linux-kernel - Re: [PATCH v5 2/2] mailbox: introduce ARM SMC based mailbox

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Date:   Wed, 28 Aug 2019 15:02:17 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Peng Fan <peng.fan@....com>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
        "andre.przywara@....com" <andre.przywara@....com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v5 2/2] mailbox: introduce ARM SMC based mailbox

On Wed, Aug 28, 2019 at 03:03:02AM +0000, Peng Fan wrote:
> From: Peng Fan <peng.fan@....com>
>
> This mailbox driver implements a mailbox which signals transmitted data
> via an ARM smc (secure monitor call) instruction. The mailbox receiver
> is implemented in firmware and can synchronously return data when it
> returns execution to the non-secure world again.
> An asynchronous receive path is not implemented.
> This allows the usage of a mailbox to trigger firmware actions on SoCs
> which either don't have a separate management processor or on which such
> a core is not available. A user of this mailbox could be the SCP
> interface.
>
> Modified from Andre Przywara's v2 patch
> https://lore.kernel.org/patchwork/patch/812999/
>
> Cc: Andre Przywara <andre.przywara@....com>
> Signed-off-by: Peng Fan <peng.fan@....com>
> ---
>  drivers/mailbox/Kconfig           |   7 ++
>  drivers/mailbox/Makefile          |   2 +
>  drivers/mailbox/arm-smc-mailbox.c | 215 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 224 insertions(+)
>  create mode 100644 drivers/mailbox/arm-smc-mailbox.c
>

[...]

> +static int arm_smc_mbox_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct mbox_controller *mbox;
> +	struct arm_smc_chan_data *chan_data;
> +	const char *method;
> +	bool mem_trans = false;
> +	int ret, i;
> +	u32 val;
> +
> +	if (!of_property_read_u32(dev->of_node, "arm,num-chans", &val)) {
> +		if (!val) {
> +			dev_err(dev, "invalid arm,num-chans value %u\n", val);
> +			return -EINVAL;
> +		}
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	if (!of_property_read_string(dev->of_node, "transports", &method)) {
> +		if (!strcmp("mem", method)) {
> +			mem_trans = true;
> +		} else if (!strcmp("reg", method)) {
> +			mem_trans = false;
> +		} else {
> +			dev_warn(dev, "invalid \"transports\" property: %s\n",
> +				 method);
> +
> +			return -EINVAL;
> +		}
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	if (!of_property_read_string(dev->of_node, "method", &method)) {
> +		if (!strcmp("hvc", method)) {
> +			invoke_smc_mbox_fn = __invoke_fn_hvc;
> +		} else if (!strcmp("smc", method)) {
> +			invoke_smc_mbox_fn = __invoke_fn_smc;
> +		} else {
> +			dev_warn(dev, "invalid \"method\" property: %s\n",
> +				 method);
> +
> +			return -EINVAL;
> +		}
> +	} else {
> +		return -EINVAL;
> +	}
> +
> +	mbox = devm_kzalloc(dev, sizeof(*mbox), GFP_KERNEL);
> +	if (!mbox)
> +		return -ENOMEM;
> +
> +	mbox->num_chans = val;
> +	mbox->chans = devm_kcalloc(dev, mbox->num_chans, sizeof(*mbox->chans),
> +				   GFP_KERNEL);
> +	if (!mbox->chans)
> +		return -ENOMEM;
> +
> +	chan_data = devm_kcalloc(dev, mbox->num_chans, sizeof(*chan_data),
> +				 GFP_KERNEL);
> +	if (!chan_data)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < mbox->num_chans; i++) {
> +		u32 function_id;
> +
> +		ret = of_property_read_u32_index(dev->of_node,
> +						 "arm,func-ids", i,
> +						 &function_id);

I missed it in binding but I thought we agreed to make this "arm,func-ids"
a required property and not optional ?

--
Regards,
Sudeep