linux-kernel - Re: [PATCH v2 3/6] dt-bindings: soc: Add a binding for the Broadcom VCHIQ services.

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Message-ID: <CAL_Jsq+1-9-RGfzPimYwCokEZx1vef_PX5rkp-c8s6fUchg=ag@mail.gmail.com>
Date:   Wed, 7 Mar 2018 14:00:29 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Eric Anholt <eric@...olt.net>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Phil Elwell <phil@...pberrypi.org>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stefan Wahren <stefan.wahren@...e.com>,
        bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v2 3/6] dt-bindings: soc: Add a binding for the Broadcom
 VCHIQ services.

On Wed, Mar 7, 2018 at 12:57 PM, Eric Anholt <eric@...olt.net> wrote:
> The VCHIQ communication channel can be provided by BCM283x and Capri
> SoCs, to communicate with the VPU-side OS services.
>
> Signed-off-by: Eric Anholt <eric@...olt.net>
> ---
>
> v2: dropped firmware property, added cache-line-size.
>
>  .../bindings/soc/bcm/brcm,bcm2835-vchiq.txt        | 28 ++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/bcm/brcm,bcm2835-vchiq.txt
>
> diff --git a/Documentation/devicetree/bindings/soc/bcm/brcm,bcm2835-vchiq.txt b/Documentation/devicetree/bindings/soc/bcm/brcm,bcm2835-vchiq.txt
> new file mode 100644
> index 000000000000..cdef4abc5e47
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/bcm/brcm,bcm2835-vchiq.txt
> @@ -0,0 +1,28 @@
> +Broadcom VCHIQ firmware services
> +
> +Required properties:
> +
> +- compatible:  Should be "brcm,bcm2835-vchiq"
> +- reg:         Physical base address and length of the doorbell register pair
> +- interrupts:  The interrupt number
> +                 See bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt
> +
> +Optional properties:
> +
> +- cache-line-size:
> +               Size of L2 cache lines.  The VPU firmware detects
> +                 this property and overrides it with the actual L2
> +                 cache line size it's using when loading the
> +                 device-tree.  Determines the required alignment of
> +                 offsets/sizes of VCHIQ pagelists.  If missing, the
> +                 firmware assumes an older kernel using 32-byte
> +                 alignment.

How is this a VCHIQ property? This is a standard property for cache
nodes, but this is not a cache node.

Is it really a problem to just use a fixed maximum alignment? That
seems to be good enough for all the rest of the kernel.

> +
> +Example:
> +
> +vchiq@...0b840 {

mailbox@...

> +       compatible = "brcm,bcm2835-vchiq";
> +       reg = <0x7e00b840 0xf>;
> +       interrupts = <0 2>;
> +       cache-line-size: <32>;
> +};
> --
> 2.16.2
>