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dma-mapping: treat dev->bus_dma_mask as a DMA limit

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Using a mask to represent bus DMA constraints has a set of limitations.
The biggest one being it can only hold a power of two (minus one). The
DMA mapping code is already aware of this and treats dev->bus_dma_mask
as a limit. This quirk is already used by some architectures although
still rare.

With the introduction of the Raspberry Pi 4 we've found a new contender
for the use of bus DMA limits, as its PCIe bus can only address the
lower 3GB of memory (of a total of 4GB). This is impossible to represent
with a mask. To make things worse the device-tree code rounds non power
of two bus DMA limits to the next power of two, which is unacceptable in
this case.

In the light of this, rename dev->bus_dma_mask to dev->bus_dma_limit all
over the tree and treat it as such. Note that dev->bus_dma_limit should
contain the higher accessible DMA address.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Nicolas Saenz Julienne
2019-11-21 10:26:44 +01:00
committed by Christoph Hellwig
parent d7293f79ca
commit a7ba70f178
13 changed files with 46 additions and 53 deletions
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27
kernel/dma/direct.c
View File

@@ -27,10 +27,10 @@ static void report_addr(struct device *dev, dma_addr_t dma_addr, size_t size)
{
if (!dev->dma_mask) {
dev_err_once(dev, "DMA map on device without dma_mask\n");
} else if (*dev->dma_mask >= DMA_BIT_MASK(32) || dev->bus_dma_mask) {
} else if (*dev->dma_mask >= DMA_BIT_MASK(32) || dev->bus_dma_limit) {
dev_err_once(dev,
"overflow %pad+%zu of DMA mask %llx bus mask %llx\n",
&dma_addr, size, *dev->dma_mask, dev->bus_dma_mask);
"overflow %pad+%zu of DMA mask %llx bus limit %llx\n",
&dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
}
WARN_ON_ONCE(1);
}
@@ -57,15 +57,14 @@ u64 dma_direct_get_required_mask(struct device *dev)
}
static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
u64 *phys_mask)
u64 *phys_limit)
{
if (dev->bus_dma_mask && dev->bus_dma_mask < dma_mask)
dma_mask = dev->bus_dma_mask;
u64 dma_limit = min_not_zero(dma_mask, dev->bus_dma_limit);
if (force_dma_unencrypted(dev))
*phys_mask = __dma_to_phys(dev, dma_mask);
*phys_limit = __dma_to_phys(dev, dma_limit);
else
*phys_mask = dma_to_phys(dev, dma_mask);
*phys_limit = dma_to_phys(dev, dma_limit);
/*
* Optimistically try the zone that the physical address mask falls
@@ -75,9 +74,9 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
* Note that GFP_DMA32 and GFP_DMA are no ops without the corresponding
* zones.
*/
if (*phys_mask <= DMA_BIT_MASK(zone_dma_bits))
if (*phys_limit <= DMA_BIT_MASK(zone_dma_bits))
return GFP_DMA;
if (*phys_mask <= DMA_BIT_MASK(32))
if (*phys_limit <= DMA_BIT_MASK(32))
return GFP_DMA32;
return 0;
}
@@ -85,7 +84,7 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
{
return phys_to_dma_direct(dev, phys) + size - 1 <=
min_not_zero(dev->coherent_dma_mask, dev->bus_dma_mask);
min_not_zero(dev->coherent_dma_mask, dev->bus_dma_limit);
}
struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
@@ -94,7 +93,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
size_t alloc_size = PAGE_ALIGN(size);
int node = dev_to_node(dev);
struct page *page = NULL;
u64 phys_mask;
u64 phys_limit;
if (attrs & DMA_ATTR_NO_WARN)
gfp |= __GFP_NOWARN;
@@ -102,7 +101,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
/* we always manually zero the memory once we are done: */
gfp &= ~__GFP_ZERO;
gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
&phys_mask);
&phys_limit);
page = dma_alloc_contiguous(dev, alloc_size, gfp);
if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
dma_free_contiguous(dev, page, alloc_size);
@@ -116,7 +115,7 @@ again:
page = NULL;
if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
phys_mask < DMA_BIT_MASK(64) &&
phys_limit < DMA_BIT_MASK(64) &&
!(gfp & (GFP_DMA32 | GFP_DMA))) {
gfp |= GFP_DMA32;
goto again;