Re: [PATCH v4 3/6] of: fix size when dma-range is not used
From: Murali Karicheri
Date: Wed Jan 28 2015 - 17:15:41 EST
On 01/28/2015 10:45 AM, Rob Herring wrote:
On Wed, Jan 28, 2015 at 5:05 AM, Catalin Marinas
<catalin.marinas@xxxxxxx> wrote:
On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote:
On 01/27/2015 06:27 AM, Robin Murphy wrote:
On 23/01/15 22:32, Murali Karicheri wrote:
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@xxxxxxxxxx>
Cc: Grant Likely<grant.likely@xxxxxxxxxx>
Cc: Rob Herring<robh+dt@xxxxxxxxxx>
Cc: Bjorn Helgaas<bhelgaas@xxxxxxxxxx>
Cc: Will Deacon<will.deacon@xxxxxxx>
Cc: Russell King<linux@xxxxxxxxxxxxxxxx>
Cc: Arnd Bergmann<arnd@xxxxxxxx>
Cc: Suravee Suthikulpanit<Suravee.Suthikulpanit@xxxxxxx>
Signed-off-by: Murali Karicheri<m-karicheri2@xxxxxx>
---
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
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;
}
In of_dma_configure(), we currently assume that the default coherent
mask is 32-bit. In this thread:
http://article.gmane.org/gmane.linux.kernel/1835096
we talked about setting the coherent mask based on size automatically.
I'm not sure about the size but I think we can assume is 32-bit mask + 1
if it is not specified in the DT. Instead of just assuming a default
mask, let's assume a default size and create the mask based on this
(untested):
diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index 5b33c6a21807..9ff8d1286b44 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c
@@ -170,10 +170,10 @@ static void of_dma_configure(struct device *dev)
struct iommu_ops *iommu;
/*
- * Set default dma-mask to 32 bit. Drivers are expected to setup
- * the correct supported dma_mask.
+ * Set default size to cover the 32-bit. Drivers are expected to setup
+ * the correct size and dma_mask.
*/
- dev->coherent_dma_mask = DMA_BIT_MASK(32);
+ size = 1ULL<< 32;
/*
* Set it to coherent_dma_mask by default if the architecture
@@ -185,13 +185,24 @@ static void of_dma_configure(struct device *dev)
ret = of_dma_get_range(dev->of_node,&dma_addr,&paddr,&size);
if (ret< 0) {
dma_addr = offset = 0;
- size = dev->coherent_dma_mask;
Are we assuming dma_addr, paddr and size are not touched on error? If
so, we can get rid of this clause entirely.
Checking the code for of_dma_get_range() I see paddr is modified on
error case, but is used only for success case in this function. dma_addr
and size are not modified. So setting dma_addr and offset to zero before
hand like size might work as below
dma_addr = offset = 0;
size = 1ULL << 32;
ret = of_dma_get_range(dev->of_node,&dma_addr,&paddr,&size);
if (!ret) {
offset = PFN_DOWN(paddr - dma_addr);
}
.. rest of the code.
Murali
} else {
offset = PFN_DOWN(paddr - dma_addr);
dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", dev->dma_pfn_offset);
}
dev->dma_pfn_offset = offset;
+ /*
+ * Workaround for DTs setting the size to a mask or 0.
+ */
+ if (is_power_of_2(size + 1))
+ size += 1;
As I mentioned, I think power of 2 is too restrictive (from a DT
perspective even though the kernel may require a power of 2 here for
the mask). Just checking bit0 set should be enough.
Also, we need a WARN here so DTs get fixed.
+
+ /*
+ * Coherent DMA masks larger than 32-bit must be explicitly set by the
+ * driver.
+ */
+ dev->coherent_dma_mask = min(DMA_BIT_MASK(32), DMA_BIT_MASK(ilog2(size)));
+
coherent = of_dma_is_coherent(dev->of_node);
dev_dbg(dev, "device is%sdma coherent\n",
coherent ? " " : " not ");
--
Catalin
--
Murali Karicheri
Linux Kernel, Texas Instruments
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