On Thu, Sep 10, 2020 at 07:02:23PM +0100, Robin Murphy wrote:

On 2020-09-10 06:40, Christoph Hellwig wrote:

quoted

Move the helpers to translate to and from direct mapping DMA addresses
to dma-direct.h.  This not only is the most logical place, but the new
placement also avoids dependency loops with pending commits.

For the straightforward move as it should be,

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

However I do wonder how much of this could be cleaned up further...

quoted

+
+#ifdef __arch_page_to_dma
+#error Please update to __arch_pfn_to_dma
+#endif

This must be long, long dead by now.

Yeah.  I had a patch to remove this which lead me into the rabbit
hole your described later.  A few patches in I decided to give up
and just do the trivial move.  But it probably makes sense to pick
up at least the two trivial dead code removal patches..

quoted

+static inline unsigned long dma_to_pfn(struct device *dev, dma_addr_t addr)
+{
+	unsigned long pfn = __bus_to_pfn(addr);
+
+	if (dev)
+		pfn += dev->dma_pfn_offset;
+
+	return pfn;
+}

These are only overridden for OMAP1510, and it looks like it wouldn't take 
much for the platform code or ohci-omap driver to set up a generic DMA 
offset for the relevant device.

I sent a ping to the omap maintainers earlier this week to ask for that :)

quoted

+static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
+{
+	if (dev)
+		return pfn_to_dma(dev, virt_to_pfn(addr));
+
+	return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
+}

And this is only used for some debug prints in dmabounce.

Similarly the __bus_to_*()/__*_to_bus() calls themselves only appear 
significant to mach-footbridge any more, and could probably also be evolved 
into regular DMA offsets now that all API calls must have a non-NULL 
device. I think I might come back and take a closer look at all this at 
some point in future... :)

Yes,  pretty much all of this should eventually go away.  I just don't
want to bock the ranges work on all kinds of random arm cleanups..