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Message-ID: <54CBC823.3020905@ti.com>
Date: Fri, 30 Jan 2015 13:06:27 -0500
From: Murali Karicheri <m-karicheri2@...com>
To: Catalin Marinas <catalin.marinas@....com>
CC: 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 12:30 PM, Catalin Marinas wrote:
> On Wed, Jan 28, 2015 at 03:55:57PM +0000, Robin Murphy wrote:
>> On 28/01/15 11:05, Catalin Marinas wrote:
>>> On Tue, Jan 27, 2015 at 06:55:15PM +0000, Murali Karicheri wrote:
>>>> 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;
>>> } 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;
>>
>> In fact, since the ilog2 below ends up effectively rounding down, we
>> might as well do away with this check as well and just add 1
>> unconditionally. The only time it makes any difference is when we want
>> it to anyway!
>
> Well, we could simply ignore the is_power_of_2() check but without
> incrementing size as we don't know what arch_setup_dma_ops() does with
> it.
>
> I think we can remove this check altogether (we leaved without it for a
> while) but we need to add 1 when calculating the mask:
>
> dev->coherent_dma_mask = min(DMA_BIT_MASK(32),
> DMA_BIT_MASK(ilog2(size + 1)));
>
For Keystone, the dma_addr is to be taken care as well to determine the
mask. The above will not work.
Based on the discussion so far, this is the function I have come up with
incorporating the suggestions. Please review this and see if I have
missed out any. This works fine on Keystone.
void of_dma_configure(struct device *dev, struct device_node *np)
{
u64 dma_addr = 0, paddr, size;
int ret;
bool coherent;
unsigned long offset = 0;
struct iommu_ops *iommu;
/*
* Set default size to cover the 32-bit. Drivers are expected to setup
* the correct size and dma_mask.
*/
size = 1ULL << 32;
ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
if (!ret) {
offset = PFN_DOWN(paddr - dma_addr);
if (!size) {
dev_err(dev, "Invalid size (%llx)\n",
size);
return;
}
if (size & 1) {
size = size + 1;
dev_warn(dev, "Incorrect usage of size (%llx)\n",
size);
}
dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
}
dev->dma_pfn_offset = offset;
/*
* 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(dma_addr + size)));
/*
* Set dma_mask to coherent_dma_mask by default if the architecture
* code has not set it.
*/
if (!dev->dma_mask)
dev->dma_mask = &dev->coherent_dma_mask;
coherent = of_dma_is_coherent(np);
dev_dbg(dev, "device is%sdma coherent\n",
coherent ? " " : " not ");
iommu = of_iommu_configure(dev, np);
dev_dbg(dev, "device is%sbehind an iommu\n",
iommu ? " " : " not ");
arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent);
}
--
Murali Karicheri
Linux Kernel, Texas Instruments
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