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

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Message-ID: <FDE42FCD-8E61-4EE5-8893-6A9E7E7D64AC@arm.com>
Date:   Mon, 14 May 2018 08:07:39 +0000
From:   Samarth Parikh <Samarth.Parikh@....com>
To:     Jassi Brar <jassisinghbrar@...il.com>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sudipto Paul <Sudipto.Paul@....com>,
        Arvind Chauhan <Arvind.Chauhan@....com>,
        "samarthp@...il.com" <samarthp@...il.com>,
        Deepak Pandey <Deepak.Pandey@....com>,
        Sudeep Holla <Sudeep.Holla@....com>
Subject: Re: [PATCH] mailbox: arm_mhu: add support for mhuv2

Hi Jassi,

As suggested by you, I have moved the MHUv2 related changes to a new file arm_mhu_v2.c. I have sent an updated patch, can you please review it?

Regards,
Samarth

On 02/05/18, 5:34 PM, "Jassi Brar" <jassisinghbrar@...il.com> wrote:

    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!


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