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

[Nikunj Kela]

On 7/18/2023 11:17 AM, Krzysztof Kozlowski wrote:
> 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?
I mimic the same behavior as in smc.c. At the moment, we don't have a 
use case for atomicity but was trying to keep the same skeleton in case 
we need to add the atomic support in future. But you are right, I don't 
need wrapper at the moment.
> > +{
> > +	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.
Will remove the wrappers.
> > +}
> > +
> > +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.
Wouldn't the devm_* API take care of that implicitly? It is same in 
smc.c as well.
> > +		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.
This is copied as is from existing smc.c
> Best regards,
> Krzysztof