[Xen-devel] [PATCH] 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>
---
 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..31b7d56d7d 100644
--- a/xen/arch/arm/vpl011.c
+++ b/xen/arch/arm/vpl011.c
@@ -626,6 +626,8 @@ int domain_vpl011_init(struct domain *d, struct 
vpl011_init_info *info)
     if ( vpl011->backend.dom.ring_buf )
         return -EINVAL;
 
+    vpl011->uartfr = TXFE | RXFE;
+
     /*
      * info is NULL when the backend is in Xen.
      * info is != NULL when the backend is in a domain.
-- 
2.17.1


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