RE: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-mc

[Makarand Pawagi]

> -----Original Message-----
> From: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Sent: Tuesday, January 28, 2020 4:39 PM
> To: Makarand Pawagi <makarand.pawagi@xxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; linux@xxxxxxxxxxxxxxx;
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> Subject: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-mc
> 
> Caution: EXT Email
> 
> On Tue, Jan 28, 2020 at 01:38:45PM +0530, Makarand Pawagi wrote:
> > ACPI support is added in the fsl-mc driver. Driver will parse MC DSDT
> > table to extract memory and other resorces.
> >
> > Interrupt (GIC ITS) information will be extracted from MADT table by
> > drivers/irqchip/irq-gic-v3-its-fsl-mc-msi.c.
> >
> > IORT table will be parsed to configure DMA.
> >
> > Signed-off-by: Makarand Pawagi <makarand.pawagi@xxxxxxx>
> > ---
> >  drivers/acpi/arm64/iort.c                   | 53 +++++++++++++++++++++
> >  drivers/bus/fsl-mc/dprc-driver.c            |  3 +-
> >  drivers/bus/fsl-mc/fsl-mc-bus.c             | 48 +++++++++++++------
> >  drivers/bus/fsl-mc/fsl-mc-msi.c             | 10 +++-
> >  drivers/bus/fsl-mc/fsl-mc-private.h         |  4 +-
> >  drivers/irqchip/irq-gic-v3-its-fsl-mc-msi.c | 71
> ++++++++++++++++++++++++++++-
> >  include/linux/acpi_iort.h                   |  5 ++
> >  7 files changed, 174 insertions(+), 20 deletions(-)
> >
> > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> > index 33f7198..beb9cd5 100644
> > --- a/drivers/acpi/arm64/iort.c
> > +++ b/drivers/acpi/arm64/iort.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/kernel.h>
> >  #include <linux/list.h>
> >  #include <linux/pci.h>
> > +#include <linux/fsl/mc.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/slab.h>
> >
> > @@ -622,6 +623,29 @@ static int iort_dev_find_its_id(struct device
> > *dev, u32 req_id,  }
> >
> >  /**
> > + * iort_get_fsl_mc_device_domain() - Find MSI domain related to a
> > +device
> > + * @dev: The device.
> > + * @mc_icid: ICID for the fsl_mc device.
> > + *
> > + * Returns: the MSI domain for this device, NULL otherwise  */ struct
> > +irq_domain *iort_get_fsl_mc_device_domain(struct device *dev,
> > +                                                     u32 mc_icid) {
> > +     struct fwnode_handle *handle;
> > +     int its_id;
> > +
> > +     if (iort_dev_find_its_id(dev, mc_icid, 0, &its_id))
> > +             return NULL;
> > +
> > +     handle = iort_find_domain_token(its_id);
> > +     if (!handle)
> > +             return NULL;
> > +
> > +     return irq_find_matching_fwnode(handle, DOMAIN_BUS_FSL_MC_MSI);
> > +}
> 
> NAK
> 
> I am not willing to take platform specific code in the generic IORT layer.
> 
> ACPI on ARM64 works on platforms that comply with SBSA/SBBR guidelines:
> 
> 
> https://developer.arm.com/architectures/platform-design/server-systems
>
> Deviating from those requires butchering ACPI specifications (ie IORT) and
> related kernel code which goes totally against what ACPI is meant for on ARM64
> systems, so there is no upstream pathway for this code I am afraid.
> 
Reason of adding this platform specific function in the generic IORT layer is 
That iort_get_device_domain() only deals with PCI bus (DOMAIN_BUS_PCI_MSI).

fsl-mc objects when probed, need to find irq_domain which is associated with
the fsl-mc bus (DOMAIN_BUS_FSL_MC_MSI). It will not be possible to do that
if we do not add this function because there are no other suitable APIs exported
by IORT layer to do the job.