Subject: [PATCH v2] arm64: pci: add support for pci_mmap_page_range

From: [email-masked] (Jerin Jacob)
Date: Mon, 18 Apr 2016 19:13:57 +0530

On Fri, Apr 15, 2016 at 02:09:53PM +0100, Will Deacon wrote:
> On Thu, Apr 14, 2016 at 02:40:56AM +0530, Jerin Jacob wrote:
> > Certain X11 servers and user space network drivers frameworks
> > need PCI mmaped /sys/bus/pci/devices/B:D:F/resourceX file to
> > access PCI bar address space from user space.
> > 
> > Signed-off-by: Jerin Jacob <[email-masked]>
> > ---
> > Changes in v2:
> >   - Rebased to 4.6.0-rc3.
> >   - Tested and verified the change on Thunderx and xgene1 arm64 platforms
> > 
> >  arch/arm64/include/asm/pci.h |  6 ++++++
> >  arch/arm64/kernel/pci.c      | 20 ++++++++++++++++++++
> >  2 files changed, 26 insertions(+)
> > 
> > diff --git a/arch/arm64/include/asm/pci.h b/arch/arm64/include/asm/pci.h
> > index b9a7ba9..9d7e460 100644
> > --- a/arch/arm64/include/asm/pci.h
> > +++ b/arch/arm64/include/asm/pci.h
> > @@ -37,5 +37,11 @@ static inline int pci_proc_domain(struct pci_bus *bus)
> >  }
> >  #endif  /* CONFIG_PCI */
> >  
> > +#define HAVE_PCI_MMAP
> 
> By defining this symbol, we also get lumbered with the legacy /proc
> interface, which I'd be keen to avoid exposing until we have people
> explicitly asking for it.

AFAIK, /proc/bus/pci/* proc entry files will be created irrespective
of HAVE_PCI_MMAP, But mmap capability added only when HAVE_PCI_MMAP selected.

> 
> Any chance you could expose only the /sysfs interface on arm64?
> 

AFAIK, With existing generic code infrastructure its is not possible.
IMO, Introducing yet another kernel configuration or weak function to disable
in the /proc/ entries in the generic code may not be a good idea.

> > +
> > +extern int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
> > +	enum pci_mmap_state mmap_state, int write_combine);
> > +
> > +
> >  #endif  /* __KERNEL__ */
> >  #endif  /* __ASM_PCI_H */
> > diff --git a/arch/arm64/kernel/pci.c b/arch/arm64/kernel/pci.c
> > index c72de66..be7ddf1 100644
> > --- a/arch/arm64/kernel/pci.c
> > +++ b/arch/arm64/kernel/pci.c
> > @@ -82,3 +82,23 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
> >  	return NULL;
> >  }
> >  #endif
> > +
> > +int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
> > +		enum pci_mmap_state mmap_state, int write_combine)
> > +{
> > +	/*
> > +	* I/O space can be accessed via normal processor loads and stores on
> > +	* this platform but for now we elect not to do this and portable
> > +	* drivers should not do this anyway.
> > +	*/
> > +	if (mmap_state == pci_mmap_io)
> > +		return -EINVAL;
> > +
> > +	if (write_combine)
> > +		vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> > +	else
> > +		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
> 
> For consistency with ioremap, this should be pgprot_device.

Will fix it in v3.

> Will