Re: [PATCH] of: calculate masks of the device based on dma-range size

[Murali Karicheri]

On 02/09/2015 06:27 AM, Catalin Marinas wrote:
> On Fri, Feb 06, 2015 at 03:15:20PM -0500, Murali Karicheri wrote:
> > diff --git a/drivers/of/device.c b/drivers/of/device.c
> > index 314c8a9..44209fa 100644
> > --- a/drivers/of/device.c
> > +++ b/drivers/of/device.c
> > @@ -83,17 +83,18 @@ int of_device_add(struct platform_device *ofdev)
> >    */
> >   void of_dma_configure(struct device *dev, struct device_node *np)
> >   {
> > -	u64 dma_addr, paddr, size;
> > +	u64 dma_addr = 0, paddr, size;
> >   	int ret;
> >   	bool coherent;
> > -	unsigned long offset;
> > +	unsigned long offset = 0;
> >   	struct iommu_ops *iommu;
> >
> >   	/*
> >   	 * Set default dma-mask to 32 bit. Drivers are expected to setup
> >   	 * the correct supported dma_mask.
> >   	 */
> > -	dev->coherent_dma_mask = DMA_BIT_MASK(32);
> > +	if (!dev->coherent_dma_mask)
> > +		dev->coherent_dma_mask = DMA_BIT_MASK(32);
> >
> >   	/*
> >   	 * Set it to coherent_dma_mask by default if the architecture
> > @@ -102,11 +103,14 @@ void of_dma_configure(struct device *dev, struct device_node *np)
> >   	if (!dev->dma_mask)
> >   		dev->dma_mask =&dev->coherent_dma_mask;
> >
> > +	/*
> > +	 * Set default size to cover the 32-bit. Drivers are expected to setup
> > +	 * the correct size and dma_mask.
> > +	 */
>
> Nitpick: drivers don't set up the size, just the mask. We read the size
> from DT.

Not sure how this came, I will update this.
> > +	size = 1ULL<<  32;
> > +
> >   	ret = of_dma_get_range(np,&dma_addr,&paddr,&size);
> > -	if (ret<  0) {
> > -		dma_addr = offset = 0;
> > -		size = dev->coherent_dma_mask + 1;
>
> Do you assume that, on error, of_dma_get_range() does not touch any of
> the dma_addr/paddr/size? It looks safer to me to leave it as the
> original.
I think dma_addr and paddr is both modified on error. So this change 
can't be done. I will revert the logic back to original.
> > -	} else {
> > +	if (!ret) {
> >   		offset = PFN_DOWN(paddr - dma_addr);
> >
> >   		/*
> > @@ -128,6 +132,15 @@ void of_dma_configure(struct device *dev, struct device_node *np)
> >
> >   	dev->dma_pfn_offset = offset;
> >
> > +	/*
> > +	 * Limit coherent and dma mask based on size and default mask
> > +	 * set by the driver.
> > +	 */
> > +	dev->coherent_dma_mask = min(dev->coherent_dma_mask,
> > +				     DMA_BIT_MASK(ilog2(dma_addr + size)));
>
> Do we need to cover the case where size is incorrectly set to 0 in the
> DT? At least some warning and leaving the mask unchanged.

The previous series already warn and return if the size is incorrect 
(Patch v6 3/7) and leave the dma mask unchanged. So we don't have to do 
anything in this patch. I will fix the above and re-send.
> > +	*dev->dma_mask = min((*dev->dma_mask),
> > +			     DMA_BIT_MASK(ilog2(dma_addr + size)));
> > +
> >   	coherent = of_dma_is_coherent(np);
> >   	dev_dbg(dev, "device is%sdma coherent\n",
> >   		coherent ? " " : " not ");


--
Murali Karicheri
Linux Kernel, Texas Instruments
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