linux-kernel - Re: [PATCH v3 5/7] mfd: ioc3: Add driver for SGI IOC3 chip

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Message-ID: <20190809122254.GN3600@piout.net>
Date:   Fri, 9 Aug 2019 14:22:54 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Thomas Bogendoerfer <tbogendoerfer@...e.de>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-mips@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        netdev@...r.kernel.org, linux-rtc@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v3 5/7] mfd: ioc3: Add driver for SGI IOC3 chip

On 29/07/2019 20:45:57+0200, Thomas Bogendoerfer wrote:
> On Thu, 25 Jul 2019 12:47:16 +0100
> Lee Jones <lee.jones@...aro.org> wrote:
> 
> > On Thu, 13 Jun 2019, Thomas Bogendoerfer wrote:
> > > +/*
> > > + * On IP30 the RTC (a DS1687) is behind the IOC3 on the generic
> > > + * ByteBus regions. We have to write the RTC address of interest to
> > > + * IOC3_BYTEBUS_DEV1, then read the data from IOC3_BYTEBUS_DEV2.
> > > + * rtc->regs already points to IOC3_BYTEBUS_DEV1.
> > > + */
> > > +#define IP30_RTC_ADDR(rtc) (rtc->regs)
> > > +#define IP30_RTC_DATA(rtc) ((rtc->regs) + IOC3_BYTEBUS_DEV2 - IOC3_BYTEBUS_DEV1)
> > > +
> > > +static u8 ip30_rtc_read(struct ds1685_priv *rtc, int reg)
> > > +{
> > > +	writeb((reg & 0x7f), IP30_RTC_ADDR(rtc));
> > > +	return readb(IP30_RTC_DATA(rtc));
> > > +}
> > > +
> > > +static void ip30_rtc_write(struct ds1685_priv *rtc, int reg, u8 value)
> > > +{
> > > +	writeb((reg & 0x7f), IP30_RTC_ADDR(rtc));
> > > +	writeb(value, IP30_RTC_DATA(rtc));
> > > +}
> > 
> > Why is this not in the RTC driver?
> 
> because rtc1685 is used in different systems and accessing the chip
> differs between those systems. 
> 
> > > +static struct ds1685_rtc_platform_data ip30_rtc_platform_data = {
> > > +	.bcd_mode = false,
> > > +	.no_irq = false,
> > > +	.uie_unsupported = true,
> > > +	.alloc_io_resources = true,
> > 
> > > +	.plat_read = ip30_rtc_read,
> > > +	.plat_write = ip30_rtc_write,
> > 
> > Call-backs in a non-subsystem API is pretty ugly IMHO.
> 
> I agree
> 
> > Where are these called from?
> 
> drivers/rtc/rtc-ds1685.c
> 
> I could do the same as done for serial8250 and add an additional .c file
> in  drivers/rtc which handles this for SGI-IP30. Alexandre would this work
> for you as well ?
> 

As it is not particularly big, you could put that directly in
rtc-ds1685.c.


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com