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From: Andy Shevchenko <andy.shevchenko@gmail.com>
Date: Sat, 11 May 2024 08:42:46 +0300
To: Krishna Kumar <krishnak@linux.ibm.com>
Cc: mpe@ellerman.id.au, npiggin@gmail.com, linuxppc-dev@lists.ozlabs.org,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	brking@linux.vnet.ibm.com, gbatra@linux.ibm.com,
	aneesh.kumar@kernel.org, christophe.leroy@csgroup.eu,
	nathanl@linux.ibm.com, bhelgaas@google.com, oohall@gmail.com,
	tpearson@raptorengineering.com, mahesh.salgaonkar@in.ibm.com
Subject: Re: [PATCH 2/2] arch/powerpc: hotplug driver bridge support
Message-ID: <Zj8FVva9G9_r6-cZ@surfacebook.localdomain>
References: <20240509120644.653577-1-krishnak@linux.ibm.com>
 <20240509120644.653577-3-krishnak@linux.ibm.com>
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In-Reply-To: <20240509120644.653577-3-krishnak@linux.ibm.com>

Thu, May 09, 2024 at 05:35:54PM +0530, Krishna Kumar kirjoitti:
> There is an issue with the hotplug operation when it's done on the
> bridge/switch slot. The bridge-port and devices behind the bridge, which
> become offline by hot-unplug operation, don't get hot-plugged/enabled by
> doing hot-plug operation on that slot. Only the first port of the bridge
> gets enabled and the remaining port/devices remain unplugged. The hot
> plug/unplug operation is done by the hotplug driver
> (drivers/pci/hotplug/pnv_php.c).
> 
> Root Cause Analysis: This behavior is due to missing code for the DPC
> switch/bridge. The existing driver depends on pci_hp_add_devices()
> function for device enablement. This function calls pci_scan_slot() on
> only one device-node/port of the bridge, not on all the siblings'
> device-node/port.
> 
> The missing code needs to be added which will find all the sibling
> device-nodes/bridge-ports and will run explicit pci_scan_slot() on
> those.  A new function has been added for this purpose which gets
> invoked from pci_hp_add_devices(). This new function
> pci_traverse_sibling_nodes_and_scan_slot() gets all the sibling
> bridge-ports by traversal and explicitly invokes pci_scan_slot on them.
> 
> 

One blank line is enough here.

> Signed-off-by: Krishna Kumar <krishnak@linux.ibm.com>

..

> +void *pci_traverse_sibling_nodes_and_scan_slot(struct device_node *start, struct pci_bus *bus)
> +{
> +	struct device_node *dn;
> +	struct device_node *parent;
> +	int slotno;
> +
> +	const __be32 *classp1;
> +	u32 class1 = 0;

> +	classp1 = of_get_property(start->child, "class-code", NULL);
> +	if (classp1)
> +		class1 = of_read_number(classp1, 1);

What's wrong with of_property_read_u32()?


> +	/* Call of pci_scan_slot for non-bridge/EP case */
> +	if (!((class1 >> 8) == PCI_CLASS_BRIDGE_PCI)) {
> +		slotno = PCI_SLOT(PCI_DN(start->child)->devfn);
> +		pci_scan_slot(bus, PCI_DEVFN(slotno, 0));
> +		return NULL;
> +	}
> +
> +	/* Iterate all siblings */
> +	parent = start;
> +	for_each_child_of_node(parent, dn) {
> +		const __be32 *classp;
> +		u32 class = 0;
> +
> +		classp = of_get_property(dn, "class-code", NULL);
> +		if (classp)
> +			class = of_read_number(classp, 1);

Ditto.

> +		/* Call of pci_scan_slot on each sibling-nodes/bridge-ports */
> +		if ((class >> 8) == PCI_CLASS_BRIDGE_PCI) {
> +			slotno = PCI_SLOT(PCI_DN(dn)->devfn);
> +			pci_scan_slot(bus, PCI_DEVFN(slotno, 0));
> +		}
> +	}
> +
> +	return NULL;
> +}

-- 
With Best Regards,
Andy Shevchenko