This patch fixes "Ooops, address error on load or ifetch!",
caused by "usb" command on MIPS architecture.
To reproduce the problem follow the following steps:
1. Build barebox for MIPS target with -O0 optimization flag:
diff --git a/Makefile b/Makefile
index 5a7fd5f..da9a8be 100644
--- a/Makefile
+++ b/Makefile
@@ -301,7 +301,7 @@ CPPFLAGS := -D__KERNEL__ -D__BAREBOX__ $(LINUXINCLUDE) -fno-builtin -ffre
CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs \
-Werror-implicit-function-declaration \
- -fno-strict-aliasing -fno-common -Os -pipe
+ -fno-strict-aliasing -fno-common -O0 -pipe
AFLAGS := -D__ASSEMBLY__
LDFLAGS_barebox := -Map barebox.map
2. Plug in a usb flash drive.
3. Run the "usb" command:
barebox@QEMU DUNA:/ usb -s
USB: scanning bus for devices...
&(dev->config.interface[0].ep_desc[0].wMaxPacketSize) = a042732a
Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
&(dev->config.interface[0].ep_desc[0].wMaxPacketSize) = a0429f02
&(dev->config.interface[0].ep_desc[1].wMaxPacketSize) = a0429f0b
Ooops, address error on load or ifetch!
$ 0 : 00000000 00000000 a0429f0b a0429de4
$ 4 : 00000000 0000000a 00000000 000687e0
$ 8 : 00000000 00000000 00000000 fa000000
$12 : 00000001 00000004 00000000 00000000
$16 : 00000000 00000000 00000000 00000000
$20 : 00000000 00000000 00000000 00000000
$24 : 00000000 00000000
$28 : 00000000 a03ffb40 a03ffb40 a082e9f4
Hi : 00000000
Lo : 00000000
epc : a082ea38
ra : a082e9f4
Status: b4000002
Cause : 00008010
Config: 88d0c083
### ERROR ### Please RESET the board ###
The source of the error is the following line of code from the usb_parse_config() function:
le16_to_cpus(&(dev->config.interface[ifno].ep_desc[epno].\
wMaxPacketSize));
Which tries to load half-word from an un-aligned address 0xa0429f0b stored in v0:
a082ea38: 94420000 lhu v0,0(v0)
0xa0429f0b is an address of wMaxPacketSize member of a struct usb_endpoint_descriptor at offset 4:
struct usb_endpoint_descriptor {
__u8 bLength;
__u8 bDescriptorType;
__u8 bEndpointAddress;
__u8 bmAttributes;
__le16 wMaxPacketSize;
__u8 bInterval;
__u8 bRefresh;
__u8 bSynchAddress;
} __attribute__ ((packed));
The instances of the usb_endpoint_descriptor are stored in a "ep_desc" array:
struct usb_interface {
...
struct usb_endpoint_descriptor ep_desc[USB_MAXENDPOINTS];
};
Since the size of the usb_endpoint_descriptor is odd (9 bytes),
the second element of the ep_desc array is un-aligned,
as well as it's member wMaxPacketSize:
Bus 001 Device 001: ID 0000:0000 EHCI Host Controller
&(dev->config.interface[0].ep_desc[0].wMaxPacketSize) = a0429f02
&(dev->config.interface[0].ep_desc[1].wMaxPacketSize) = a0429f0b
A possible fix to this problem is to make the size of the usb_endpoint_descriptor even.
---
include/usb/ch9.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/usb/ch9.h b/include/usb/ch9.h
index ab5d531..5b261e6 100644
--- a/include/usb/ch9.h
+++ b/include/usb/ch9.h
@@ -379,6 +379,7 @@ struct usb_endpoint_descriptor {
/* use USB_DT_ENDPOINT*_SIZE in bLength, not sizeof. */
__u8 bRefresh;
__u8 bSynchAddress;
+ __u8 fill;
} __attribute__ ((packed));
#define USB_DT_ENDPOINT_SIZE 7
--
2.1.4
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