Subject: Re: [PATCH] powernv/pci: Add PHB register dump debugfs handle

From: Gavin Shan <[email-masked]>
Date: Fri, 22 Jul 2016 16:36:55 +1000

On Fri, Jul 22, 2016 at 03:23:36PM +1000, Russell Currey wrote:
>On EEH events the kernel will print a dump of relevant registers.
>If EEH is unavailable (i.e. CONFIG_EEH is disabled, a new platform
>doesn't have EEH support, etc) this information isn't readily available.
>
>Add a new debugfs handler to trigger a PHB register dump, so that this
>information can be made available on demand.
>
>Signed-off-by: Russell Currey <[email-masked]>

Reviewed-by: Gavin Shan <[email-masked]>

>---
> arch/powerpc/platforms/powernv/pci-ioda.c | 35 +++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>index 891fc4a..ada2f3c 100644
>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>@@ -3018,6 +3018,38 @@ static void pnv_ioda_setup_pe_seg(struct pnv_ioda_pe *pe)
> 	}
> }
>
>+#ifdef CONFIG_DEBUG_FS
>+static ssize_t pnv_pci_debug_write(struct file *filp,
>+				   const char __user *user_buf,
>+				   size_t count, loff_t *ppos)
>+{
>+	struct pci_controller *hose = filp->private_data;
>+	struct pnv_phb *phb;
>+	int ret = 0;

Needn't initialize @ret in advance. The code might be simpler, but it's
only a personal preference:

	struct pci_controller *hose = filp->private_data;
	struct pnv_phb *phb = hose ? hose->private_data : NULL;

	if (!phb)
		return -ENODEV;

>+
>+	if (!hose)
>+		return -EFAULT;
>+
>+	phb = hose->private_data;
>+	if (!phb)
>+		return -EFAULT;
>+
>+	ret = opal_pci_get_phb_diag_data2(phb->opal_id, phb->diag.blob,
>+					  PNV_PCI_DIAG_BUF_SIZE);
>+
>+	if (!ret)
>+		pnv_pci_dump_phb_diag_data(phb->hose, phb->diag.blob);
>+
>+	return ret < 0 ? ret : count;

return ret == OPAL_SUCCESS ? count : -EIO;

>+}
>+
>+static const struct file_operations pnv_pci_debug_ops = {
>+	.open	= simple_open,
>+	.llseek	= no_llseek,
>+	.write	= pnv_pci_debug_write,

It might be reasonable to dump the diag-data on read if it is trying
to do it on write.

>+};
>+#endif /* CONFIG_DEBUG_FS */
>+
> static void pnv_pci_ioda_create_dbgfs(void)
> {
> #ifdef CONFIG_DEBUG_FS
>@@ -3036,6 +3068,9 @@ static void pnv_pci_ioda_create_dbgfs(void)
> 		if (!phb->dbgfs)
> 			pr_warning("%s: Error on creating debugfs on PHB#%x\n",
> 				__func__, hose->global_number);
>+
>+		debugfs_create_file("regdump", 0200, phb->dbgfs, hose,
>+				    &pnv_pci_debug_ops);

"diag-data" might be indicating or a better one you can name :)

Thanks,
Gavin

> 	}
> #endif /* CONFIG_DEBUG_FS */
> }
>-- 
>2.9.0
>