linux-kernel - Re: [RFC/PATCH 6/9] drivers: platform: Configure dma operations at probe time

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Message-ID: <6368894.049YN38x4u@avalon>
Date:	Mon, 25 May 2015 01:41:42 +0300
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Robin Murphy <robin.murphy@....com>
Cc:	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Arnd Bergmann <arnd@...db.de>,
	Mitchel Humpherys <mitchelh@...eaurora.org>,
	Joreg Roedel <joro@...tes.org>,
	Will Deacon <Will.Deacon@....com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC/PATCH 6/9] drivers: platform: Configure dma operations at probe time

Hi Robin,

On Tuesday 19 May 2015 11:39:17 Robin Murphy wrote:
> On 15/05/15 00:00, Laurent Pinchart wrote:
> > Configuring DMA ops at probe time will allow deferring device probe when
> > the IOMMU isn't available yet.
> 
> This is great, as I think it also subtly solves the ordering problem the
> current domain allocation has with platform devices. WRT to your comment
> on the other thread, this actually makes things slightly saner for IOMMU
> groups - the group assignment has to happen after device creation or
> else some sysfs stuff blows up, so of_xlate is far too early and the
> add_device callback is a reasonable place for it to be (until we can
> move it out of every driver and into bus code). However, we're currently
> attaching the device to the automatic domain long before that, so things
> happen logically backwards and drivers like the ARM SMMU which actually
> use the group to store relevant data get all confused.
> 
> With this change, the existing attach_device call in arch_setup_dma_ops
> will actually work far more reliably, and I might be able to revive my
> attempt to port the ARM SMMU driver over to of_xlate :D

Please do :-) I second IOMMU driver using the of_xlate + probe deferral 
mechanism would help validate this patch series.

> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@...asonboard.com>
> > ---
> > 
> >   drivers/base/platform.c | 9 +++++++++
> >   drivers/of/platform.c   | 7 +++----
> >   2 files changed, 12 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > index ebf034b97278..508a866859dc 100644
> > --- a/drivers/base/platform.c
> > +++ b/drivers/base/platform.c
> > @@ -516,6 +516,10 @@ static int platform_drv_probe(struct device *_dev)
> >   	if (ret < 0)
> >   		return ret;
> > 
> > +	ret = of_dma_configure_ops(_dev, _dev->of_node);
> > +	if (ret < 0)
> > +		goto done;
> > +
> >   	ret = dev_pm_domain_attach(_dev, true);
> >   	if (ret != -EPROBE_DEFER) {
> >   		ret = drv->probe(dev);
> > @@ -523,6 +527,10 @@ static int platform_drv_probe(struct device *_dev)
> >   			dev_pm_domain_detach(_dev, true);
> >   	}
> > 
> > +	if (ret)
> > +		of_dma_deconfigure(_dev);
> > +
> > 
> > +done:
> >   	if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
> >   		dev_warn(_dev, "probe deferral not supported\n");
> >   		ret = -ENXIO;
> > @@ -544,6 +552,7 @@ static int platform_drv_remove(struct device *_dev)
> > 
> >   	ret = drv->remove(dev);
> >   	dev_pm_domain_detach(_dev, true);
> > +	of_dma_deconfigure(_dev);
> >   	return ret;
> >   }
> > 
> > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > index 9a29f09b7723..fc939bec799e 100644
> > --- a/drivers/of/platform.c
> > +++ b/drivers/of/platform.c
> > @@ -178,10 +178,8 @@ static struct platform_device
> > *of_platform_device_create_pdata(
> >   	dev->dev.bus = &platform_bus_type;
> >   	dev->dev.platform_data = platform_data;
> >   	of_dma_configure_masks(&dev->dev, dev->dev.of_node);
> > -	of_dma_configure_ops(&dev->dev, dev->dev.of_node);
> > 
> >   	if (of_device_add(dev) != 0) {
> > -		of_dma_deconfigure(&dev->dev);
> >   		platform_device_put(dev);
> >   		goto err_clear_flag;
> >   	}
> > @@ -465,11 +463,12 @@ static int of_platform_device_destroy(struct device
> > *dev, void *data)
> >   	if (dev->bus == &platform_bus_type)
> >   		platform_device_unregister(to_platform_device(dev));
> >   
> >   #ifdef CONFIG_ARM_AMBA
> > -	else if (dev->bus == &amba_bustype)
> > +	else if (dev->bus == &amba_bustype) {
> >   		amba_device_unregister(to_amba_device(dev));
> > +		of_dma_deconfigure(dev);
> > +	}
> >   #endif
> > 
> > -	of_dma_deconfigure(dev);
> >   	of_node_clear_flag(dev->of_node, OF_POPULATED);
> >   	of_node_clear_flag(dev->of_node, OF_POPULATED_BUS);
> >   	return 0;

-- 
Regards,

Laurent Pinchart

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