linux-kernel - Re: [RFC 2/2] drivers: dma-mapping: parse per device reserved mem at probe time

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Date:   Mon, 27 Nov 2017 17:04:11 +0800
From:   Peng Fan <van.freenix@...il.com>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Peng Fan <peng.fan@....com>, hch@....de, robin.murphy@....com,
        gregkh@...uxfoundation.org, robh+dt@...nel.org,
        frowand.list@...il.com, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [RFC 2/2] drivers: dma-mapping: parse per device reserved mem at
 probe time

Hi Marek,

On Mon, Nov 27, 2017 at 09:44:20AM +0100, Marek Szyprowski wrote:
>Hi Peng,
>
>On 2017-11-27 09:37, Peng Fan wrote:
>> Hi Marek,
>> 
>> On Mon, Nov 27, 2017 at 09:31:00AM +0100, Marek Szyprowski wrote:
>> > Hi
>> > 
>> > On 2017-11-26 14:13, Peng Fan wrote:
>> > > Invoke of_reserved_mem_device_init at dma_configure, then
>> > > there is no need to call of_reserved_mem_device_init in device
>> > > specific probe function.
>> > > 
>> > > Signed-off-by: Peng Fan <peng.fan@....com>
>> > This has been already tried long time ago, without success:
>> > http://patches.linaro.org/patch/33558/
>> Thanks for the info. I should first search mail list before
>> sending out patches.
>
>It doesn't mean that I'm against such idea. I just pointed that I've
>already tried. That time, however there was no dma_configure() function
>yet, which seems to be better place for of_rmem_device_init().
>
>I would however always call of_dma_configure(), even when reserved mem
>node is there. IIRC on ARM64 that function configures dma_ops, without
>which no dma is possible at all.

So, you prefer this?
	if (dma_dev->of_node) {
+		of_reserved_mem_device_init(dev);
		ret = of_dma_configure(dev, dma_dev->of_node);

However in of_reserved_mem_device, there is also an call to
of_dma_configure.

"
	/* ensure that dma_ops is set for virtual devices
	 * using reserved memory
	 */
	 ret = of_dma_configure(dev, np);
"

If always call of_dma_configure, of_dma_configure maybe called twice.

I just checked more. of_reserved_mem_device_init only handle the first
memory-region. To nodes which have multiple memory-region, seems 2nd and etc
could not be handled, such as drivers/media/platform/s5p-mfc/s5p_mfc.c.

Thanks,
Peng.

>
>> 
>> Thanks,
>> Peng.
>> 
>> > > ---
>> > >    drivers/base/dma-mapping.c | 6 +++++-
>> > >    1 file changed, 5 insertions(+), 1 deletion(-)
>> > > 
>> > > diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
>> > > index e584eddef0a7..55dca06a7b55 100644
>> > > --- a/drivers/base/dma-mapping.c
>> > > +++ b/drivers/base/dma-mapping.c
>> > > @@ -12,6 +12,7 @@
>> > >    #include <linux/export.h>
>> > >    #include <linux/gfp.h>
>> > >    #include <linux/of_device.h>
>> > > +#include <linux/of_reserved_mem.h>
>> > >    #include <linux/slab.h>
>> > >    #include <linux/vmalloc.h>
>> > > @@ -351,7 +352,9 @@ int dma_configure(struct device *dev)
>> > >    	}
>> > >    	if (dma_dev->of_node) {
>> > > -		ret = of_dma_configure(dev, dma_dev->of_node);
>> > > +		ret = of_reserved_mem_device_init(dev);
>> > > +		if (ret)
>> > > +			ret = of_dma_configure(dev, dma_dev->of_node);
>> > >    	} else if (has_acpi_companion(dma_dev)) {
>> > >    		attr = acpi_get_dma_attr(to_acpi_device_node(dma_dev->fwnode));
>> > >    		if (attr != DEV_DMA_NOT_SUPPORTED)
>> > > @@ -367,5 +370,6 @@ int dma_configure(struct device *dev)
>> > >    void dma_deconfigure(struct device *dev)
>> > >    {
>> > >    	of_dma_deconfigure(dev);
>> > > +	of_reserved_mem_device_release(dev);
>> > >    	acpi_dma_deconfigure(dev);
>> > >    }
>
>Best regards
>-- 
>Marek Szyprowski, PhD
>Samsung R&D Institute Poland
>

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