Re: [PATCH 6/6] dma-mapping: introduce DMA range map, supplanting dma_pfn_offset

On Mon, Sep 14, 2020 at 05:01:47PM -0600, Mathieu Poirier wrote:

[700 lines of the fullquote deleted..]

quoted

+	for (r = map; r->size; r++)
+		num_ranges++;
+
+	new_map = kmemdup(map, array_size(num_ranges + 1, sizeof(*map)),
+			  GFP_KERNEL);
+	if (!new_map)
+		return -ENOMEM;
+	to->dma_range_map = new_map;
+	return 0;
+}
+

This patch seemed Ok to me but it broke the stm32 remoteproc implementation.  When
I tested things out function dma_coerce_mask_and_cohenrent() returns -5 and the
rest of the initialisation fails.  I isolated things to function dma_to_pfn()
[2].  In the original implementation __bus_to_pfn() returns 0xfffff and
dev->dma_pfn_offset is equal to 0x38000.  As such the function returns 0x137fff
and dma_supported() a non-zero value[3].

With this set function dma_to_pfn() received a face lift.  Function
__bus_to_pfn() still returns 0xfffff but translate_dma_to_phys() returns 0,
which forces dma_supported() to also return 0 and that is where the -5 (-EIO)
comes from.

Taking a futher look at translate_dma_to_phy(), @dma_addr never falls within the
bus_dma_region ranges and returns 0.

I'm suspecting an initialisation problem and if it occurred here, it will
likely show up elsewhere.

Can you try this incremental patch?

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index 088c97181ab146..c6b21acba7a459 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h

@@ -46,7 +46,7 @@ static inline phys_addr_t translate_dma_to_phys(struct device *dev,
 		if (dma_addr >= m->dma_start && dma_addr - m->dma_start < m->size)
 			return (phys_addr_t)dma_addr + m->offset;
 
-	return 0;
+	return (phys_addr_t)-1;
 }
 
 #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA

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