Re: [Xen-devel] [PATCH 2/2] ns16550: Add compatible string for Raspberry Pi 4

[Julien Grall <julien.grall@xxxxxxx>]

(+ Andre)

Hi Stewart,

On 24/07/2019 15:34, Stewart Hildebrand wrote:
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxxxxxxxxxx>
>
> ---
>
> xen/drivers/char/ns16550.c | 1 +
>
> 1 file changed, 1 insertion(+)
>
> diff --git a/xen/drivers/char/ns16550.c b/xen/drivers/char/ns16550.c
>
> index e518f2d790..c8d7c9b710 100644
>
> --- a/xen/drivers/char/ns16550.c
>
> +++ b/xen/drivers/char/ns16550.c
>
> @@ -1611,6 +1611,7 @@ static const struct dt_device_match ns16550_dt_match[] 
> __initconst =
>       DT_MATCH_COMPATIBLE("ns16550"),
>
>       DT_MATCH_COMPATIBLE("ns16550a"),
>
>       DT_MATCH_COMPATIBLE("snps,dw-apb-uart"),
>
> +    DT_MATCH_COMPATIBLE("brcm,bcm2835-aux-uart"),
A different compatible usually means the UART behaves differently. So your 
commit message should at least explain what are the differences and why this is 
not necessary for Xen.
Looking at your repo xen-rpi4-builder, you are hacking the UART DT node. The new 
properties are not part of the binding for that compatible (see [1]).
While it is inevitable to hack device-tree for a first port, I don't want Xen to 
require unofficial binding.
Instead, those property should be set in the driver when matching 
brcm,bcm2835-aux-uart.
Cheers,

[1] Documentation/devicetree/bindings/serial/brcm,bcm2835-aux-uart.txt

>       { /* sentinel */ },
>
> };
>
> --
>
> 2.22.0
--
Julien Grall

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