@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] pinctrl: at91-pio4: add support for slew-rate

On Mon, Jan 25, 2021 at 12:19:13PM +0200, Claudiu Beznea wrote:
> SAMA7G5 supports slew rate configuration. Adapt the driver for this.
> For switching frequencies lower than 50MHz the slew rate needs to
> be enabled. Since most of the pins on SAMA7G5 fall into this category
> enabled the slew rate by default.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> ---
>  drivers/pinctrl/pinctrl-at91-pio4.c | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/drivers/pinctrl/pinctrl-at91-pio4.c b/drivers/pinctrl/pinctrl-at91-pio4.c
> index d267367d94b9..c59ab0bfb945 100644
> --- a/drivers/pinctrl/pinctrl-at91-pio4.c
> +++ b/drivers/pinctrl/pinctrl-at91-pio4.c
> @@ -36,6 +36,7 @@
>  #define		ATMEL_PIO_DIR_MASK		BIT(8)
>  #define		ATMEL_PIO_PUEN_MASK		BIT(9)
>  #define		ATMEL_PIO_PDEN_MASK		BIT(10)
> +#define		ATMEL_PIO_SR_MASK		BIT(11)
>  #define		ATMEL_PIO_IFEN_MASK		BIT(12)
>  #define		ATMEL_PIO_IFSCEN_MASK		BIT(13)
>  #define		ATMEL_PIO_OPD_MASK		BIT(14)
> @@ -76,10 +77,12 @@
>   * @nbanks: number of PIO banks
>   * @last_bank_count: number of lines in the last bank (can be less than
>   *	the rest of the banks).
> + * @sr: slew rate support
>   */
>  struct atmel_pioctrl_data {
>  	unsigned nbanks;
>  	unsigned last_bank_count;
> +	unsigned int sr;

Hi Claudiu,

Nitpicking: I tend to prefer a verbose name as slew_rate or even
slew_rate_support.

Otherwise,
Acked-by: Ludovic Desroches <ludovic.desroches@...rochip.com>

Regards

Ludovic

>  };
>  
>  struct atmel_group {
> @@ -117,6 +120,7 @@ struct atmel_pin {
>   * @pm_suspend_backup: backup/restore register values on suspend/resume
>   * @dev: device entry for the Atmel PIO controller.
>   * @node: node of the Atmel PIO controller.
> + * @sr: slew rate support
>   */
>  struct atmel_pioctrl {
>  	void __iomem		*reg_base;
> @@ -138,6 +142,7 @@ struct atmel_pioctrl {
>  	} *pm_suspend_backup;
>  	struct device		*dev;
>  	struct device_node	*node;
> +	unsigned int		sr;
>  };
>  
>  static const char * const atmel_functions[] = {
> @@ -760,6 +765,13 @@ static int atmel_conf_pin_config_group_get(struct pinctrl_dev *pctldev,
>  			return -EINVAL;
>  		arg = 1;
>  		break;
> +	case PIN_CONFIG_SLEW_RATE:
> +		if (!atmel_pioctrl->sr)
> +			return -EOPNOTSUPP;
> +		if (!(res & ATMEL_PIO_SR_MASK))
> +			return -EINVAL;
> +		arg = 1;
> +		break;
>  	case ATMEL_PIN_CONFIG_DRIVE_STRENGTH:
>  		if (!(res & ATMEL_PIO_DRVSTR_MASK))
>  			return -EINVAL;
> @@ -793,6 +805,10 @@ static int atmel_conf_pin_config_group_set(struct pinctrl_dev *pctldev,
>  		dev_dbg(pctldev->dev, "%s: pin=%u, config=0x%lx\n",
>  			__func__, pin_id, configs[i]);
>  
> +		/* Keep slew rate enabled by default. */
> +		if (atmel_pioctrl->sr)
> +			conf |= ATMEL_PIO_SR_MASK;
> +
>  		switch (param) {
>  		case PIN_CONFIG_BIAS_DISABLE:
>  			conf &= (~ATMEL_PIO_PUEN_MASK);
> @@ -850,6 +866,13 @@ static int atmel_conf_pin_config_group_set(struct pinctrl_dev *pctldev,
>  					ATMEL_PIO_SODR);
>  			}
>  			break;
> +		case PIN_CONFIG_SLEW_RATE:
> +			if (!atmel_pioctrl->sr)
> +				break;
> +			/* And remove it if explicitly requested. */
> +			if (arg == 0)
> +				conf &= ~ATMEL_PIO_SR_MASK;
> +			break;
>  		case ATMEL_PIN_CONFIG_DRIVE_STRENGTH:
>  			switch (arg) {
>  			case ATMEL_PIO_DRVSTR_LO:
> @@ -901,6 +924,8 @@ static void atmel_conf_pin_config_dbg_show(struct pinctrl_dev *pctldev,
>  		seq_printf(s, "%s ", "open-drain");
>  	if (conf & ATMEL_PIO_SCHMITT_MASK)
>  		seq_printf(s, "%s ", "schmitt");
> +	if (atmel_pioctrl->sr && (conf & ATMEL_PIO_SR_MASK))
> +		seq_printf(s, "%s ", "slew-rate");
>  	if (conf & ATMEL_PIO_DRVSTR_MASK) {
>  		switch ((conf & ATMEL_PIO_DRVSTR_MASK) >> ATMEL_PIO_DRVSTR_OFFSET) {
>  		case ATMEL_PIO_DRVSTR_ME:
> @@ -994,6 +1019,7 @@ static const struct atmel_pioctrl_data atmel_sama5d2_pioctrl_data = {
>  static const struct atmel_pioctrl_data microchip_sama7g5_pioctrl_data = {
>  	.nbanks			= 5,
>  	.last_bank_count	= 8, /* sama7g5 has only PE0 to PE7 */
> +	.sr			= 1,
>  };
>  
>  static const struct of_device_id atmel_pctrl_of_match[] = {
> @@ -1039,6 +1065,7 @@ static int atmel_pinctrl_probe(struct platform_device *pdev)
>  		atmel_pioctrl->npins -= ATMEL_PIO_NPINS_PER_BANK;
>  		atmel_pioctrl->npins += atmel_pioctrl_data->last_bank_count;
>  	}
> +	atmel_pioctrl->sr = atmel_pioctrl_data->sr;
>  
>  	atmel_pioctrl->reg_base = devm_platform_ioremap_resource(pdev, 0);
>  	if (IS_ERR(atmel_pioctrl->reg_base))
> -- 
> 2.7.4
>