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

[Julien Grall <julien@xxxxxxx>]

Hi,

On 25/11/2019 20:58, Jeff Kubascik wrote:
> 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>
You could have retained my acked-by here :).

Acked-by: Julien Grall <julien@xxxxxxx>

We are in late stage for Xen 4.13 and from what you say this will only 
spam the console (though it is rate-limited). So I don't intend to 
request to be merged in Xen 4.13 (feel free to request it if you think 
it is worth it).
Instead, I will queue it for the next release in my branch for-next/4.14.

> Changes in v2:
> - Moved uartfr initialization to later point in function after potential
> return/failure points
We don't commit the changelog. To help making the committers life 
boring, I would recommend to add --- before it. git am will stripped 
anything after it.
> ---
Similar to this one.

>   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,
--
Julien Grall

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