Subject: Re: [patch 1/1] pmi: initial version

From: Christian Krafft <[email-masked]>
Date: Mon, 12 Feb 2007 10:12:22 +0100

Hi Nathan,

thanks for your comments.
Will send an updated version.

On Fri, 9 Feb 2007 16:29:56 -0600
Nathan Lynch <[email-masked]> wrote:

> Hi Christian-
> 
> Some minor comments.
> 
> Christian Krafft wrote:
> > This patch adds driver code for the PMI device found in future IBM products.
> > PMI stands for "Platform Management Interrupt" and is a way to communicate
> > with the BMC. It provides bidirectional communication with a low latency.
> > 
> > Signed-off-by: Christian Krafft <[email-masked]>
> > 
> > Index: linux/arch/powerpc/Kconfig
> > ===================================================================
> > --- linux.orig/arch/powerpc/Kconfig
> > +++ linux/arch/powerpc/Kconfig
> > @@ -524,6 +524,7 @@ config PPC_IBM_CELL_BLADE
> >  	select MMIO_NVRAM
> >  	select PPC_UDBG_16550
> >  	select UDBG_RTAS_CONSOLE
> > +#	select PPC_PMI
> 
> Did you mean for this to be commented out?

no, good point ;-)

> 
> <snip>
> 
> > +static void __iomem *of_iomap(struct device_node *np)
> > +{
> > +	struct resource res;
> > +
> > +	if (of_address_to_resource(np, 0, &res))
> > +		return NULL;
> > +
> > +	pr_debug("Resource start: 0x%lx\n", res.start);
> > +        pr_debug("Resource end: 0x%lx\n", res.end);
> 
> You need a tab instead of spaces.

copy and past bug,

> 
> 
> > +
> > +	return ioremap(res.start, 1 + res.end - res.start);
> > +}
> > +
> > +static int pmi_irq_handler(int irq, void *dev_id)
> > +{
> > +	struct pmi_data *data;
> > +	int type;
> > +	struct pmi_handler *handler;
> > +
> > +	data = dev_id;
> > +
> > +	BUG_ON(!data);
> 
> Not necessary, you'll oops in two lines anyway if data is NULL.

ok,

> 
> 
> > +
> > +	pr_debug("pmi: got a PMI message\n");
> > +
> > +	spin_lock(&data->pmi_spinlock);
> > +	type = ioread8(data->pmi_reg + PMI_READ_TYPE);
> > +	spin_unlock(&data->pmi_spinlock);
> > +
> > +	pr_debug("pmi: message type is %d\n", type);
> > +
> > +	if (type & PMI_ACK) {
> > +		BUG_ON(!data->msg);
> > +		BUG_ON(!data->completion);
> > +		pr_debug("pmi: got an ACK\n");
> > +		data->msg->type = type;
> > +		data->msg->data0 = ioread8(data->pmi_reg + PMI_READ_DATA0);
> > +		data->msg->data1 = ioread8(data->pmi_reg + PMI_READ_DATA1);
> > +		data->msg->data2 = ioread8(data->pmi_reg + PMI_READ_DATA2);
> 
> Should these accesses to data->pmi_reg be performed while holding
> data->pmi_spinlock as well?

yep, good catch.

> 
> 
> > +		complete(data->completion);
> > +		return IRQ_HANDLED;
> > +	}
> > +
> > +	spin_lock(&data->handler_spinlock);
> > +	list_for_each_entry(handler, &data->handler, node) {
> > +		pr_debug("pmi: notifying handlers\n");
> > +		if (handler->type == type) {
> > +			pr_debug("pmi: notify handler %p\n", handler);
> > +			handler->handle_pmi_message(data->dev, data->msg);
> > +		}
> > +	}
> > +	spin_unlock(&data->handler_spinlock);
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> > +
> > +static struct of_device_id pmi_match[] = {
> > +	{ .type = "ibm,pmi", .name = "pmi" },
> > +	{},
> > +};
> > +
> > +MODULE_DEVICE_TABLE(of, pmi_match);
> > +
> > +static int pmi_of_probe(struct of_device *dev,
> > +			const struct of_device_id *match)
> > +{
> > +	DEFINE_SPINLOCK(handler_spinlock);
> > +	DEFINE_SPINLOCK(pmi_spinlock);
> > +
> > +	struct device_node *np = dev->node;
> > +	struct pmi_data *data;
> > +	int rc;
> > +
> > +	data = kzalloc(sizeof(struct pmi_data), GFP_KERNEL);
> > +	if (!data) {
> > +		printk(KERN_ERR "pmi: could not allocate memory.\n");
> > +		return -EFAULT;
> 
> -ENOMEM is the appropriate error code here.

will be updated.

