[04/15] swiotlb: remove unnecessary swiotlb_bus_to_virt

swiotlb_bus_to_virt is unncessary; we can use swiotlb_bus_to_phys and
phys_to_virt instead.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
---
 arch/powerpc/kernel/dma-swiotlb.c |   10 ----------
 lib/swiotlb.c                     |   34 ++++++++++++++++------------------
 2 files changed, 16 insertions(+), 28 deletions(-)

On Jul 9, 2009, at 8:04 PM, FUJITA Tomonori wrote:

> swiotlb_bus_to_virt is unncessary; we can use swiotlb_bus_to_phys and
> phys_to_virt instead.

phys_to_virt (also, virt_to_phys) is invalid for highmem addresses on  
ppc.  In most of the uses in this file, it doesn't matter, as the  
iotlb buffers themselves are alloc'd out of lowmem, but the  
dma_mark_clean() calls could happen on a highmem addr.  Currently, on  
powerpc, dma_mark_clean() doesn't do anything, so it isn't a  
functional problem.  I'm fine with the bulk of this patch, because in  
reality, if I need to do something with a virtual address of a highmem  
page, I have to get a kmap for the page.  So the existing  
swiotlb_bus_to_virt isn't really helping.

What is dma_mark_clean used for?  Could it be made to take a paddr,  
and let the implementation deal with making sure there's a valid vaddr  
for the actual "clean" operation?

I'd also like to see a comment with swiotlb_virt_to_bus() that notes  
that it should only be called on addresses in lowmem.

Cheers,
Becky

>
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
> ---
> arch/powerpc/kernel/dma-swiotlb.c |   10 ----------
> lib/swiotlb.c                     |   34 +++++++++++++++ 
> +------------------
> 2 files changed, 16 insertions(+), 28 deletions(-)
>
> diff --git a/arch/powerpc/kernel/dma-swiotlb.c b/arch/powerpc/kernel/ 
> dma-swiotlb.c
> index 68ccf11..41534ae 100644
> --- a/arch/powerpc/kernel/dma-swiotlb.c
> +++ b/arch/powerpc/kernel/dma-swiotlb.c
> @@ -24,16 +24,6 @@
> int swiotlb __read_mostly;
> unsigned int ppc_swiotlb_enable;
>
> -void *swiotlb_bus_to_virt(struct device *hwdev, dma_addr_t addr)
> -{
> -	unsigned long pfn = PFN_DOWN(swiotlb_bus_to_phys(hwdev, addr));
> -	void *pageaddr = page_address(pfn_to_page(pfn));
> -
> -	if (pageaddr != NULL)
> -		return pageaddr + (addr % PAGE_SIZE);
> -	return NULL;
> -}
> -
> dma_addr_t swiotlb_phys_to_bus(struct device *hwdev, phys_addr_t  
> paddr)
> {
> 	return paddr + get_dma_direct_offset(hwdev);
> diff --git a/lib/swiotlb.c b/lib/swiotlb.c
> index dc1cd1f..1a89c84 100644
> --- a/lib/swiotlb.c
> +++ b/lib/swiotlb.c
> @@ -130,11 +130,6 @@ static dma_addr_t swiotlb_virt_to_bus(struct  
> device *hwdev,
> 	return swiotlb_phys_to_bus(hwdev, virt_to_phys(address));
> }
>
> -void * __weak swiotlb_bus_to_virt(struct device *hwdev, dma_addr_t  
> address)
> -{
> -	return phys_to_virt(swiotlb_bus_to_phys(hwdev, address));
> -}
> -
> int __weak swiotlb_arch_address_needs_mapping(struct device *hwdev,
> 					       dma_addr_t addr, size_t size)
> {
> @@ -307,9 +302,10 @@ address_needs_mapping(struct device *hwdev,  
> dma_addr_t addr, size_t size)
> 	return swiotlb_arch_address_needs_mapping(hwdev, addr, size);
> }
>
> -static int is_swiotlb_buffer(char *addr)
> +static int is_swiotlb_buffer(phys_addr_t paddr)
> {
> -	return addr >= io_tlb_start && addr < io_tlb_end;
> +	return paddr >= virt_to_phys(io_tlb_start) &&
> +		paddr < virt_to_phys(io_tlb_end);
> }
>
> /*
> @@ -582,11 +578,13 @@ EXPORT_SYMBOL(swiotlb_alloc_coherent);
>
> void
> swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
> -		      dma_addr_t dma_handle)
> +		      dma_addr_t dev_addr)
> {
> +	phys_addr_t paddr = swiotlb_bus_to_phys(hwdev, dev_addr);
> +
> 	WARN_ON(irqs_disabled());
> -	if (!is_swiotlb_buffer(vaddr))
> -		free_pages((unsigned long) vaddr, get_order(size));
> +	if (!is_swiotlb_buffer(paddr))
> +		free_pages((unsigned long)vaddr, get_order(size));
> 	else
> 		/* DMA_TO_DEVICE to avoid memcpy in unmap_single */
> 		do_unmap_single(hwdev, vaddr, size, DMA_TO_DEVICE);
> @@ -671,19 +669,19 @@ EXPORT_SYMBOL_GPL(swiotlb_map_page);
> static void unmap_single(struct device *hwdev, dma_addr_t dev_addr,
> 			 size_t size, int dir)
> {
> -	char *dma_addr = swiotlb_bus_to_virt(hwdev, dev_addr);
> +	phys_addr_t paddr = swiotlb_bus_to_phys(hwdev, dev_addr);
>
> 	BUG_ON(dir == DMA_NONE);
>
> -	if (is_swiotlb_buffer(dma_addr)) {
> -		do_unmap_single(hwdev, dma_addr, size, dir);
> +	if (is_swiotlb_buffer(paddr)) {
> +		do_unmap_single(hwdev, phys_to_virt(paddr), size, dir);
> 		return;
> 	}
>
> 	if (dir != DMA_FROM_DEVICE)
> 		return;
>
> -	dma_mark_clean(dma_addr, size);
> +	dma_mark_clean(phys_to_virt(paddr), size);
> }
>
> void swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
> @@ -708,19 +706,19 @@ static void
> swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
> 		    size_t size, int dir, int target)
> {
> -	char *dma_addr = swiotlb_bus_to_virt(hwdev, dev_addr);
> +	phys_addr_t paddr = swiotlb_bus_to_phys(hwdev, dev_addr);
>
> 	BUG_ON(dir == DMA_NONE);
>
> -	if (is_swiotlb_buffer(dma_addr)) {
> -		sync_single(hwdev, dma_addr, size, dir, target);
> +	if (is_swiotlb_buffer(paddr)) {
> +		sync_single(hwdev, phys_to_virt(paddr), size, dir, target);
> 		return;
> 	}
>
> 	if (dir != DMA_FROM_DEVICE)
> 		return;
>
> -	dma_mark_clean(dma_addr, size);
> +	dma_mark_clean(phys_to_virt(paddr), size);

