linux-kernel - Re: [PATCH v6 2/6] mailbox: sun6i-msgbox: Add a new mailbox driver

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Date:   Mon, 13 Jan 2020 10:15:58 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Samuel Holland <samuel@...lland.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jassi Brar <jassisinghbrar@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ondrej Jirman <megous@...ous.com>,
        Vasily Khoruzhick <anarsoul@...il.com>
Cc:     devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v6 2/6] mailbox: sun6i-msgbox: Add a new mailbox driver

On Sun, 2020-01-12 at 23:18 -0600, Samuel Holland wrote:
> Allwinner sun6i, sun8i, sun9i, and sun50i SoCs contain a hardware
> message box used for communication between the ARM CPUs and the ARISC
> management coprocessor. This mailbox contains 8 unidirectional
> 4-message FIFOs.
> 
> Add a driver for it, so it can be used for SCPI or other communication
> protocols.
> 
> Signed-off-by: Samuel Holland <samuel@...lland.org>
> ---
>  drivers/mailbox/Kconfig        |   9 +
>  drivers/mailbox/Makefile       |   2 +
>  drivers/mailbox/sun6i-msgbox.c | 332 +++++++++++++++++++++++++++++++++
>  3 files changed, 343 insertions(+)
>  create mode 100644 drivers/mailbox/sun6i-msgbox.c
> 
[...]
> diff --git a/drivers/mailbox/sun6i-msgbox.c b/drivers/mailbox/sun6i-msgbox.c
> new file mode 100644
> index 000000000000..15d6fd522dc5
> --- /dev/null
> +++ b/drivers/mailbox/sun6i-msgbox.c
> @@ -0,0 +1,332 @@
[...]
> +	reset = devm_reset_control_get_exclusive(dev, NULL);
> +	if (IS_ERR(reset)) {
> +		ret = PTR_ERR(reset);
> +		dev_err(dev, "Failed to get reset control: %d\n", ret);
> +		goto err_disable_unprepare;
> +	}
> +
> +	/*
> +	 * NOTE: We rely on platform firmware to preconfigure the channel
> +	 * directions, and we share this hardware block with other firmware
> +	 * that runs concurrently with Linux (e.g. a trusted monitor).
> +	 *
> +	 * Therefore, we do *not* assert the reset line if probing fails or
> +	 * when removing the device.
> +	 */
> +	ret = reset_control_deassert(reset);
> +	if (ret) {
> +		dev_err(dev, "Failed to deassert reset: %d\n", ret);
> +		goto err_disable_unprepare;
> +	}

Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

regards
Philipp