Date: Tue, 15 Apr 2014 12:30:27 -0700
From: David Cohen <david.a.cohen@linux.intel.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: wim@iguana.be, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
        x86@kernel.org, linux-kernel@vger.kernel.org,
        linux-watchdog@vger.kernel.org, gnomes@lxorguk.ukuu.org.uk
Subject: Re: [PATCH v3 2/2] x86: intel-mid: add watchdog platform code for
 Merrifield
Message-ID: <20140415193026.GI5986@psi-dev26.jf.intel.com>
References: <1397249407-5417-1-git-send-email-david.a.cohen@linux.intel.com>
 <1397587272-31152-1-git-send-email-david.a.cohen@linux.intel.com>
 <1397587272-31152-3-git-send-email-david.a.cohen@linux.intel.com>
 <20140415190902.GB7940@roeck-us.net>
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On Tue, Apr 15, 2014 at 12:09:02PM -0700, Guenter Roeck wrote:
> On Tue, Apr 15, 2014 at 11:41:12AM -0700, David Cohen wrote:
> > This patch adds platform code for Intel Merrifield.
> > Since the watchdog is not part of SFI table, we have no other option but
> > to manually register watchdog's platform device (argh!).
> > 
> argh ... does this really belong into the commit log ?

Yes. It means: "this developer was forced to do this ugly thing due to
fw-related sloppiness".

> 
> > Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
> > ---
> >  arch/x86/platform/intel-mid/device_libs/Makefile   |  1 +
> >  .../platform/intel-mid/device_libs/platform_wdt.c  | 63 ++++++++++++++++++++++
> >  2 files changed, 64 insertions(+)
> >  create mode 100644 arch/x86/platform/intel-mid/device_libs/platform_wdt.c
> > 
> > diff --git a/arch/x86/platform/intel-mid/device_libs/Makefile b/arch/x86/platform/intel-mid/device_libs/Makefile
> > index 097e7a7940d8..af9307f2cc28 100644
> > --- a/arch/x86/platform/intel-mid/device_libs/Makefile
> > +++ b/arch/x86/platform/intel-mid/device_libs/Makefile
> > @@ -20,3 +20,4 @@ obj-$(subst m,y,$(CONFIG_DRM_MEDFIELD)) += platform_tc35876x.o
> >  obj-$(subst m,y,$(CONFIG_SERIAL_MRST_MAX3110)) += platform_max3111.o
> >  # MISC Devices
> >  obj-$(subst m,y,$(CONFIG_KEYBOARD_GPIO)) += platform_gpio_keys.o
> > +obj-$(subst m,y,$(CONFIG_INTEL_MID_WATCHDOG)) += platform_wdt.o
> > diff --git a/arch/x86/platform/intel-mid/device_libs/platform_wdt.c b/arch/x86/platform/intel-mid/device_libs/platform_wdt.c
> > new file mode 100644
> > index 000000000000..653242110d57
> > --- /dev/null
> > +++ b/arch/x86/platform/intel-mid/device_libs/platform_wdt.c
> > @@ -0,0 +1,63 @@
> > +/*
> > + * platform_wdt.c: Watchdog platform library file
> > + *
> > + * (C) Copyright 2014 Intel Corporation
> > + * Author: David Cohen <david.a.cohen@linux.intel.com>
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; version 2
> > + * of the License.
> > + */
> > +
> > +#include <linux/init.h>
> > +#include <linux/intel-mid_wdt.h>
> 
> 	/platform_data/...

Ack

> 
> > +#include <linux/interrupt.h>
> > +#include <linux/platform_device.h>
> > +#include <asm/intel-mid.h>
> > +
> > +#define TANGIER_EXT_TIMER0_MSI 15
> > +
> > +static struct platform_device wdt_dev = {
> > +	.name = "intel_mid_wdt",
> > +	.id = -1,
> > +};
> > +
> > +static int tangier_probe(void)
> > +{
> > +	int ioapic;
> > +	struct io_apic_irq_attr irq_attr;
> > +
> 				= { };
> would ensure that there are no un-initialized variables
> if the structure definition ever changes.
> 
> Or just pre-initialize the entire structure as much as possible.

The first suggestion seems better.

> 
> > +	ioapic = mp_find_ioapic(TANGIER_EXT_TIMER0_MSI);
> > +	if (ioapic >= 0) {
> > +		irq_attr.ioapic = ioapic;
> > +		irq_attr.ioapic_pin = TANGIER_EXT_TIMER0_MSI;
> > +		irq_attr.trigger = 1;
> > +		irq_attr.polarity = 0; /* Active high */
> > +		io_apic_set_pci_routing(NULL, TANGIER_EXT_TIMER0_MSI,
> > +					&irq_attr);
> 
> No need for an error check ? I understand no one else does,
> but why does the function return an error if no one cares about it ?

That's an interesting question. But whatever is the answer, I believe
checking the error makes more sense. I'll change it.

> 
> > +	} else {
> > +		pr_warn("intel_mid_wdt: can not find interrupt %d in ioapic\n",
> > +			TANGIER_EXT_TIMER0_MSI);
> 
> As mentioned earlier, I think it would pake sense to pass
> struct platform_device * as argument and use dev_warn.
> 
> It would also enable you to use the irq passed from the parameter
> instead of checking for the hard-coded define.

Ack.

> 
> > +		return -EINVAL;
> 
> Why not return the error returned by mp_find_ioapic() ?

My intention was to ensure in this scenario we got the wrong IRQ. But it
perhaps makes more sense to keep the original error.

Thanks again for the review.

Br, David

> 
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static struct intel_mid_wdt_pdata tangier_pdata = {
> > +	.irq = TANGIER_EXT_TIMER0_MSI,
> > +	.probe = tangier_probe,
> > +};
> > +
> > +static int __init register_mid_wdt(void)
> > +{
> > +	if (intel_mid_identify_cpu() == INTEL_MID_CPU_CHIP_TANGIER) {
> > +		wdt_dev.dev.platform_data = &tangier_pdata;
> > +		return platform_device_register(&wdt_dev);
> > +	}
> > +
> > +	return -ENODEV;
> > +}
> > +
> > +rootfs_initcall(register_mid_wdt);
> > -- 
> > 1.9.1
> > 
> > --
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