Re: [PATCH 4/6] MIPS: SGI-IP27: fix readb/writeb addressing

From: Thomas Bogendoerfer <tbogendoerfer@suse.de>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
	Paul Burton <paul.burton@mips.com>,
	James Hogan <jhogan@kernel.org>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	Lee Jones <lee.jones@linaro.org>,
	"David S. Miller" <davem@davemloft.net>,
	Alessandro Zummo <a.zummo@towertech.it>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jslaby@suse.com>,
	linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-input@vger.kernel.org, netdev@vger.kernel.org,
	linux-rtc@vger.kernel.org, linux-serial@vger.kernel.org
Subject: Re: [PATCH 4/6] MIPS: SGI-IP27: fix readb/writeb addressing
Date: Mon, 8 Apr 2019 20:53:28 +0200	[thread overview]
Message-ID: <20190408205328.062042a4f6e12f750bd4c05e@suse.de> (raw)
In-Reply-To: <20190408145834.GO7480@piout.net>

On Mon, 8 Apr 2019 16:58:34 +0200
Alexandre Belloni <alexandre.belloni@bootlin.com> wrote:

> On 08/04/2019 16:20:56+0200, Thomas Bogendoerfer wrote:
> > diff --git a/drivers/rtc/rtc-m48t35.c b/drivers/rtc/rtc-m48t35.c
> > index 0cf6507de3c7..05f0d91366af 100644
> > --- a/drivers/rtc/rtc-m48t35.c
> > +++ b/drivers/rtc/rtc-m48t35.c
> > @@ -24,6 +24,16 @@
> >  
> >  struct m48t35_rtc {
> >  	u8	pad[0x7ff8];    /* starts at 0x7ff8 */
> > +#ifdef CONFIG_SGI_IP27
> > +	u8	hour;
> > +	u8	min;
> > +	u8	sec;
> > +	u8	control;
> > +	u8	year;
> > +	u8	month;
> > +	u8	date;
> > +	u8	day;
> > +#else
> 
> I'm not sure why the RTC driver has to know about that. Shouldn't your
> accessors be fixing that?

no, because the hardware is weird. RTC is connected to IOC3 byte bus and IOC3 is
connected to PCI. With a correct readb for PCI bus access to RTC behind IOC3 is byte
swapped.

Thomas.

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