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Message-ID: <54C91DC3.4020101@ti.com>
Date: Wed, 28 Jan 2015 12:34:59 -0500
From: Murali Karicheri <m-karicheri2@...com>
To: Rob Herring <robherring2@...il.com>
CC: Catalin Marinas <catalin.marinas@....com>,
Robin Murphy <Robin.Murphy@....com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Russell King <linux@....linux.org.uk>,
Arnd Bergmann <arnd@...db.de>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
Joerg Roedel <joro@...tes.org>,
Will Deacon <Will.Deacon@....com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"grant.likely@...aro.org" <grant.likely@...aro.org>,
"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
Rob Herring <robh+dt@...nel.org>,
"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 3/6] of: fix size when dma-range is not used
On 01/28/2015 10:45 AM, Rob Herring wrote:
> On Wed, Jan 28, 2015 at 5:05 AM, Catalin Marinas
> <catalin.marinas@....com> 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@...tes.org>
>>>>> Cc: Grant Likely<grant.likely@...aro.org>
>>>>> Cc: Rob Herring<robh+dt@...nel.org>
>>>>> Cc: Bjorn Helgaas<bhelgaas@...gle.com>
>>>>> Cc: Will Deacon<will.deacon@....com>
>>>>> Cc: Russell King<linux@....linux.org.uk>
>>>>> Cc: Arnd Bergmann<arnd@...db.de>
>>>>> Cc: Suravee Suthikulpanit<Suravee.Suthikulpanit@....com>
>>>>>
>>>>> Signed-off-by: Murali Karicheri<m-karicheri2@...com>
>>>>> ---
>>>>> 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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