On 20 June 2014 14:55, Ashwin Chaugule [off-list ref] wrote:

Hello,

On 12 June 2014 13:14, Ashwin Chaugule [off-list ref] wrote:

quoted

On 12 June 2014 13:02, Arnd Bergmann [off-list ref] wrote:

quoted

On Thursday 12 June 2014 12:48:10 Ashwin Chaugule wrote:

quoted

+#ifndef CONFIG_ACPI
        if (!mbox->of_xlate)
                mbox->of_xlate = of_mbox_index_xlate;
-
+#endif
        mutex_lock(&con_mutex);
        list_add_tail(&mbox->node, &mbox_cons);
        mutex_unlock(&con_mutex);

You can't do #ifndef here, the driver must still work if
both OF and ACPI are enabled.

Ok. Here we could skip the macro altogether, since of_xlate wont be
called with ACPI anyway.

Will need to look into using/faking mbox->dev to remove the other ifndefs.

So, in order to get an mbox->dev for ACPI platforms, we'd need an
entry in the DSDT table. That seems rather pointless, since the DSDT
is reserved for devices and is supposed to be OS agnostic. Since the
mailbox controller itself is not really a "device" with a resource
descriptor, I dont see the point in adding a dummy DSDT entry for the
sake of getting this `struct device`. Also, I'm told adding new
entries to this table requires registering a unique 4 character
identifier and approval from some committees. If there are other ways
to get this structure I'd like to hear about it.

The other alternative would be to piggy back on the ACPI CPU detection
code, which looks for the ACPI0007 device node in the DSDT and use
that as the mbox controller device. This node is already registered
and is an established method to detect CPUs. But I'm not sure what
happens when CPUs are hotplugged off, we surely dont want mailbox
clients such as PCC to break.

The third alternative is to ignore the dev refcounts for ACPI as shown
in this totally untested patch:

----------------8<----------------------------------------


From 6fe6e583f0b23b08643a4a85545a9a5338b9b1a0 Mon Sep 17 00:00:00 2001
From: Ashwin Chaugule <redacted>
Date: Wed, 11 Jun 2014 16:09:35 -0400
Subject: [PATCH] Mailbox: Add support for ACPI

The current mailbox framework only supports DT based bindings.
Add another mechanism for mailbox clients to register with mailbox
controllers and request for specific mailbox channels. This enables
usage of the mailbox framework on kernels with ACPI support.

Signed-off-by: Ashwin Chaugule <redacted>
---
 drivers/mailbox/mailbox.c          | 177 ++++++++++++++++++++++++++-----------
 include/linux/mailbox_client.h     |   2 +-
 include/linux/mailbox_controller.h |   1 +
 3 files changed, 129 insertions(+), 51 deletions(-)

-------------------------8<-------------------------------

Btw I havent rebased to v7 of the mailbox patchwork yet, since I'd
like to hear feedback on the direction I'm taking with ACPI before I
rebase.

That probably messed up the formatting.. Attaching the patch.
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