Re: [PATCH v5 2/3] memory: omap-gpmc: add support for wait pin polarity

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 16/09/2022 14:07, B. Niedermayr wrote:
> From: Benedikt Niedermayr <benedikt.niedermayr@siemens.com>
> 
> The waitpin polarity can be configured via the WAITPIN<X>POLARITY bits
> in the GPMC_CONFIG register. This is currently not supported by the
> driver. This patch adds support for setting the required register bits
> with the "gpmc,wait-pin-polarity" dt-property.
> 
> Signed-off-by: Benedikt Niedermayr <benedikt.niedermayr@siemens.com>
> ---
>  drivers/memory/omap-gpmc.c              | 27 +++++++++++++++++++++++++
>  include/linux/platform_data/gpmc-omap.h |  6 ++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/drivers/memory/omap-gpmc.c b/drivers/memory/omap-gpmc.c
> index ea495e93766b..2853fc28bccc 100644
> --- a/drivers/memory/omap-gpmc.c
> +++ b/drivers/memory/omap-gpmc.c
> @@ -132,6 +132,7 @@
>  #define GPMC_CONFIG_DEV_SIZE	0x00000002
>  #define GPMC_CONFIG_DEV_TYPE	0x00000003
>  
> +#define GPMC_CONFIG_WAITPINPOLARITY(pin)	(BIT(pin) << 8)
>  #define GPMC_CONFIG1_WRAPBURST_SUPP     (1 << 31)
>  #define GPMC_CONFIG1_READMULTIPLE_SUPP  (1 << 30)
>  #define GPMC_CONFIG1_READTYPE_ASYNC     (0 << 29)
> @@ -1882,6 +1883,17 @@ int gpmc_cs_program_settings(int cs, struct gpmc_settings *p)
>  
>  	gpmc_cs_write_reg(cs, GPMC_CS_CONFIG1, config1);
>  
> +	if (p->wait_pin_polarity != WAITPINPOLARITY_DEFAULT) {
> +		config1 = gpmc_read_reg(GPMC_CONFIG);
> +
> +		if (p->wait_pin_polarity == WAITPINPOLARITY_ACTIVE_LOW)
> +			config1 &= ~GPMC_CONFIG_WAITPINPOLARITY(p->wait_pin);
> +		else if (p->wait_pin_polarity == WAITPINPOLARITY_ACTIVE_HIGH)
> +			config1 |= GPMC_CONFIG_WAITPINPOLARITY(p->wait_pin);
> +
> +		gpmc_write_reg(GPMC_CONFIG, config1);

What happens if wait pin is shared and you have different polarities in
both of devices?

> +	}
> +
>  	return 0;
>  }
>  
> @@ -1981,7 +1993,22 @@ void gpmc_read_settings_dt(struct device_node *np, struct gpmc_settings *p)
>  				__func__);
>  	}
>  
> +	p->wait_pin_polarity = WAITPINPOLARITY_DEFAULT;
> +
>  	if (!of_property_read_u32(np, "gpmc,wait-pin", &p->wait_pin)) {
> +		if (!of_property_read_u32(np, "gpmc,wait-pin-polarity",
> +					  &p->wait_pin_polarity)) {
> +			if (p->wait_pin_polarity != WAITPINPOLARITY_ACTIVE_HIGH &&
> +			    p->wait_pin_polarity != WAITPINPOLARITY_ACTIVE_LOW &&
> +			    p->wait_pin_polarity != WAITPINPOLARITY_DEFAULT) {

WAITPINPOLARITY_DEFAULT is not allowed in DT, so you can skip it.

> +				pr_err("%s: Invalid wait-pin-polarity (pin: %d, pol: %d)\n",

dev_err, not pr_err

> +				       __func__, p->wait_pin, p->wait_pin_polarity);

Skip __func__

> +				p->wait_pin_polarity = WAITPINPOLARITY_DEFAULT;
> +			}
> +		} else {
> +			pr_err("%s: Failed to read gpmc,wait-pin-polarity\n", __func__);

Ditto.

> +		}
> +
>  		p->wait_on_read = of_property_read_bool(np,
>  							"gpmc,wait-on-read");
>  		p->wait_on_write = of_property_read_bool(np,
> diff --git a/include/linux/platform_data/gpmc-omap.h b/include/linux/platform_data/gpmc-omap.h
> index c9cc4e32435d..c46c28069c31 100644
> --- a/include/linux/platform_data/gpmc-omap.h
> +++ b/include/linux/platform_data/gpmc-omap.h
> @@ -136,6 +136,11 @@ struct gpmc_device_timings {
>  #define GPMC_MUX_AAD			1	/* Addr-Addr-Data multiplex */
>  #define GPMC_MUX_AD			2	/* Addr-Data multiplex */
>  
> +/* Wait pin polarity values */
> +#define WAITPINPOLARITY_DEFAULT -1

Missing prefix. This is a global header.

> +#define WAITPINPOLARITY_ACTIVE_LOW 0
> +#define WAITPINPOLARITY_ACTIVE_HIGH 1
> +
>  struct gpmc_settings {
>  	bool burst_wrap;	/* enables wrap bursting */
>  	bool burst_read;	/* enables read page/burst mode */
> @@ -149,6 +154,7 @@ struct gpmc_settings {
>  	u32 device_width;	/* device bus width (8 or 16 bit) */
>  	u32 mux_add_data;	/* multiplex address & data */
>  	u32 wait_pin;		/* wait-pin to be used */
> +	u32 wait_pin_polarity;	/* wait-pin polarity */

Skip the comment. You just copied the name of variable. Such comments
are useless.

We do not have KPIs in kernel to achieve some comment-ratio...

Best regards,
Krzysztof