Re: [PATCH 1/3] ARM: pmu: add OF probing support

[Grant Likely <grant.likely@secretlab.ca>]

On Wed, Jun 08, 2011 at 11:40:01AM -0500, Rob Herring wrote:
> Mark,
> 
> On 06/08/2011 10:54 AM, Mark Rutland wrote:
> >Hi,
> >
> >>  static int __devinit pmu_device_probe(struct platform_device *pdev)
> >>  {
> >>+	enum arm_pmu_type type = pdev->id;
> >>
> >>-	if (pdev->id<  0 || pdev->id>= ARM_NUM_PMU_DEVICES) {
> >>+	if (pdev->dev.of_node)
> >>+		type = ARM_PMU_DEVICE_CPU;
> >>+
> >>+	if (type<  0 || type>= ARM_NUM_PMU_DEVICES) {
> >>  		pr_warning("received registration request for unknown "
> >>  				"device %d\n", pdev->id);
> >>  		return -EINVAL;
> >>  	}
> >>
> >>-	if (pmu_devices[pdev->id])
> >>+	if (pmu_devices[type])
> >>  		pr_warning("registering new PMU device type %d overwrites "
> >>-				"previous registration!\n", pdev->id);
> >>+				"previous registration!\n", type);
> >>  	else
> >>  		pr_info("registered new PMU device of type %d\n",
> >>-				pdev->id);
> >>+				type);
> >>
> >>-	pmu_devices[pdev->id] = pdev;
> >>+	pmu_devices[type] = pdev;
> >>  	return 0;
> >>  }
> >
> >I don't think this is the best way to handle the type when we've got an FDT
> >description:
> >
> >* release_pmu hasn't been updated to match the type logic here, so it might do
> >   anything when handed a platform_device initialised by FDT code.
> >
> >* the warning message for an invalid registration still uses pdev->id rather
> >   than type. This can't currently be reached when the PMU was handed to us via
> >   FDT, but it may confuse refactoring later on.
> >
> >* If we want to add a new PMU type, we'll have to add more logic to
> >   pmu_device_probe. Given that work is going on to add support for system PMUs,
> >   this doesn't seem particularly brilliant.
> >
> >>+static struct of_device_id pmu_device_ids[] = {
> >>+	{ .compatible = "arm,cortex-a9-pmu" },
> >>+	{ .compatible = "arm,cortex-a8-pmu" },
> >>+	{ .compatible = "arm,arm1136-pmu" },
> >>+	{ .compatible = "arm,arm1176-pmu" },
> >>+	{},
> >>+};
> >>+
> >>  static struct platform_driver pmu_driver = {
> >>  	.driver		= {
> >>  		.name	= "arm-pmu",
> >>+		.of_match_table = pmu_device_ids,
> >>  	},
> >>  	.probe		= pmu_device_probe,
> >>  };
> >
> >This all seems fine for handling CPU PMUs.
> >
> >I think that a better strategy would be to separate the type logic from the
> >registration. I have a patch for this:
> >http://lists.infradead.org/pipermail/linux-arm-kernel/2011-June/052455.html
> >
> >With it, you won't need to change pmu_device_probe, and adding FDT support
> >should just be a matter of adding the of_match_table.
> >
> 
> Okay. I'll rebase mine on top of your changes.

The DT binding looks good to me though.

g.