linux-kernel - Re: [PATCH] mailbox: arm_mhu: add support for mhuv2

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Message-ID: <CABb+yY00AJ3ZBAU3R-=eaLJfBooY23JAiPaYxi=8MdCczKmZHw@mail.gmail.com>
Date:   Wed, 2 May 2018 17:34:17 +0530
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Samarth Parikh <samarth.parikh@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sudipto.Paul@....com, Arvind.Chauhan@....com, samarthp@...il.com,
        Deepak.Pandey@....com, Sudeep Holla <Sudeep.Holla@....com>
Subject: Re: [PATCH] mailbox: arm_mhu: add support for mhuv2

On Wed, May 2, 2018 at 12:44 PM, Samarth Parikh <samarth.parikh@....com> wrote:
> Hi Jassi,
>
> I am resending the patch for review, in case you have missed my previous
> patch. Can you please go through it and let me know your thoughts on
> the same?
>
You don't want this to go into git log :)
If your patch isn't looked into for more than 2weeks (or longer if
merge window is not near), please just ping as a reply to original
submission.
Anyways....

> ARM has launched a next version of MHU i.e. MHUv2 with its latest
> subsystems. The main change is that the MHUv2 is now a distributed IP
> with different peripheral views (registers) for the sender and receiver.
>
> Another main difference is that MHUv1 duplex channels are now split into
> simplex/half duplex in MHUv2. MHUv2 has a configurable number of
> communication channels. There is a capability register (MSG_NO_CAP) to
> find out how many channels are available in a system.
>
> The register offsets have also changed for STAT, SET & CLEAR registers
> from 0x0, 0x8 & 0x10 in MHUv1 to 0x0, 0xC & 0x8 in MHUv2 respectively.
>
> 0x0    0x4  0x8  0xC             0x1F
> ------------------------....-----
> | STAT |    |    | SET |    |   |
> ------------------------....-----
>       Transmit Channel
>
> 0x0    0x4  0x8   0xC            0x1F
> ------------------------....-----
> | STAT |    | CLR |    |    |   |
> ------------------------....-----
>         Receive Channel
>
> The MHU controller can request the receiver to wake-up and once the
> request is removed, the receiver may go back to sleep, but the MHU
> itself does not actively puts a receiver to sleep.
>
> So, in order to wake-up the receiver when the sender wants to send data,
> the sender has to set ACCESS_REQUEST register first in order to wake-up
> receiver, state of which can be detected using ACCESS_READY register.
> ACCESS_REQUEST has an offset of 0xF88 & ACCESS_READY has an offset
> of 0xF8C and are accessible only on any sender channel.
>
> This patch adds necessary changes required to support the older
> version of MHU & the latest MHUv2 controller. This patch also need an
> update in DT binding for ARM MHU as we need a second register base
> (tx base) which would be used as the send channel base.
>
> Signed-off-by: Samarth Parikh <samarth.parikh@....com>
> ---
>  drivers/mailbox/arm_mhu.c | 163 ++++++++++++++++++++++++++++++++++++++++++----
>  1 file changed, 151 insertions(+), 12 deletions(-)
>
The original driver is 195 loc, this patch makes it almost double the size.
Also there have been controllers (resembling closer to MHU than this
one) with separate drivers. So I think we should simply create another
arm_mhu_v2.c ?

Cheers!