Re: [PATCH v6 3/7] of: fix size when dma-range is not used

[Murali Karicheri]

On 02/06/2015 10:12 AM, Catalin Marinas wrote:
> On Fri, Feb 06, 2015 at 02:54:23PM +0000, Murali Karicheri wrote:
> > On 02/06/2015 09:38 AM, Catalin Marinas wrote:
> > > On Thu, Feb 05, 2015 at 09:52:55PM +0000, Murali Karicheri wrote:
> > > > Fix the dma-range size when the DT attribute is missing. i.e  set size to
> > > > dev->coherent_dma_mask + 1 instead of dev->coherent_dma_mask. Also add
> > > > code to check invalid values of size configured in DT and log error.
> > > >
> > > > Cc: Joerg Roedel<joro@xxxxxxxxxx>
> > > > Cc: Grant Likely<grant.likely@xxxxxxxxxx>
> > > > Cc: Rob Herring<robh+dt@xxxxxxxxxx>
> > > > Cc: Bjorn Helgaas<bhelgaas@xxxxxxxxxx>
> > > > Cc: Will Deacon<will.deacon@xxxxxxx>
> > > > Cc: Russell King<linux@xxxxxxxxxxxxxxxx>
> > > > Cc: Arnd Bergmann<arnd@xxxxxxxx>
> > > > Cc: Suravee Suthikulpanit<Suravee.Suthikulpanit@xxxxxxx>
> > > >
> > > > Signed-off-by: Murali Karicheri<m-karicheri2@xxxxxx>
> > > > ---
> > > >    drivers/of/device.c |   17 ++++++++++++++++-
> > > >    1 file changed, 16 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/of/device.c b/drivers/of/device.c
> > > > index 2de320d..314c8a9 100644
> > > > --- a/drivers/of/device.c
> > > > +++ b/drivers/of/device.c
> > > > @@ -105,9 +105,24 @@ void of_dma_configure(struct device *dev, struct device_node *np)
> > > >    	ret = of_dma_get_range(np,&dma_addr,&paddr,&size);
> > > >    	if (ret<   0) {
> > > >    		dma_addr = offset = 0;
> > > > -		size = dev->coherent_dma_mask;
> > > > +		size = dev->coherent_dma_mask + 1;
> > > >    	} else {
> > > >    		offset = PFN_DOWN(paddr - dma_addr);
> > > > +
> > > > +		/*
> > > > +		 * Add a work around to treat the size as mask + 1 in case
> > > > +		 * it is defined in DT as a mask.
> > > > +		 */
> > > > +		if (size&   1) {
> > > > +			dev_warn(dev, "Invalid size 0x%llx for dma-range\n",
> > > > +				 size);
> > > > +			size = size + 1;
> > > > +		}
> > > > +
> > > > +		if (!size) {
> > > > +			dev_err(dev, "Adjusted size 0x%llx invalid\n", size);
> > > > +			return;
> > > > +		}
> > >
> > > Would it make sense to set coherent_dma_mask to 0 here to make this more
> > > noticeable? It can be done together with the mask calculation from size.
> >
> > I guess you are the following in the code.
> >
> > if (!size) {
> > 		dev->coherent_dma_mask = 0;
> > 		dev_err(dev, "Adjusted size 0x%llx invalid\n", size);
> > 		return;
> > }
> >
> > Not sure how this is going to help and how this get handled by the
> > caller and subsequent logic. Probably it will cause probe to fail, with
> > some helpful error code.
>
> Not sure how it will fail, maybe the driver figures out that DMA isn't
> available and say something or switch to PIO. I guess you can leave it
> as 32-bit mask by default for now even in case of size == 0.
>
> BTW, since pci_device_add() already sets coherent_dma_mask, you could
> add another check at the beginning of of_dma_configure():
>
> 	if (!dev->coherent_dma_mask)
> 		dev->coherent_dma_mask = DMA_BIT_MASK(32);
>
> That's more of a nitpick as the values are both the same.
Catalin,

Just posted a patch for size based dma mask with title "of: calculate 
masks of the device based on dma-range size". Please review and comment

--
Murali Karicheri
Linux Kernel, Texas Instruments
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