Message-ID: <20200430092358.GI948789@vkoul-mobl.Dlink>
Date:   Thu, 30 Apr 2020 14:53:58 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org, robh+dt@...nel.org,
        jassisinghbrar@...il.com, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Venkata Narendra Kumar Gutta <vnkgutta@...eaurora.org>,
        Raghavendra Rao Ananta <rananta@...eaurora.org>
Subject: Re: [PATCH 2/2] soc: qcom: ipcc: Add support for IPCC controller

On 30-04-20, 14:32, Manivannan Sadhasivam wrote:
> Hi,
> 
> On Thu, Apr 30, 2020 at 12:54:48PM +0530, Vinod Koul wrote:
> > On 30-04-20, 12:00, Manivannan Sadhasivam wrote:
> > 
> > > +#define IPCC_SIGNAL_ID_MASK		GENMASK(15, 0)
> > > +#define IPCC_CLIENT_ID_MASK		GENMASK(31, 16)
> > > +#define IPCC_CLIENT_ID_SHIFT		16
> > > +
> > > +#define IPCC_NO_PENDING_IRQ		0xffffffff
> > 
> > Why not GENMASK(31, 0)
> > 
> 
> Hmm, I usually use GENMASK for mask defines. But yeah it can be used here.

Well the idea behind genmask was to avoid coding mistakes which sounds
apt here as well :)

> 
> > > +static struct qcom_ipcc_proto_data *ipcc_proto_data;
> > 
> > why do we need a global which is used only once.
> > 
> 
> Ah, that's a left over. Will remove it.
> 
> > > +static void qcom_ipcc_mask_irq(struct irq_data *irqd)
> > > +{
> > > +	struct qcom_ipcc_proto_data *proto_data;
> > > +	irq_hw_number_t hwirq = irqd_to_hwirq(irqd);
> > > +	u16 sender_client_id = qcom_ipcc_get_client_id(hwirq);
> > > +	u16 sender_signal_id = qcom_ipcc_get_signal_id(hwirq);
> > 
> > last three are used for debug log, fn can be much simpler if we get rid
> > of noise.. Do we really need this to be production :)
> > 
> 
> This is for debugging the production systems, that's why dev_dbg. So I don't
> consider it as a noise :)

This in an irq chip, the debug code is much more than actual function!
Anyone who wants to debug can add these lines :)

> > > +	proto_data = irq_data_get_irq_chip_data(irqd);
> > > +
> > > +	dev_dbg(proto_data->dev,
> > > +		"Disabling interrupts for: client_id: %u; signal_id: %u\n",
> > > +		sender_client_id, sender_signal_id);
> > > +
> > > +	writel(hwirq, proto_data->base + IPCC_REG_RECV_SIGNAL_DISABLE);
> > > +}
> > > +
> > > +static void qcom_ipcc_unmask_irq(struct irq_data *irqd)
> > > +{
> > > +	struct qcom_ipcc_proto_data *proto_data;
> > > +	irq_hw_number_t hwirq = irqd_to_hwirq(irqd);
> > > +	u16 sender_client_id = qcom_ipcc_get_client_id(hwirq);
> > > +	u16 sender_signal_id = qcom_ipcc_get_signal_id(hwirq);
> > 
> > here as well
> > 
> > > +static int qcom_ipcc_domain_xlate(struct irq_domain *d,
> > > +				  struct device_node *node, const u32 *intspec,
> > > +				  unsigned int intsize,
> > > +				  unsigned long *out_hwirq,
> > > +				  unsigned int *out_type)
> > 
> > pls align these to match open parenthesis
> > 
> 
> It is aligned. Perhaps diff is showing it as mangled due to ignoring
> whitespaces?

Not sure, even checkpatch seems to think so

> 
> > > +static int qcom_ipcc_setup_mbox(struct qcom_ipcc_proto_data *proto_data,
> > > +				struct device_node *controller_dn)
> > > +{
> > > +	struct mbox_controller *mbox;
> > > +	struct device_node *client_dn;
> > > +	struct device *dev = proto_data->dev;
> > > +	struct of_phandle_args curr_ph;
> > > +	int i, j, ret;
> > > +	int num_chans = 0;
> > > +
> > > +	/*
> > > +	 * Find out the number of clients interested in this mailbox
> > > +	 * and create channels accordingly.
> > > +	 */
> > > +	for_each_node_with_property(client_dn, "mboxes") {
> > > +		if (!of_device_is_available(client_dn))
> > > +			continue;
> > > +		i = of_count_phandle_with_args(client_dn,
> > > +					       "mboxes", "#mbox-cells");
> > > +		for (j = 0; j < i; j++) {
> > > +			ret = of_parse_phandle_with_args(client_dn, "mboxes",
> > > +							 "#mbox-cells", j,
> > > +							 &curr_ph);
> > 
> > this sounds like something DT should do, not drivers :)
> > 
> 
> Right. This is design discussion I'd like to have. Currently the driver checks
> the DT and allocates the total number of mbox channels. But I think the more
> cleaner way would be to have this driver allocating fixed number of channels
> statically and let the clients use it.

