-----Original Message-----
From: Ard Biesheuvel <redacted>
Sent: Friday, January 31, 2020 5:32 PM
To: Marc Zyngier <maz@kernel.org>
Cc: Makarand Pawagi <redacted>; Calvin Johnson
[off-list ref]; stuyoder@gmail.com; nleeder@codeaurora.org;
Ioana Ciornei [off-list ref]; Cristi Sovaiala
[off-list ref]; Hanjun Guo [off-list ref]; Will
Deacon [off-list ref]; Lorenzo Pieralisi [off-list ref];
Pankaj Bansal [off-list ref]; jon@solid-run.com; Russell King
[off-list ref]; ACPI Devel Maling List [off-list ref];
Len Brown [off-list ref]; Jason Cooper [off-list ref]; Andy
Wang [off-list ref]; Varun Sethi [off-list ref]; Thomas
Gleixner [off-list ref]; linux-arm-kernel <linux-arm-
kernel@lists.infradead.org>; Laurentiu Tudor [off-list ref]; Paul
Yang [off-list ref]; [off-list ref]
[off-list ref]; Rafael J. Wysocki [off-list ref]; Linux Kernel
Mailing List [off-list ref]; Shameerali Kolothum Thodi
[off-list ref]; Sudeep Holla
[off-list ref]; Robin Murphy [off-list ref]
Subject: Re: [EXT] Re: [PATCH] bus: fsl-mc: Add ACPI support for fsl-mc

On Fri, 31 Jan 2020 at 12:06, Marc Zyngier [off-list ref] wrote:

quoted

On 2020-01-31 10:35, Makarand Pawagi wrote:

quoted

quoted

-----Original Message-----
From: Lorenzo Pieralisi <redacted>
Sent: Tuesday, January 28, 2020 4:39 PM
To: Makarand Pawagi <redacted>
Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
linux-arm- kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
linux@armlinux.org.uk; jon@solid-run.com; Cristi Sovaiala
[off-list ref]; Laurentiu Tudor
[off-list ref]; Ioana Ciornei [off-list ref];
Varun Sethi [off-list ref]; Calvin Johnson
[off-list ref]; Pankaj Bansal [off-list ref];
guohanjun@huawei.com; sudeep.holla@arm.com; rjw@rjwysocki.net;
lenb@kernel.org; stuyoder@gmail.com; tglx@linutronix.de;
jason@lakedaemon.net; maz@kernel.org;
shameerali.kolothum.thodi@huawei.com; will@kernel.org;
robin.murphy@arm.com; nleeder@codeaurora.org
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:

quoted

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 <redacted>
---
 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

++++++++++++++++++++++++++++-

quoted

 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://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fd
eveloper.arm.com%2Farchitectures%2Fplatform-design%2Fserver-systems

&data=02%7C01%7Cpankaj.bansal%40nxp.com%7Cdb56d889d85646277ee
30

quoted

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8d7a64562fa%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C6371606
892

quoted

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50769265&sdata=C7nCty8%2BVeuq6VhcEUXCwiAinN01rCfe12NRVnXJCIY%
3D

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&reserved=0

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.

I think we all understood the patch. What both Lorenzo and myself are
saying is that we do not want non-PCI support in IORT.

IORT supports platform devices (aka named components) as well, and
there is some support for platform MSIs in the GIC layer.

So it may be possible to hide your exotic bus from the OS entirely,
and make the firmware instantiate a DSDT with device objects and
associated IORT nodes that describe whatever lives on that bus as
named components.

That way, you will not have to change the OS at all, so your hardware
will not only be supported in linux v5.7+, it will also be supported
by OSes that commercial distro vendors are shipping today. *That* is
the whole point of using ACPI.

If you are going to bother and modify the OS, you lose this advantage,
and ACPI gives you no benefit over DT at all.

I am replying to old message in this conversation, because the discussion got sidetracked from IORT
table to SFP/QSFP/devlink stuff from this point onwards, which is not related to IORT.
I will only focus on representing the MC device in IORT and using the same in linux.
As Ard said:
"IORT supports platform devices (aka named components) as well, and
there is some support for platform MSIs in the GIC layer."

We can represent MC bus as named component in IORT table and use platform MSIs.
The only caveat is that with current implementation of platform MSIs, the Input id of a device is not considered.
https://elixir.bootlin.com/linux/latest/source/drivers/irqchip/irq-gic-v3-its-platform-msi.c#L50
https://elixir.bootlin.com/linux/latest/source/drivers/acpi/arm64/iort.c#L464

While, IORT spec doesn't specify any such limitation.

we can easily update iort.c to remove this limitation.
But, I am not sure how the input id would be passed from platform MSI GIC layer to IORT.
Most obviously, the input id should be supplied by dev itself.

Any thoughts?

If we go by this path, I think we can remove special handling for fsl-mc for of* cases altogether.
https://elixir.bootlin.com/linux/latest/source/drivers/irqchip/irq-gic-v3-its-fsl-mc-msi.c

Regards,
Pankaj Bansal
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