Re: [PATCH V3 5/6] Avoid duplicate probe for of platform devices

On Fri, Jul 06, 2012 at 06:07:43AM +0000, Jia Hongtao-B38951 wrote:

quoted

-----Original Message-----
From: Greg KH [mailto:greg@kroah.com]
Sent: Friday, July 06, 2012 12:26 PM
To: Jia Hongtao-B38951
Cc: Rob Herring; devicetree-discuss@lists.ozlabs.org; linux-
kernel@vger.kernel.org; Li Yang-R58472
Subject: Re: [PATCH V3 5/6] Avoid duplicate probe for of platform devices

On Fri, Jul 06, 2012 at 02:05:05AM +0000, Jia Hongtao-B38951 wrote:

quoted

Hi Rob and Greg KH,

Do you have any better idea to avoid duplication probe warning?

I have no idea what the problem is that you are trying to solve.

quoted

quoted

On 06/08/2012 04:43 AM, Jia Hongtao wrote:

quoted

We changed the pcie controller driver to platform driver so that

the

quoted

quoted

PCI

quoted

of platform devices need to be created earlier in the arch_initcall

stage

quoted

according to the original timing of calling fsl_add_bridge(). So we

do

quoted

quoted

PCI

quoted

probing separately from other devices. But probing more than once

could

quoted

quoted

quoted

cause duplication warning. We add check if the devices have already

probed

quoted

before probing any devices to avoid duplication warning.

Ick, something else is going wrong here, how could you ever have the
same device probed more than once?

quoted

quoted

quoted

Signed-off-by: Jia Hongtao <redacted>
Signed-off-by: Li Yang <redacted>
---

Where's v1 and v2 history?

quoted

 drivers/of/platform.c |   18 ++++++++++++------
 1 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/of/platform.c b/drivers/of/platform.c
index a37330e..3aab01f 100644
--- a/drivers/of/platform.c
+++ b/drivers/of/platform.c

@@ -139,6 +139,18 @@ struct platform_device *of_device_alloc(struct

device_node *np,

quoted

 	if (!dev)
 		return NULL;

+	dev->dev.of_node = of_node_get(np);
+	if (bus_id)
+		dev_set_name(&dev->dev, "%s", bus_id);
+	else
+		of_device_make_bus_id(&dev->dev);
+
+	if (kset_find_obj(dev->dev.kobj.kset, kobject_name(&dev-

dev.kobj)))

Whatever you are trying to do here, odds are, it's wrong :)

What is happening that is causing the problem?  What is causing the
platform core to be calling probe on a device more than once?

greg k-h

This is why in some cases we may probe twice:
Firstly, we need to probe pci controller separately. But in KVM different
topology of device tree is used in which pci nodes are not under root node
but under "simple bus". Unfortunately, of_platform_bus_probe() will probe
all the first level nodes under "simple bus" so pci nodes will probe again.

Sounds like a bug :)

Two ways to solve this problem:
1. All the nodes that need to be probed should just under root.

That seems reasonable.

2. Avoid duplication probe at runtime like this patch did.

No, don't paper over the real problem in the platform core code like
this.  Fix the real issue here instead.

I do like the first one but it's hard to changing the traditional way that
exist for a long time.

I don't understand, why is this just showing up now?  What changed to
cause this?  Couldn't that be the real problem here?

greg k-h