Re: [V5 PATCH 1/5] ACPI / scan: Parse _CCA and setup device coherency

[Suravee Suthikulanit]

On 5/22/2015 8:25 PM, Rafael J. Wysocki wrote:
> On Friday, May 22, 2015 07:15:17 PM Suravee Suthikulanit wrote:
> > On 5/22/2015 6:05 PM, Rafael J. Wysocki wrote:
> > > On Friday, May 22, 2015 05:24:15 PM Suravee Suthikulanit wrote:
> > > > Not sure if this went out earlier. So I am resending.
> > > >
> > > > On 5/22/15 16:56, Rafael J. Wysocki wrote:
> > > > > > diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
> > > > > > > index 39c485b..b9657af 100644
> > > > > > > --- a/drivers/acpi/glue.c
> > > > > > > +++ b/drivers/acpi/glue.c
> > > > > > > @@ -13,6 +13,7 @@
> > > > > > >    #include <linux/slab.h>
> > > > > > >    #include <linux/rwsem.h>
> > > > > > >    #include <linux/acpi.h>
> > > > > > > +#include <linux/dma-mapping.h>
> > > > > > >
> > > > > > >    #include "internal.h"
> > > > > > >
> > > > > > > @@ -167,6 +168,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
> > > > > > >    	struct list_head *physnode_list;
> > > > > > >    	unsigned int node_id;
> > > > > > >    	int retval = -EINVAL;
> > > > > > > +	bool coherent;
> > > > > > >
> > > > > > >    	if (has_acpi_companion(dev)) {
> > > > > > >    		if (acpi_dev) {
> > > > > > > @@ -223,6 +225,9 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
> > > > > > >    	if (!has_acpi_companion(dev))
> > > > > > >    		ACPI_COMPANION_SET(dev, acpi_dev);
> > > > > > >
> > > > > > > +	if (acpi_check_dma(acpi_dev, &coherent))
> > > > > > > +		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
> > > > > > > +
> > > > > Well, so is this going to work for PCI too after all?
> > > >
> > > > No, as Bjorn suggested, PCI changes for setting DMA coherent from _CCA
> > > > (patch 3/6 in V4) will be submitted separately. We are working on
> > > > cleaning up and up-streaming the PCI ACPI support for ARM64.
> > >
> > > OK, but acpi_bind_one() is called for PCI devices too.  Won't that be a problem?
> >   >
> > In this case, we would be going through the following call path:
> >
> >     --> pci_device_add()
> >      |--> pci_dma_configure() ** 1 **
> >      |--> device_add()
> >        |--> platform_notify()
> >          |--> acpi_platform_notify()
> >           |--> acpi_bind_one() ** 2 **
> >
> > At (1), we would be calling arch_setup_dma_ops() with the PCI host
> > bridge _CCA information. So, it should have already taken care of
> > setting up device coherency here.
> >
> > At (2), if there is no acpi_dev for endpoint devices (which I believe
> > this is normally the case), it would return early and skip
> > arch_setup_dma_ops().
>
> That's not correct.  There may be ACPI companions for endpoint devices too.

Ok. Duly noted :)

> > At (2), if there is an acpi_dev, the coherent_dma flag should have
> > already been setup by the acpi_init_device_object during ACPI scan.
>
> That one sets the flag for the *ACPI* *companion* of the device, which
> I'm still thinking is pointless, isn't it?

When you say pointless, are you referring to the part where we are end 
up calling arch_setup_dma_coherent() twice in this case? I am not quite 
following your point.

> > However, I am not certain about this case since I don't have the DSDT
> > containing  PCI endpoint devices to test with.
>
> Every x86 PC has them (as far as I can say), but in that case there's no
> _CCA and they are all coherent.

Ok.

Thanks,
Suravee


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