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

[Marek Szyprowski]

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@xxxxxxx>
> > 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.

> 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