radeonsi: Add debug option to enable low latency encode

Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Reviewed-by: Boyuan Zhang <Boyuan.Zhang@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30039>

docs/envvars.rst

@@ -1524,6 +1524,8 @@ RadeonSI driver environment variables
       Disable DPBB. Overrules the dpbb enable option.
    ``noefc``
       Disable hardware based encoder color format conversion
+   ``lowlatencyenc``
+      Enable low latency encoding
    ``notiling``
       Disable tiling
    ``nofmask``

src/gallium/drivers/radeonsi/si_pipe.c

@@ -87,6 +87,7 @@ static const struct debug_named_value radeonsi_debug_options[] = {
 
    /* Multimedia options: */
    { "noefc", DBG(NO_EFC), "Disable hardware based encoder colour format conversion."},
+   {"lowlatencyenc", DBG(LOW_LATENCY_ENCODE), "Enable low latency encoding."},
 
    /* 3D engine options: */
    {"nongg", DBG(NO_NGG), "Disable NGG and use the legacy pipeline."},

src/gallium/drivers/radeonsi/si_pipe.h

@@ -212,6 +212,7 @@ enum
 
    /* Multimedia options: */
    DBG_NO_EFC,
+   DBG_LOW_LATENCY_ENCODE,
 
    /* 3D engine options: */
    DBG_NO_NGG,