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Commit e24c2d96 authored by David S. Miller's avatar David S. Miller Committed by Greg Kroah-Hartman
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[PATCH] PCI: DMA bursting advice 



After seeing, at best, "guesses" as to the following kind
of information in several drivers, I decided that we really
need a way for platforms to specifically give advice in this
area for what works best with their PCI controller implementation.

Basically, this new interface gives DMA bursting advice on
PCI.  There are three forms of the advice:

1) Burst as much as possible, it is not necessary to end bursts
   on some particular boundary for best performance.

2) Burst on some byte count multiple.  A DMA burst to some multiple of
   number of bytes may be done, but it is important to end the burst
   on an exact multiple for best performance.

   The best example of this I am aware of are the PPC64 PCI
   controllers, where if you end a burst mid-cacheline then
   chip has to refetch the data and the IOMMU translations
   which hurts performance a lot.

3) Burst on a single byte count multiple.  Bursts shall end
   exactly on the next multiple boundary for best performance.

   Sparc64 and Alpha's PCI controllers operate this way.  They
   disconnect any device which tries to burst across a cacheline
   boundary.

   Actually, newer sparc64 PCI controllers do not have this behavior.
   That is why the "pdev" is passed into the interface, so I can
   add code later to check which PCI controller the system is using
   and give advice accordingly.

Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 2311b1f2

include/asm-alpha/pci.h

+17 −0
Original line number Diff line number Diff line
@@ -223,6 +223,23 @@ pci_dac_dma_sync_single_for_device(struct pci_dev *pdev, dma64_addr_t dma_addr, 
	/* Nothing to do. */

}



static inline void pci_dma_burst_advice(struct pci_dev *pdev,

					enum pci_dma_burst_strategy *strat,

					unsigned long *strategy_parameter)

{

	unsigned long cacheline_size;

	u8 byte;



	pci_read_config_byte(pdev, PCI_CACHE_LINE_SIZE, &byte);

	if (byte == 0)

		cacheline_size = 1024;

	else

		cacheline_size = (int) byte * 4;



	*strat = PCI_DMA_BURST_BOUNDARY;

	*strategy_parameter = cacheline_size;

}



/* TODO: integrate with include/asm-generic/pci.h ? */

static inline int pci_get_legacy_ide_irq(struct pci_dev *dev, int channel)

{

include/asm-arm/pci.h

+8 −0
Original line number Diff line number Diff line
@@ -42,6 +42,14 @@ static inline void pcibios_penalize_isa_irq(int irq) 
#define pci_unmap_len(PTR, LEN_NAME)		((PTR)->LEN_NAME)

#define pci_unmap_len_set(PTR, LEN_NAME, VAL)	(((PTR)->LEN_NAME) = (VAL))



static inline void pci_dma_burst_advice(struct pci_dev *pdev,

					enum pci_dma_burst_strategy *strat,

					unsigned long *strategy_parameter)

{

	*strat = PCI_DMA_BURST_INFINITY;

	*strategy_parameter = ~0UL;

}



#define HAVE_PCI_MMAP

extern int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,

                               enum pci_mmap_state mmap_state, int write_combine);

include/asm-frv/pci.h

+8 −0
Original line number Diff line number Diff line
@@ -57,6 +57,14 @@ extern void pci_free_consistent(struct pci_dev *hwdev, size_t size, 
 */

#define PCI_DMA_BUS_IS_PHYS	(1)



static inline void pci_dma_burst_advice(struct pci_dev *pdev,

					enum pci_dma_burst_strategy *strat,

					unsigned long *strategy_parameter)

{

	*strat = PCI_DMA_BURST_INFINITY;

	*strategy_parameter = ~0UL;

}



/*

 *	These are pretty much arbitary with the CoMEM implementation.

 *	We have the whole address space to ourselves.

include/asm-i386/pci.h

+8 −0
Original line number Diff line number Diff line
@@ -99,6 +99,14 @@ static inline void pcibios_add_platform_entries(struct pci_dev *dev) 
{

}



static inline void pci_dma_burst_advice(struct pci_dev *pdev,

					enum pci_dma_burst_strategy *strat,

					unsigned long *strategy_parameter)

{

	*strat = PCI_DMA_BURST_INFINITY;

	*strategy_parameter = ~0UL;

}



#endif /* __KERNEL__ */



/* implement the pci_ DMA API in terms of the generic device dma_ one */

include/asm-ia64/pci.h

+17 −0
Original line number Diff line number Diff line
@@ -82,6 +82,23 @@ extern int pcibios_prep_mwi (struct pci_dev *); 
#define sg_dma_len(sg)		((sg)->dma_length)

#define sg_dma_address(sg)	((sg)->dma_address)



static inline void pci_dma_burst_advice(struct pci_dev *pdev,

					enum pci_dma_burst_strategy *strat,

					unsigned long *strategy_parameter)

{

	unsigned long cacheline_size;

	u8 byte;



	pci_read_config_byte(pdev, PCI_CACHE_LINE_SIZE, &byte);

	if (byte == 0)

		cacheline_size = 1024;

	else

		cacheline_size = (int) byte * 4;



	*strat = PCI_DMA_BURST_MULTIPLE;

	*strategy_parameter = cacheline_size;

}



#define HAVE_PCI_MMAP

extern int pci_mmap_page_range (struct pci_dev *dev, struct vm_area_struct *vma,

				enum pci_mmap_state mmap_state, int write_combine);