linux-kernel - Re: [PATCH 2/2] firmware: arm_scmi: Add qcom hvc/shmem transport

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Message-ID: <d9d5ffd5-6f85-f091-5d69-12cdd8d04c99@linaro.org>
Date:   Tue, 18 Jul 2023 20:17:20 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Nikunj Kela <quic_nkela@...cinc.com>, sudeep.holla@....com
Cc:     cristian.marussi@....com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        agross@...nel.org, andersson@...nel.org, konrad.dybcio@...aro.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/2] firmware: arm_scmi: Add qcom hvc/shmem transport

On 18/07/2023 18:08, Nikunj Kela wrote:
> Add a new transport channel to the SCMI firmware interface driver for
> SCMI message exchange on Qualcomm virtual platforms.
> 
> The hypervisor associates an object-id also known as capability-id
> with each hvc doorbell object. The capability-id is used to identify the
> doorbell from the VM's capability namespace, similar to a file-descriptor.
> 

...

> +
> +static bool qcom_hvc_chan_available(struct device_node *of_node, int idx)
> +{
> +	struct device_node *np = of_parse_phandle(of_node, "shmem", 0);
> +
> +	if (!np)
> +		return false;
> +
> +	of_node_put(np);
> +	return true;
> +}
> +
> +static inline void qcom_hvc_channel_lock_init(struct scmi_qcom_hvc *scmi_info)
> +{
> +	mutex_init(&scmi_info->shmem_lock);
> +}
> +
> +static inline void
> +qcom_hvc_channel_lock_acquire(struct scmi_qcom_hvc *scmi_info,
> +			      struct scmi_xfer *xfer __maybe_unused)

Why do you pass unused arguments?

> +{
> +	mutex_lock(&scmi_info->shmem_lock);

Why do you need these wrappers? Why not using mutexes directly?
If they are needed, then add lock __acquires annotation.


> +}
> +
> +static inline void qcom_hvc_channel_lock_release(struct scmi_qcom_hvc
> +						 *scmi_info)

Same comments.

> +{
> +	mutex_unlock(&scmi_info->shmem_lock);
> +}
> +
> +static int qcom_hvc_chan_setup(struct scmi_chan_info *cinfo,
> +			       struct device *dev, bool tx)
> +{
> +	struct device *cdev = cinfo->dev;
> +	struct scmi_qcom_hvc *scmi_info;
> +	resource_size_t size;
> +	struct resource res;
> +	struct device_node *np;
> +	unsigned long cap_id;
> +	u32 func_id;
> +	int ret, irq;
> +
> +	if (!tx)
> +		return -ENODEV;
> +
> +	scmi_info = devm_kzalloc(dev, sizeof(*scmi_info), GFP_KERNEL);
> +	if (!scmi_info)
> +		return -ENOMEM;
> +
> +	np = of_parse_phandle(cdev->of_node, "shmem", 0);
> +	if (!of_device_is_compatible(np, "arm,scmi-shmem"))

You leak here reference.

> +		return -ENXIO;
> +
> +	ret = of_address_to_resource(np, 0, &res);
> +	of_node_put(np);
> +	if (ret) {
> +		dev_err(cdev, "failed to get SCMI Tx shared memory\n");
> +		return ret;
> +	}
> +
> +	size = resource_size(&res);
> +
> +	/* let's map 2 additional ulong since
> +	 * func-id & capability-id are kept after shmem.
> +	 *     +-------+
> +	 *     |       |
> +	 *     | shmem |
> +	 *     |       |
> +	 *     |       |
> +	 *     +-------+ <-- size
> +	 *     | funcId|
> +	 *     +-------+ <-- size + sizeof(ulong)
> +	 *     | capId |
> +	 *     +-------+ <-- size + 2*sizeof(ulong)
> +	 */
> +
> +	scmi_info->shmem = devm_ioremap(dev, res.start,
> +					size + 2 * sizeof(unsigned long));
> +	if (!scmi_info->shmem) {
> +		dev_err(dev, "failed to ioremap SCMI Tx shared memory\n");
> +		return -EADDRNOTAVAIL;
> +	}
> +
> +	func_id = readl((void *)(scmi_info->shmem) + size);
> +
> +#ifdef CONFIG_ARM64
> +	cap_id = readq((void *)(scmi_info->shmem) + size +
> +		       sizeof(unsigned long));
> +#else
> +	cap_id = readl((void *)(scmi_info->shmem) + size +
> +		       sizeof(unsigned long));
> +#endif
> +
> +	/*
> +	 * If there is an interrupt named "a2p", then the service and
> +	 * completion of a message is signaled by an interrupt rather than by
> +	 * the return of the hvc call.
> +	 */
> +	irq = of_irq_get_byname(cdev->of_node, "a2p");
> +	if (irq > 0) {
> +		ret = devm_request_irq(dev, irq, qcom_hvc_msg_done_isr,
> +				       IRQF_NO_SUSPEND,
> +				       dev_name(dev), scmi_info);
> +		if (ret) {
> +			dev_err(dev, "failed to setup SCMI completion irq\n");

return dev_err_probe, unless this is not called in probe... but then
using devm-interface raises questions.

Best regards,
Krzysztof