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

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Date:   Thu, 1 Jun 2023 20:41:40 -0400
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     andy.shevchenko@...il.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

On Fri, 2 Jun 2023 00:30:14 +0300
andy.shevchenko@...il.com wrote:

> 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.

Hi,
done.

> > +		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.

Changed return type to u8.

 
> > +{
> > +	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;

Done.


> > +	ret = device_property_read_u32_array(dev, "nxp,modem-control-line-ports",
> > +					     mctrl_port, count);
> > +	if (ret)
> > +		return mctrl_mask;
> 
> 		return 0;

Done.


> 	mctrl_mask = 0;

Done.

 
> > +	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(...);

I used negative to save on indentation, but it also fits by converting it to positive, so done.

 
> > +	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;

Done.

I will send a V7 soon with your Reviewed-by tag.

Thank you,
Hugo.

 
> >  	int i, ret;
> >  	struct sc16is7xx_port *s;
> 
> -- 
> With Best Regards,
> Andy Shevchenko