> 
> 
> > +	}
> > +
> > +	data->pmi_reg = of_iomap(np);
> > +
> > +	if (!data->pmi_reg) {
> > +		printk(KERN_ERR "pmi: invalid register address.\n");
> > +		kfree(data);
> > +		return -EFAULT;
> > +	}
> > +
> > +	INIT_LIST_HEAD(&data->handler);
> > +
> > +	data->irq = irq_of_parse_and_map(np, 0);
> > +	if (data->irq == NO_IRQ) {
> > +		printk(KERN_ERR "pmi: invalid interrupt.\n");
> > +		iounmap(data->pmi_reg);
> > +		kfree(data);
> > +		return -EFAULT;
> > +	}
> > +
> > +	data->handler_spinlock = handler_spinlock;
> > +	data->pmi_spinlock = pmi_spinlock;
> > +
> > +	rc = request_irq(data->irq, pmi_irq_handler,
> > +			IRQF_SHARED, "pmi", data);
> > +	if (rc) {
> > +		printk(KERN_ERR "pmi: can't request IRQ %d: returned %d\n",
> > +			data->irq, rc);
> > +		iounmap(data->pmi_reg);
> > +		kfree(data);
> 
> Consider using goto to reduce duplication of the iounmap, kfree sequence.
> 
> > +		return -EFAULT;
> 
> Just return rc; request_irq returns standard error codes.

ok,

> 
> <snip>
> 
> > +void pmi_send_message(struct of_device *device, struct pmi_message *msg)
> > +{
> > +	struct pmi_data *data;
> > +	unsigned long flags;
> > +	DECLARE_COMPLETION_ONSTACK(completion);
> > +
> > +	BUG_ON(!device || !msg);
> 
> This BUG_ON is also unnecessary, and could actually make debugging
> more difficult since it wouldn't be immediately apparent which
> condition triggered it.

right,

> 
> > +
> > +	data = device->dev.driver_data;
> > +	pr_debug("pmi_send_message: data is %p\n", data);
> > +
> > +	mutex_lock(&data->msg_mutex);
> > +
> > +	data->msg = msg;
> > +
> > +	pr_debug("pmi_send_message: msg is %p\n", msg);
> > +
> > +	data->completion = &completion;
> > +
> > +	spin_lock_irqsave(&data->pmi_spinlock, flags);
> > +	iowrite8(msg->data0, data->pmi_reg + PMI_WRITE_DATA0);
> > +	iowrite8(msg->data1, data->pmi_reg + PMI_WRITE_DATA1);
> > +	iowrite8(msg->data2, data->pmi_reg + PMI_WRITE_DATA2);
> > +	iowrite8(msg->type, data->pmi_reg + PMI_WRITE_TYPE);
> > +	spin_unlock_irqrestore(&data->pmi_spinlock, flags);
> > +
> > +	pr_debug(KERN_INFO "pmi_send_message: wait for completion %p\n", data->completion);
> > +
> > +	wait_for_completion_interruptible_timeout(data->completion, PMI_TIMEOUT);
> > +
> > +	data->msg = NULL;
> > +	data->completion = NULL;
> > +
> > +	mutex_unlock(&data->msg_mutex);
> > +}
> > +EXPORT_SYMBOL_GPL(pmi_send_message);
> ...
> > +EXPORT_SYMBOL_GPL(pmi_register_handler);
> ...
> > +EXPORT_SYMBOL_GPL(pmi_unregister_handler);
> 
> Are the symbol exports necessary?
> 
> <snip>
> 
> > +void pmi_register_handler(struct of_device *, struct pmi_handler *);
> > +void pmi_unregister_handler(struct of_device *, struct pmi_handler *);
> > +
> > +void pmi_send_message(struct of_device *, struct pmi_message *);
> 
> Are there users of these functions?
> 

yes, they will be used by the cbe_cpufreq driver.
I will send a patch for it, as soon as i was able to test it,
hopefully today or tomorrow.

-- 
Mit freundlichen Grüssen,
kind regards,

Christian Krafft
IBM Systems & Technology Group, 
Linux Kernel Development
IT Specialist