On 01/27/2015 06:27 AM, Robin Murphy wrote:

Hi Murali,

On 23/01/15 22:32, Murali Karicheri wrote:

quoted

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. To detect
overflow when mask is set to max of u64, add a check, log error and
return.
Some platform use mask format for size in DTS. So add a work around to
catch this and fix.

Cc: Joerg Roedel <joro@8bytes.org>
Cc: Grant Likely <redacted>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Will Deacon <redacted>
Cc: Russell King <redacted>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>

Signed-off-by: Murali Karicheri <redacted>
---
drivers/of/device.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/of/device.c b/drivers/of/device.c
index 2de320d..0a5ff54 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c

@@ -105,12 +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)
+ size = size + 1;
dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
}

+ /* if size is 0, we have an overflow of u64 */
+ if (!size) {
+ dev_err(dev, "invalid size\n");
+ return;
+ }
+

This seems potentially fragile to dodgy DTs given that we might also be
using size to make a mask later. Would it make sense to double-up a
sanity check as mask-format detection? Something like:

if is_power_of_2(size)
// use size
else if is_power_of_2(size + 1)
// use size + 1
else
// cry

Robin,

How about having the logic like this?

	ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
	if (ret < 0) {
		dma_addr = offset = 0;
		size = dev->coherent_dma_mask + 1;
	} else {
		offset = PFN_DOWN(paddr - dma_addr);
		dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
	}

	if (is_power_of_2(size + 1))
		size = size + 1;
	else if (!is_power_of_2(size))
	{
		dev_err(dev, "invalid size\n");
		return;
	}

Murali

Robin.

quoted

dev->dma_pfn_offset = offset;

coherent = of_dma_is_coherent(np);

-- 
Murali Karicheri
Linux Kernel, Texas Instruments