Sorry my point was about code of checking mboxes and #mbox-cells, these
seems generic enough and could be moved into of core code :)

But I think making fixed number of channels should not be done if DT can
provide this information.

> Maybe Raghavendra/Venkat can comment here?
> 
> > > +static int qcom_ipcc_probe(struct platform_device *pdev)
> > > +{
> > > +	struct qcom_ipcc_proto_data *proto_data;
> > > +	int ret;
> > > +
> > > +	proto_data = devm_kzalloc(&pdev->dev, sizeof(*proto_data), GFP_KERNEL);
> > > +	if (!proto_data)
> > > +		return -ENOMEM;
> > > +
> > > +	ipcc_proto_data = proto_data;
> > > +	proto_data->dev = &pdev->dev;
> > > +
> > > +	proto_data->base = devm_platform_ioremap_resource(pdev, 0);
> > > +	if (IS_ERR(proto_data->base)) {
> > > +		dev_err(&pdev->dev, "Failed to ioremap the ipcc base addr\n");
> > > +		return PTR_ERR(proto_data->base);
> > > +	}
> > > +
> > > +	proto_data->irq = platform_get_irq(pdev, 0);
> > > +	if (proto_data->irq < 0) {
> > > +		dev_err(&pdev->dev, "Failed to get the IRQ\n");
> > > +		return proto_data->irq;
> > > +	}
> > > +
> > > +	/* Perform a SW reset on this client's protocol state */
> > > +	writel(0x1, proto_data->base + IPCC_REG_CLIENT_CLEAR);
> > > +
> > > +	proto_data->irq_domain = irq_domain_add_tree(pdev->dev.of_node,
> > > +						     &qcom_ipcc_irq_ops,
> > > +						     proto_data);
> > > +	if (!proto_data->irq_domain) {
> > > +		dev_err(&pdev->dev, "Failed to add irq_domain\n");
> > > +		return -ENOMEM;
> > > +	}
> > > +
> > > +	ret = qcom_ipcc_setup_mbox(proto_data, pdev->dev.of_node);
> > > +	if (ret) {
> > > +		dev_err(&pdev->dev, "Failed to create mailbox\n");
> > > +		goto err_mbox;
> > > +	}
> > > +
> > > +	ret = devm_request_irq(&pdev->dev, proto_data->irq, qcom_ipcc_irq_fn,
> > > +			       IRQF_TRIGGER_HIGH, "ipcc", proto_data);
> > > +	if (ret < 0) {
> > > +		dev_err(&pdev->dev, "Failed to register the irq: %d\n", ret);
> > 
> > Should the qcom_ipcc_setup_mbox() not be unroller here?
> 
> qcom_ipcc_setup_mbox() uses devm_ API for registering mbox controller. So what
> is the issue?

Ah missed the devm parts, i think no unroll required here

> > > +		goto err_mbox;
> > > +	}
> > > +
> > > +	enable_irq_wake(proto_data->irq);
> > > +	platform_set_drvdata(pdev, proto_data);
> > > +
> > > +	return 0;
> > > +
> > > +err_mbox:
> > > +	irq_domain_remove(proto_data->irq_domain);
> > > +
> > > +	return ret;
> > > +}
> > > +
> > > +static int qcom_ipcc_remove(struct platform_device *pdev)
> > > +{
> > > +	struct qcom_ipcc_proto_data *proto_data = platform_get_drvdata(pdev);
> > > +
> > > +	disable_irq_wake(proto_data->irq);
> > > +	irq_domain_remove(proto_data->irq_domain);
> > 
> > So you are calling this when your isr is active, we have possibility of
> > race here. This function come with a warning:
> > "The caller must ensure that all mappings within the domain have been disposed"
> 
> I thought it is not required since most of the interrupt controller drivers
> don't do it. But checked with Marc Zyngier and he suggested to dispose the
> mapping as that's the good practice. The usual pattern is an interrupt
> controller is not built as a module and the assumption is it lives forever.
> 
> But one issue here is, currently we don't know the allocated irqs (in specific
> hw irq numbers) as we don't create the mapping. It gets created when a client
> calls platform_get_irq(). In the irq handler, we just read the current hw irq
> number from a register. So, if we want to dispose the mapping then we need to
> track the allocated irqs. Else we need to create the mapping for all possible
> clients in this driver itself. I'm not sure which one is preferred.
> 
> Maybe Bjorn/qcom folks can comment what is preferred here?

Maybe this should also be lives forever cases then! :)

-- 
~Vinod

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