linux-kernel - Re: [PATCH-v8] serial: 8250_dw: Add support for big-endian MMIO accesses

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Message-ID: <20151210103338.GE4884@kuha.fi.intel.com>
Date:	Thu, 10 Dec 2015 12:33:38 +0200
From:	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:	Noam Camus <noamc@...hip.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"jslaby@...e.com" <jslaby@...e.com>,
	"peter@...leysoftware.com" <peter@...leysoftware.com>,
	"fransklaver@...il.com" <fransklaver@...il.com>,
	"Alexey.Brodkin@...opsys.com" <Alexey.Brodkin@...opsys.com>,
	"vgupta@...opsys.com" <vgupta@...opsys.com>
Subject: Re: [PATCH-v8] serial: 8250_dw: Add support for big-endian MMIO
 accesses

On Thu, Dec 10, 2015 at 11:31:04AM +0200, Heikki Krogerus wrote:
> Hi Noam,
> 
> On Thu, Dec 10, 2015 at 07:26:42AM +0000, Noam Camus wrote:
> > >From: Heikki Krogerus [mailto:heikki.krogerus@...ux.intel.com] 
> > >Sent: Wednesday, December 09, 2015 3:20 PM
> > 
> > 
> > >> @@ -171,7 +174,8 @@ static void dw8250_serial_out32(struct uart_port *p, int offset, int value)
> > >>  			if ((value & ~UART_LCR_SPAR) == (lcr & ~UART_LCR_SPAR))
> > >>  				return;
> > >>  			dw8250_force_idle(p);
> > >> -			writel(value, p->membase + (UART_LCR << p->regshift));
> > >> +			d->serial_out(value,
> > >> +				      p->membase + (UART_LCR << p->regshift));
> > >>  		}
> > 
> > >.. The way I see it, this is the only place where you would really need the
> > >new private serial_in/out hooks, so why not just check the >iotype here and
> > >based on that use writeb/writel/iowrite32be or what ever ..
> > 
> > In previous versions (V2) Greg dis-liked using iotype here this is why I added
> > the private serial_in/serial_out
> 
> I couldn't find that comment in the thread? All he said in his
> comment for this was that you should use real if condition instead of
> the ternary operator you had there (condition ? true : false).
> 
> Why would it not be acceptable? If it would really not be acceptable
> (which I don't believe) then you should simply duplicate the lcr
> checking to dw8250_seria_out32be like it is done now in
> dw8250_serial_out and dw8250_serial_out32, but there still is no need
> for the private serial_in/out hooks.
> 
> I'm attaching a diff that I think would work as a good starting point
> for you.

Now actually attaching the diff :).

-- 
heikki

View attachment "dw8250_check_lcr.diff" of type "text/plain" (2913 bytes)