[Xen-devel] [PATCH v2] xen/arm: initialize vpl011 flag register

[Jeff Kubascik <jeff.kubascik@xxxxxxxxxxxxxxx>]

The tx/rx fifo flags were not set when the vpl011 is initialized. This
is a problem for certain guests that are operating in polled mode, as a
guest will generally check the rx fifo empty flag to determine if there
is data before doing a read. The result is a continuous spam of the
message "vpl011: Unexpected IN ring buffer empty" before the first valid
character is received. This initializes the flag status register to the
default specified in the PL011 technical reference manual.

Signed-off-by: Jeff Kubascik <jeff.kubascik@xxxxxxxxxxxxxxx>

Changes in v2:
- Moved uartfr initialization to later point in function after potential
return/failure points
---
 xen/arch/arm/vpl011.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/arm/vpl011.c b/xen/arch/arm/vpl011.c
index 7bc5eeb207..895f436cc4 100644
--- a/xen/arch/arm/vpl011.c
+++ b/xen/arch/arm/vpl011.c
@@ -668,6 +668,8 @@ int domain_vpl011_init(struct domain *d, struct 
vpl011_init_info *info)
         goto out2;
     }
 
+    vpl011->uartfr = TXFE | RXFE;
+
     spin_lock_init(&vpl011->lock);
 
     register_mmio_handler(d, &vpl011_mmio_handler,
-- 
2.17.1


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