netdev - Re: [PATCH -next] smsc911x: Fix crash seen if neither ACPI nor OF is configured or used

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Message-ID: <55DDF939.9050209@roeck-us.net>
Date:	Wed, 26 Aug 2015 10:36:57 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Tony Lindgren <tony@...mide.com>
CC:	Steve Glendinning <steve.glendinning@...well.net>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jeremy Linton <jeremy.linton@....com>,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH -next] smsc911x: Fix crash seen if neither ACPI nor OF
 is configured or used

Hi Tony,

On 08/26/2015 10:04 AM, Tony Lindgren wrote:
> Hi,
>
> * Guenter Roeck <linux@...ck-us.net> [150817 13:48]:
>> Commit 0b50dc4fc971 ("Convert smsc911x to use ACPI as well as DT") makes
>> the call to smsc911x_probe_config() unconditional, and no longer fails if
>> there is no device node. device_get_phy_mode() is called unconditionally,
>> and if there is no phy node configured returns an error code. This error
>> code is assigned to phy_interface, and interpreted elsewhere in the code
>> as valid phy mode. This in turn causes qemu to crash when running a
>> variant of realview_pb_defconfig.
>>
>> 	qemu: hardware error: lan9118_read: Bad reg 0x86
>>
>> Fixes: 0b50dc4fc971 ("Convert smsc911x to use ACPI as well as DT")
>> Cc: Jeremy Linton <jeremy.linton@....com>
>> Cc Graeme Gregory <graeme.gregory@...aro.org>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>>   drivers/net/ethernet/smsc/smsc911x.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/ethernet/smsc/smsc911x.c b/drivers/net/ethernet/smsc/smsc911x.c
>> index 0f21aa3bb537..34f97684506b 100644
>> --- a/drivers/net/ethernet/smsc/smsc911x.c
>> +++ b/drivers/net/ethernet/smsc/smsc911x.c
>> @@ -2367,12 +2367,17 @@ static const struct smsc911x_ops shifted_smsc911x_ops = {
>>   static int smsc911x_probe_config(struct smsc911x_platform_config *config,
>>   				 struct device *dev)
>>   {
>> +	int phy_interface;
>>   	u32 width = 0;
>>
>>   	if (!dev)
>>   		return -ENODEV;
>>
>> -	config->phy_interface = device_get_phy_mode(dev);
>> +	phy_interface = device_get_phy_mode(dev);
>> +	if (phy_interface < 0)
>> +		return phy_interface;
>> +
>> +	config->phy_interface = phy_interface;
>>
>>   	device_get_mac_address(dev, config->mac, ETH_ALEN);
>
> Looks like this change makes at least omap boards using smsc911x
> fail with -22 for me in Linux next.
>

What do you see if you revert my patch ? It should assign -22, or its
unsigned representation, to phy_interface, which isn't such a good idea
either.

> Do any of the the device tree configured smsc911x devices actually
> have a phy configured?
>
Good question, and beats me. Looking into the original code,
it didn't check for an error return from of_get_phy_mode() either,
and thus _would_ dutifully assign the error code to phy_interface.
Wonder how was this supposed to work to start with.

I'll do some debugging and try to find out what exactly is going on.

Guenter

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