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

From: Guenter Roeck
Date: Wed Aug 26 2015 - 13:37:08 EST

Hi Tony,

On 08/26/2015 10:04 AM, Tony Lindgren wrote:

* Guenter Roeck <linux@xxxxxxxxxxxx> [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@xxxxxxx>
Cc Graeme Gregory <graeme.gregory@xxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
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

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.


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