>
> }
>
> void
> -- 
> 1.6.0.6
>
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On Mon, 13 Jul 2009 21:17:21 -0500
Becky Bruce <beckyb@kernel.crashing.org> wrote:

> 
> On Jul 9, 2009, at 8:04 PM, FUJITA Tomonori wrote:
> 
> > swiotlb_bus_to_virt is unncessary; we can use swiotlb_bus_to_phys and
> > phys_to_virt instead.
> 
> phys_to_virt (also, virt_to_phys) is invalid for highmem addresses on  
> ppc.  In most of the uses in this file, it doesn't matter, as the  
> iotlb buffers themselves are alloc'd out of lowmem,

Right,

> but the  
> dma_mark_clean() calls could happen on a highmem addr.  Currently, on  
> powerpc, dma_mark_clean() doesn't do anything, so it isn't a  
> functional problem.

Oops, I overlooked this. However, as you said, this is not a problem
with the current code.


>  I'm fine with the bulk of this patch, because in  
> reality, if I need to do something with a virtual address of a highmem  
> page, I have to get a kmap for the page.  So the existing  
> swiotlb_bus_to_virt isn't really helping.
> 
> What is dma_mark_clean used for?  Could it be made to take a paddr,  
> and let the implementation deal with making sure there's a valid vaddr  
> for the actual "clean" operation?

I think that it's IA64's optimization (it's a NULL function on X86
like POWERPC). It's defined in arch/ia64/mm/init.c. Looks like POWERPC
could use this optimization, I guess.

dma_mark_clean() just modifies the page flag (what it needs is struct
page) so I think that we can make it take a paddr.


> I'd also like to see a comment with swiotlb_virt_to_bus() that notes  
> that it should only be called on addresses in lowmem.

Ok, I'll do.


Thanks,

On Mon, 2009-07-13 at 21:17 -0500, Becky Bruce wrote:
> 
> phys_to_virt (also, virt_to_phys) is invalid for highmem addresses on  
> ppc. 

I would be surprised if x86 was any different here. Most of our highmem
implementation comes straight from x86 :-)

Cheers,
Ben.