linux-kernel - Re: [PATCH 3/3] serial: amba-pl011: add ACPI support to AMBA probe

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Message-ID: <20151201122100.GB4036@xora-haswell.xora.org.uk>
Date:	Tue, 1 Dec 2015 12:21:00 +0000
From:	Graeme Gregory <gg@...mlogic.co.uk>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Graeme Gregory <graeme.gregory@...aro.org>,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org, shannon.zhao@...aro.org,
	Len Brown <lenb@...nel.org>,
	Russell King <linux@....linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 3/3] serial: amba-pl011: add ACPI support to AMBA probe

On Tue, Dec 01, 2015 at 03:21:47AM +0100, Rafael J. Wysocki wrote:
> On Wednesday, September 30, 2015 11:38:50 AM Graeme Gregory wrote:
> > In ACPI this device is only defined in SBSA mode so
> > if we are probing from ACPI use this mode.
> > 
> > Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> > Cc: Len Brown <lenb@...nel.org>
> > Cc: Russell King <linux@....linux.org.uk>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Signed-off-by: Graeme Gregory <graeme.gregory@...aro.org>
> > ---
> >  drivers/tty/serial/amba-pl011.c | 32 +++++++++++++++++++++-----------
> >  1 file changed, 21 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> > index fd27e98..55209aa 100644
> > --- a/drivers/tty/serial/amba-pl011.c
> > +++ b/drivers/tty/serial/amba-pl011.c
> > @@ -2368,18 +2368,28 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
> >  	if (!uap)
> >  		return -ENOMEM;
> >  
> > -	uap->clk = devm_clk_get(&dev->dev, NULL);
> > -	if (IS_ERR(uap->clk))
> > -		return PTR_ERR(uap->clk);
> > -
> > -	uap->vendor = vendor;
> > -	uap->lcrh_rx = vendor->lcrh_rx;
> > -	uap->lcrh_tx = vendor->lcrh_tx;
> > -	uap->fifosize = vendor->get_fifosize(dev);
> > +	/* ACPI only defines SBSA variant */
> > +	if (!ACPI_COMPANION(&dev->dev)) {
> 
> It would read more straightforward if you did
> 
> 	if (ACPI_COMPANION(&dev->dev)) {
> 		<handle the ACPI case>
> 	} else {
> 		<handle the non-ACPI case>
> 	}
> 

This was something I debated about whether to put the ACPI case or the
common case first. I can certainly reverse it.

> > +		uap->clk = devm_clk_get(&dev->dev, NULL);
> > +		if (IS_ERR(uap->clk))
> > +			return PTR_ERR(uap->clk);
> > +
> > +		uap->vendor = vendor;
> > +		uap->lcrh_rx = vendor->lcrh_rx;
> > +		uap->lcrh_tx = vendor->lcrh_tx;
> > +		uap->fifosize = vendor->get_fifosize(dev);
> > +		uap->port.ops = &amba_pl011_pops;
> > +		snprintf(uap->type, sizeof(uap->type), "PL011 rev%u",
> > +				amba_rev(dev));
> > +	 } else {
> > +		uap->vendor	= &vendor_sbsa;
> > +		uap->fifosize	= 32;
> > +		uap->port.ops	= &sbsa_uart_pops;
> > +		uap->fixed_baud = 115200;
> > +
> > +		snprintf(uap->type, sizeof(uap->type), "SBSA");
> 
> This looks sort of heavy-handed.
> 
> Is this the only possible configuration of the device in the ACPI case?
> 

As far as I can tell yes, but ARM haven't actually published a document
to state that as fact.

This does replace the platform_probe that Russel was unhappy about for
the ACPI case.

Graeme

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