Received-SPF: pass (google.com: domain of linux-wireless+bounces-2940-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45d1:ec00::1 as permitted sender) client-ip=2604:1380:45d1:ec00::1;
Date: Thu, 1 Feb 2024 13:40:07 +0200
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@toke.dk>,
	Kalle Valo <kvalo@kernel.org>, Arend van Spriel <aspriel@gmail.com>,
	Franky Lin <franky.lin@broadcom.com>,
	Hante Meuleman <hante.meuleman@broadcom.com>,
	Arnd Bergmann <arnd@arndb.de>, Lee Jones <lee@kernel.org>,
	Brian Norris <briannorris@chromium.org>,
	Srinivasan Raju <srini.raju@purelifi.com>,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
	brcm80211-dev-list.pdl@broadcom.com
Subject: Re: [PATCH 1/6] wifi: ath9k: Obtain system GPIOS from descriptors
Message-ID: <ZbuDF2-m8oJofpyl@smile.fi.intel.com>
References: <20240131-descriptors-wireless-v1-0-e1c7c5d68746@linaro.org>
 <20240131-descriptors-wireless-v1-1-e1c7c5d68746@linaro.org>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20240131-descriptors-wireless-v1-1-e1c7c5d68746@linaro.org>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo

On Wed, Jan 31, 2024 at 11:37:20PM +0100, Linus Walleij wrote:
> The ath9k has an odd use of system-wide GPIOs: if the chip
> does not have internal GPIO capability, it will try to obtain a
> GPIO line from the system GPIO controller:
> 
>   if (BIT(gpio) & ah->caps.gpio_mask)
>         ath9k_hw_gpio_cfg_wmac(...);
>   else if (AR_SREV_SOC(ah))
>         ath9k_hw_gpio_cfg_soc(ah, gpio, out, label);
> 
> Where ath9k_hw_gpio_cfg_soc() will attempt to issue
> gpio_request_one() passing the local GPIO number of the controller
> (0..31) to gpio_request_one().
> 
> This is somewhat peculiar and possibly even dangerous: there is
> nowadays no guarantee of the numbering of these system-wide
> GPIOs, and assuming that GPIO 0..31 as used by ath9k would
> correspond to GPIOs 0..31 on the system as a whole seems a bit
> wild.
> 
> My best guess is that everyone actually using this driver has
> support for the local (custom) GPIO API and the bit in
> h->caps.gpio_mask is always set for any GPIO the driver may
> try to obtain, so this facility to use system-wide GPIOs is
> actually unused and could be deleted.
> 
> Anyway: I cannot know if this is really the case, so implement
> a fallback handling using GPIO descriptors obtained from the
> ah->dev device indexed 0..31. These can for example be passed
> in the device tree, ACPI or through board files. I doubt that
> anyone will use them, but this makes it possible to obtain a
> system-wide GPIO for any of the 0..31 GPIOs potentially
> requested by the driver.

...

> +	/* Obtains a system specific GPIO descriptor from another GPIO controller */
> +	gpiod = devm_gpiod_get_index(ah->dev, NULL, gpio, flags);

> +

Unnecessary blank line, please don't add it.

> +	if (IS_ERR(gpiod)) {
> +		err = PTR_ERR(gpiod);
>  		ath_err(ath9k_hw_common(ah), "request GPIO%d failed:%d\n",
>  			gpio, err);
>  		return;
>  	}

-- 
With Best Regards,
Andy Shevchenko