Subject: Re: [PATCH 4/4] drivers/pci/hotplug: Support surprise hotplug

From: Bjorn Helgaas <[email-masked]>
Date: Wed, 21 Sep 2016 11:57:03 -0500

Hi Gavin,

You don't need my ack for any of these, and I assume you'll merge them
through the powerpc tree.

Minor comments below, feel free to ignore them.

On Wed, Sep 21, 2016 at 10:15:30PM +1000, Gavin Shan wrote:
> ...
> @@ -536,9 +565,16 @@ static struct pnv_php_slot *pnv_php_alloc_slot(struct device_node *dn)
>  	if (unlikely(!php_slot))
>  		return NULL;
>  
> +	php_slot->event = kzalloc(sizeof(struct pnv_php_event), GFP_KERNEL);
> +	if (unlikely(!php_slot->event)) {
> +		kfree(php_slot);
> +		return NULL;
> +	}

Since you *always* allocate the event when allocating the php_slot,
making the event a member of php_slot (instead of keeping a pointer to
it) would simplify your memory management a bit.

It seems to be the style in this file to use "unlikely" liberally, but
I really doubt there's any performance consideration in this code.  To
me it adds more clutter than usefulness.

> +static irqreturn_t pnv_php_interrupt(int irq, void *data)
> +{
> +	struct pnv_php_slot *php_slot = data;
> +	struct pci_dev *pchild, *pdev = php_slot->pdev;
> +	struct eeh_dev *edev;
> +	struct eeh_pe *pe;
> +	struct pnv_php_event *event;
> +	u16 sts, lsts;
> +	u8 presence;
> +	bool added;
> +	unsigned long flags;
> +	int ret;
> +
> +	pcie_capability_read_word(pdev, PCI_EXP_SLTSTA, &sts);
> +	sts &= (PCI_EXP_SLTSTA_PDC | PCI_EXP_SLTSTA_DLLSC);
> +	pcie_capability_write_word(pdev, PCI_EXP_SLTSTA, sts);

I didn't realize that this is some sort of hybrid of native PCIe
hotplug and PowerNV-specific stuff.  Wonder if there's any opportunity
to combine with or leverage pciehp.  That seems pretty blue-sky
though, since there's so much PowerNV special sauce here.

Bjorn