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

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Date:   Thu, 1 Jun 2023 21:25:14 -0400
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Hugo Villeneuve <hugo@...ovil.com>
Cc:     andy.shevchenko@...il.com, 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 Thu, 1 Jun 2023 20:41:40 -0400
Hugo Villeneuve <hugo@...ovil.com> wrote:

> 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.

Hi Andy,
Greg did not yet respond to my email about the proposed tags, but if the new order of the patches and the stable tags I added seems ok to you, I will resend V7. It will then probably easier for Greg to comment directly on V7 for the stable tags (Cc:).

Hugo.