hw/net/can/sja1000: fix bug for single acceptance filter and standard frame

A CAN sja1000 standard frame filter mask has been computed and applied
incorrectly for standard frames when single Acceptance Filter Mode
(MOD_AFM = 1) has been selected. The problem has not been found
by Linux kernel testing because it uses dual filter mode (MOD_AFM = 0)
and leaves falters fully open.

The problem has been noticed by Grant Ramsay when testing with Zephyr
RTOS which uses single filter mode.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>
Reported-by: Grant Ramsay <gramsay@enphaseenergy.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2028
Fixes: 733210e754 ("hw/net/can: SJA1000 chip register level emulation")
Message-ID: <20240103231426.5685-1-pisa@fel.cvut.cz>

diff --git a/hw/net/can/can_sja1000.c b/hw/net/can/can_sja1000.c
index 1165d5982477e197c37440c10d574e2a83422241..6694d7bfd84abf2a4209ce7e24c9d53bb931e5f5 100644 (file)
--- a/hw/net/can/can_sja1000.c
+++ b/hw/net/can/can_sja1000.c
@@ -108,7 +108,7 @@ void can_sja_single_filter(struct qemu_can_filter *filter,
         }
 
         filter->can_mask = (uint32_t)amr[0] << 3;
-        filter->can_mask |= (uint32_t)amr[1] << 5;
+        filter->can_mask |= (uint32_t)amr[1] >> 5;
         filter->can_mask = ~filter->can_mask & QEMU_CAN_SFF_MASK;
         if (!(amr[1] & 0x10)) {
             filter->can_mask |= QEMU_CAN_RTR_FLAG;