Hi Kumar,
On 21 October 2014 12:08, Kumar Gala <ga...@codeaurora.org> wrote:
>
> On Oct 21, 2014, at 7:56 AM, Ankit Jindal <ankit.jin...@linaro.org> wrote:
>
>> Currently, three types of mem regions are supported: UIO_MEM_PHYS,
>> UIO_MEM_LOGICAL and UIO_MEM_VIRTUAL. Among these UIO_MEM_PHYS helps
>> UIO driver export physcial memory to user space as non-cacheable
>> user memory. Typcially memory-mapped registers of a device are exported
>> to user space as UIO_MEM_PHYS type mem region. The UIO_MEM_PHYS type
>> is not efficient if dma-capable devices are capable of maintaining coherency
>> with CPU caches.
>>
>> This patch adds new type UIO_MEM_PHYS_CACHE for mem regions to enable
>> cacheable access to physical memory from user space.
>>
>> Signed-off-by: Ankit Jindal <ankit.jin...@linaro.org>
>> Signed-off-by: Tushar Jagad <tushar.ja...@linaro.org>
>> ---
>> drivers/uio/uio.c | 11 ++++++++---
>> include/linux/uio_driver.h | 1 +
>> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> Rather than adding a new type, why not allow the driver to set the pgprot
> value, this way one has full control and we don’t need to keep adding types
> for various different cache attributions in the future.
Do you mean to add a new field pgprot_t in the memtype structure and
uio_mmap_physical will set vma->vm_page_prot to this value provided by
driver ? If this is the case then we will need to change all the
current uio based drivers which was the reason I preferred to have a
new mem type.
Please let me know if I have misunderstood anything.
Thanks,
Ankit
>
> - k
>
>>
>> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
>> index 97e6444..120a84b 100644
>> --- a/drivers/uio/uio.c
>> +++ b/drivers/uio/uio.c
>> @@ -644,7 +644,7 @@ static const struct vm_operations_struct
>> uio_physical_vm_ops = {
>> #endif
>> };
>>
>> -static int uio_mmap_physical(struct vm_area_struct *vma)
>> +static int uio_mmap_physical(struct vm_area_struct *vma, bool cacheable)
>> {
>> struct uio_device *idev = vma->vm_private_data;
>> int mi = uio_find_mem_index(vma);
>> @@ -659,7 +659,9 @@ static int uio_mmap_physical(struct vm_area_struct *vma)
>> return -EINVAL;
>>
>> vma->vm_ops = &uio_physical_vm_ops;
>> - vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>> +
>> + if (!cacheable)
>> + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
>>
>> /*
>> * We cannot use the vm_iomap_memory() helper here,
>> @@ -707,10 +709,13 @@ static int uio_mmap(struct file *filep, struct
>> vm_area_struct *vma)
>>
>> switch (idev->info->mem[mi].memtype) {
>> case UIO_MEM_PHYS:
>> - return uio_mmap_physical(vma);
>> + return uio_mmap_physical(vma, false);
>> case UIO_MEM_LOGICAL:
>> case UIO_MEM_VIRTUAL:
>> return uio_mmap_logical(vma);
>> + case UIO_MEM_PHYS_CACHE:
>> + return uio_mmap_physical(vma, true);
>> +
>> default:
>> return -EINVAL;
>> }
>> diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h
>> index 1ad4724..40ca3f3 100644
>> --- a/include/linux/uio_driver.h
>> +++ b/include/linux/uio_driver.h
>> @@ -118,6 +118,7 @@ extern void uio_event_notify(struct uio_info *info);
>> #define UIO_MEM_PHYS 1
>> #define UIO_MEM_LOGICAL 2
>> #define UIO_MEM_VIRTUAL 3
>> +#define UIO_MEM_PHYS_CACHE 4
>>
>> /* defines for uio_port->porttype */
>> #define UIO_PORT_NONE 0
>> --
>> 1.7.9.5
>>
>> --
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>
> --
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> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
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