linux-kernel - Re: [PATCH v6 5/9] serial: sc16is7xx: fix regression with GPIO configuration

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Date:   Fri, 2 Jun 2023 00:30:14 +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>,
        stable@...r.kernel.org
Subject: Re: [PATCH v6 5/9] serial: sc16is7xx: fix regression with GPIO
 configuration

Thu, Jun 01, 2023 at 04:18:40PM -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.
> 
> Allow to specify GPIO or modem control line function in the device
> tree, and for each of the ports (A or B).
> 
> Do so by using the new device-tree property named
> "modem-control-line-ports" (property added in separate patch).
> 
> When registering GPIO chip controller, mask-out GPIO pins declared as
> modem control lines according to this new "modem-control-line-ports"
> 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

Almost good, a few remarks and if addressed as suggested,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

Thank you!

...

> +	if (!s->gpio_valid_mask)

I would use == 0, but it's up to you. Both will work equally.

> +		return 0;

...

> +static int sc16is7xx_setup_mctrl_ports(struct device *dev)

Not sure why int if you always return an unsigned value.
Otherwise return an error code when it's no defined mask
and check it in the caller.

> +{
> +	struct sc16is7xx_port *s = dev_get_drvdata(dev);
> +	int i;
> +	int ret;
> +	int count;
> +	u32 mctrl_port[2];
> +	u8 mctrl_mask = 0;

I would return 0 directly in the first two cases and split an assignment closer
to the first user.

> +	count = device_property_count_u32(dev, "nxp,modem-control-line-ports");
> +	if (count < 0 || count > ARRAY_SIZE(mctrl_port))
> +		return mctrl_mask;

		return 0;

> +	ret = device_property_read_u32_array(dev, "nxp,modem-control-line-ports",
> +					     mctrl_port, count);
> +	if (ret)
> +		return mctrl_mask;

		return 0;


	mctrl_mask = 0;

> +	for (i = 0; i < count; i++) {
> +		/* Use GPIO lines as modem control lines */
> +		if (mctrl_port[i] == 0)
> +			mctrl_mask |= SC16IS7XX_IOCONTROL_MODEM_A_BIT;
> +		else if (mctrl_port[i] == 1)
> +			mctrl_mask |= SC16IS7XX_IOCONTROL_MODEM_B_BIT;
> +	}

> +	if (!mctrl_mask)
> +		return mctrl_mask;

Maybe positive one?

	if (mctrl_mask)
		regmap_update_bits(...);

> +	regmap_update_bits(s->regmap,
> +			   SC16IS7XX_IOCONTROL_REG << SC16IS7XX_REG_SHIFT,
> +			   SC16IS7XX_IOCONTROL_MODEM_A_BIT |
> +			   SC16IS7XX_IOCONTROL_MODEM_B_BIT, mctrl_mask);
> +
> +	return mctrl_mask;
> +}

...

>  	unsigned long freq = 0, *pfreq = dev_get_platdata(dev);
>  	unsigned int val;
> +	u8 mctrl_mask = 0;

This assignment is redundant, so you simply can define it

>  	u32 uartclk = 0;

	u8 mctrl_mask;

>  	int i, ret;
>  	struct sc16is7xx_port *s;

-- 
With Best Regards,
Andy Shevchenko