linux-kernel - Re: [PATCH v3 08/11] serial: sc16is7xx: fix regression with GPIO configuration

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Date:   Thu, 25 May 2023 14:19:52 +0300
From:   andy.shevchenko@...il.com
To:     Hugo Villeneuve <hugo@...ovil.com>
Cc:     gregkh@...uxfoundation.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        jirislaby@...nel.org, jringle@...dpoint.com,
        tomasz.mon@...lingroup.com, l.perczak@...lintechnologies.com,
        linux-serial@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: Re: [PATCH v3 08/11] serial: sc16is7xx: fix regression with GPIO
 configuration

Thu, May 25, 2023 at 12:03:22AM -0400, Hugo Villeneuve kirjoitti:
> From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> 
> Commit 679875d1d880 ("sc16is7xx: Separate GPIOs from modem control lines")
> and commit 21144bab4f11 ("sc16is7xx: Handle modem status lines")
> changed the function of the GPIOs pins to act as modem control
> lines without any possibility of selecting GPIO function.
> 
> As a consequence, applications that depends on GPIO lines configured
> by default as GPIO pins no longer work as expected.
> 
> Also, the change to select modem control lines function was done only
> for channel A of dual UART variants (752/762). This was not documented
> in the log message.

> This new patch allows to specify GPIO or modem control line function
> in the device tree, and for each of the ports (A or B).

Imperative mood as stated in documentation, please.
Like "Allow to specify...".

> This is done by using the new device-tree property named
> "modem-control-line-ports" (property added in separate patch).
> 
> We also now reduce the number of exported GPIOs according to the
> modem-status-line-port DT property.
> 
> Boards that need to have GPIOS configured as modem control lines
> should add that property to their device tree. Here is a list of
> boards using the sc16is7xx driver in their device tree and that may
> need to be modified:
>     arm64/boot/dts/freescale/fsl-ls1012a-frdm.dts
>     mips/boot/dts/ingenic/cu1830-neo.dts
>     mips/boot/dts/ingenic/cu1000-neo.dts

...

> +#ifdef CONFIG_GPIOLIB

I'm wondering if we can avoid adding new ifdefferies...

> +	s->gpio_configured = devtype->nr_gpio;

The name of the variable is a bit vague WRT its content.
Shouldn't be as simple as the rvalue, i.e. s->nr_gpio?

> +#endif /* CONFIG_GPIOLIB */

...

> +		of_property_for_each_u32(dev->of_node, "nxp,modem-control-line-ports",
> +					 prop, p, u)

The driver so far is agnostic to property provider. Please keep it that way,
i.e. no of_ APIs.

> +			if (u < devtype->nr_uart) {

Hmm... What other can it be?

> +				/* Use GPIO lines as modem control lines */
> +				if (u == 0)
> +					val |= SC16IS7XX_IOCONTROL_MODEM_A_BIT;
> +				else if (u == 1)
> +					val |= SC16IS7XX_IOCONTROL_MODEM_B_BIT;
> +
> +#ifdef CONFIG_GPIOLIB
> +				if (s->gpio_configured >=
> +				    SC16IS7XX_GPIOS_PER_BANK)

On one line it will be better to read. Esp. taking into account the above remark.

> +					s->gpio_configured -=
> +						SC16IS7XX_GPIOS_PER_BANK;

Ditto.

> +#endif /* CONFIG_GPIOLIB */
> +			}

-- 
With Best Regards,
Andy Shevchenko