drm/amd/display: Reset DMUB mailbox SW state after HW reset

[Why]
Otherwise we can be out of sync with what's in the hardware, leading
to us rerunning every command that's presently in the ringbuffer.

[How]
Reset software state for the mailboxes in hw_reset callback.
This is already done as part of the mailbox init in hw_init, but we
do need to remember to reset the last cached wptr value as well here.

Reviewed-by: Hansen Dsouza <[e-mail]>
Acked-by: Alex Hung <[e-mail]>
Signed-off-by: Nicholas Kazlauskas <[e-mail]>
Tested-by: Daniel Wheeler <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/display/dmub/src/dmub_srv.c

···
 	if (dmub->hw_funcs.reset)
 		dmub->hw_funcs.reset(dmub);
 
+	/* reset the cache of the last wptr as well now that hw is reset */
+	dmub->inbox1_last_wptr = 0;
+
 	cw0.offset.quad_part = inst_fb->gpu_addr;
 	cw0.region.base = DMUB_CW0_BASE;
 	cw0.region.top = cw0.region.base + inst_fb->size - 1;
···
 
 	if (dmub->hw_funcs.reset)
 		dmub->hw_funcs.reset(dmub);
+
+	/* mailboxes have been reset in hw, so reset the sw state as well */
+	dmub->inbox1_last_wptr = 0;
+	dmub->inbox1_rb.wrpt = 0;
+	dmub->inbox1_rb.rptr = 0;
+	dmub->outbox0_rb.wrpt = 0;
+	dmub->outbox0_rb.rptr = 0;
+	dmub->outbox1_rb.wrpt = 0;
+	dmub->outbox1_rb.rptr = 0;
 
 	dmub->hw_init = false;