linux-kernel - Re: [PATCH v3 03/11] serial: sc16is7xx: mark IOCONTROL register as volatile

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Date:   Thu, 25 May 2023 09:45:06 -0400
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, Jiri Slaby <jirislaby@...nel.org>,
        jringle@...dpoint.com, tomasz.mon@...lingroup.com,
        l.perczak@...lintechnologies.com,
        linux-serial <linux-serial@...r.kernel.org>,
        devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        linux-gpio@...r.kernel.org,
        Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: Re: [PATCH v3 03/11] serial: sc16is7xx: mark IOCONTROL register as
 volatile

On Thu, 25 May 2023 14:02:19 +0300 (EEST)
Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com> wrote:

> On Thu, 25 May 2023, Hugo Villeneuve wrote:
> 
> > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > 
> > Bit SRESET (3) is cleared when a reset operation is completed. Having
> > the IOCONTROL register as non-volatile will always read SRESET as 1.
> > Therefore mark IOCONTROL register as a volatile register.
> > 
> > Fixes: dfeae619d781 ("serial: sc16is7xx")
> > Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> 
> What is the impact of this problem? That is, what doesn't work? I only see 
> writes to SC16IS7XX_IOCONTROL_REG. If there are no concrete problems 
> fixed, don't put Fixes tag.

Hi,
there is a concrete problem when dumping the registers as the value read for bit SRESET is incorrect, but it doesn't impact running code.

I can remove the Fixes.

Hugo.


> > ---
> >  drivers/tty/serial/sc16is7xx.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> > index 00054bb49780..a7c4da3cfd2b 100644
> > --- a/drivers/tty/serial/sc16is7xx.c
> > +++ b/drivers/tty/serial/sc16is7xx.c
> > @@ -488,6 +488,7 @@ static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
> >  	case SC16IS7XX_TXLVL_REG:
> >  	case SC16IS7XX_RXLVL_REG:
> >  	case SC16IS7XX_IOSTATE_REG:
> > +	case SC16IS7XX_IOCONTROL_REG:
> >  		return true;
> >  	default:
> >  		break;
> > 
>