Re: [PATCH v5 06/14] drivers: acpi: implement acpi_dma_configure

[Lorenzo Pieralisi]

On Tue, Sep 13, 2016 at 03:41:06PM +0100, Robin Murphy wrote:
> On 09/09/16 15:23, Lorenzo Pieralisi wrote:
> > On DT based systems, the of_dma_configure() API implements DMA
> > configuration for a given device. On ACPI systems an API equivalent to
> > of_dma_configure() is missing which implies that it is currently not
> > possible to set-up DMA operations for devices through the ACPI generic
> > kernel layer.
> > 
> > This patch fills the gap by introducing acpi_dma_configure/deconfigure()
> > calls that for now are just wrappers around arch_setup_dma_ops() and
> > arch_teardown_dma_ops() and also updates ACPI and PCI core code to use
> > the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions.
> > 
> > The DMA range size passed to arch_setup_dma_ops() is sized according
> > to the device coherent_dma_mask (starting at address 0x0), mirroring the
> > DT probing path behaviour when a dma-ranges property is not provided
> > for the device being probed; this changes the current arch_setup_dma_ops()
> > call parameters in the ACPI probing case, but since arch_setup_dma_ops()
> > is a NOP on all architectures but ARM/ARM64 this patch does not change
> > the current kernel behaviour on them.
> > 
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> [pci]
> > Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Cc: Robin Murphy <robin.murphy@xxxxxxx>
> > Cc: Tomasz Nowicki <tn@xxxxxxxxxxxx>
> > Cc: Joerg Roedel <joro@xxxxxxxxxx>
> > Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> > ---
> >  drivers/acpi/glue.c     |  4 ++--
> >  drivers/acpi/scan.c     | 24 ++++++++++++++++++++++++
> >  drivers/pci/probe.c     |  3 +--
> >  include/acpi/acpi_bus.h |  2 ++
> >  include/linux/acpi.h    |  5 +++++
> >  5 files changed, 34 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
> > index 5ea5dc2..f8d6564 100644
> > --- a/drivers/acpi/glue.c
> > +++ b/drivers/acpi/glue.c
> > @@ -227,8 +227,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
> >  
> >  	attr = acpi_get_dma_attr(acpi_dev);
> >  	if (attr != DEV_DMA_NOT_SUPPORTED)
> > -		arch_setup_dma_ops(dev, 0, 0, NULL,
> > -				   attr == DEV_DMA_COHERENT);
> > +		acpi_dma_configure(dev, attr);

Here's the call for non-PCI devices ;-)

> >  	acpi_physnode_link_name(physical_node_name, node_id);
> >  	retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,
> > @@ -251,6 +250,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
> >  	return 0;
> >  
> >   err:
> > +	acpi_dma_deconfigure(dev);
> >  	ACPI_COMPANION_SET(dev, NULL);
> >  	put_device(dev);
> >  	put_device(&acpi_dev->dev);
> > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > index e878fc7..9614232 100644
> > --- a/drivers/acpi/scan.c
> > +++ b/drivers/acpi/scan.c
> > @@ -1370,6 +1370,30 @@ enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
> >  		return DEV_DMA_NON_COHERENT;
> >  }
> >  
> > +/**
> > + * acpi_dma_configure - Set-up DMA configuration for the device.
> > + * @dev: The pointer to the device
> > + * @attr: device dma attributes
> > + */
> > +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
> > +{
> > +	/*
> > +	 * Assume dma valid range starts at 0 and covers the whole
> > +	 * coherent_dma_mask.
> > +	 */
> > +	arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, NULL,
> > +			   attr == DEV_DMA_COHERENT);
> 
> This looks a bit hairy - if we're setting up the DMA configuration at
> this point can we really always rely on the device already having a
> valid DMA mask? I think it would make sense to at least check, and apply
> the standard default 32-bit mask  if not.

That's a good point, but we would be changing the x86/IA64 probing path
if we do what you suggest; so I think you are right and it should be a
safe change to make but I still need to make sure we do not break
anything in the process.

> > +}
> > +
> > +/**
> > + * acpi_dma_deconfigure - Tear-down DMA configuration for the device.
> > + * @dev: The pointer to the device
> > + */
> > +void acpi_dma_deconfigure(struct device *dev)
> > +{
> > +	arch_teardown_dma_ops(dev);
> > +}
> 
> As touched upon in the dwc-usb3 thread, is it worth exporting these for
> the benefit of modular bus/glue code, to match of_dma_configure()?

I think yes, I will do.

> >  static void acpi_init_coherency(struct acpi_device *adev)
> >  {
> >  	unsigned long long cca = 0;
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 93f280d..e96d482 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -1734,8 +1734,7 @@ static void pci_dma_configure(struct pci_dev *dev)
> >  		if (attr == DEV_DMA_NOT_SUPPORTED)
> >  			dev_warn(&dev->dev, "DMA not supported.\n");
> >  		else
> > -			arch_setup_dma_ops(&dev->dev, 0, 0, NULL,
> > -					   attr == DEV_DMA_COHERENT);
> > +			acpi_dma_configure(&dev->dev, attr);
> >  	}
> 
> What about non-PCI stuff? I see there's at least an
> acpi_create_platform_device() which I'd also kind of expect to see as a
> caller (which indeed might also tie in with the aforementioned default
> mask initialisation).

See above (acpi_bind_one()).

Thanks for having a look,
Lorenzo

> 
> Robin.
> 
> >  
> >  	pci_put_host_bridge_device(bridge);
> > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> > index c1a524d..4242c31 100644
> > --- a/include/acpi/acpi_bus.h
> > +++ b/include/acpi/acpi_bus.h
> > @@ -573,6 +573,8 @@ struct acpi_pci_root {
> >  
> >  bool acpi_dma_supported(struct acpi_device *adev);
> >  enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev);
> > +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr);
> > +void acpi_dma_deconfigure(struct device *dev);
> >  
> >  struct acpi_device *acpi_find_child_device(struct acpi_device *parent,
> >  					   u64 address, bool check_children);
> > diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> > index c5eaf2f..05d4e48 100644
> > --- a/include/linux/acpi.h
> > +++ b/include/linux/acpi.h
> > @@ -729,6 +729,11 @@ static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
> >  	return DEV_DMA_NOT_SUPPORTED;
> >  }
> >  
> > +static inline void acpi_dma_configure(struct device *dev,
> > +				      enum dev_dma_attr attr) { }
> > +
> > +static inline void acpi_dma_deconfigure(struct device *dev) { }
> > +
> >  #define ACPI_PTR(_ptr)	(NULL)
> >  
> >  static inline void acpi_device_set_enumerated(struct acpi_device *adev)
> > 
> 
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