drm/amd/display: Try RGB before YCbCr 4:4:4 in stream validationgrafted

amdgpu_dm_create_validate_stream_for_sink() walks encoding_order[] and
uses the first encoding that validates. YCbCr 4:4:4 is listed before
RGB, so an HDMI sink that advertises 4:4:4 gets YCbCr 4:4:4 whenever the
"color format" property is left at AUTO, even though RGB fits the same
link.

That contradicts the documented AUTO behaviour for HDMI in enum
drm_connector_color_format (RGB, falling back to YCbCr 4:2:0 only when
the bandwidth is not available or the mode is 4:2:0-only), which the
amdgpu implementation of the property also describes. It also leaves
the "Broadcast RGB" property without effect on such sinks, since the
quantization range it selects only applies to RGB output.

Try RGB first. The mask still holds every encoding the sink supports,
so a mode that cannot carry RGB falls back exactly as before.

For reference, v7.2 picked RGB here unless YCbCr 4:4:4 was forced
through debugfs, while earlier kernels picked YCbCr 4:4:4 for any HDMI
sink that advertised it.

Fixes: 0b0ff65d3ca1 ("drm/amd/display: Refactor stream validation")
Suggested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Assisted-by: Claude Code:claude-fable-5-1
Signed-off-by: Adrian Betschart <adrian.betschart@cinemaone.ch>
Reviewed-by: Fangzhi Zuo <jerry.zuo@amd.com>
Tested-by: Adolfo Rodrigues <adolfotregosa@gmail.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 7de432bc753133764dc40d37f9388da56de251e7)

1 files changed, 238 insertions, 0 deletions

diff --git a/Documentation/bpf/map_devmap.rst b/Documentation/bpf/map_devmap.rst
new file mode 100644
index 000000000..927312c7b
--- /dev/null
+++ b/Documentation/bpf/map_devmap.rst
@@ -0,0 +1,238 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+.. Copyright (C) 2022 Red Hat, Inc.
+
+=================================================
+BPF_MAP_TYPE_DEVMAP and BPF_MAP_TYPE_DEVMAP_HASH
+=================================================
+
+.. note::
+   - ``BPF_MAP_TYPE_DEVMAP`` was introduced in kernel version 4.14
+   - ``BPF_MAP_TYPE_DEVMAP_HASH`` was introduced in kernel version 5.4
+
+``BPF_MAP_TYPE_DEVMAP`` and ``BPF_MAP_TYPE_DEVMAP_HASH`` are BPF maps primarily
+used as backend maps for the XDP BPF helper call ``bpf_redirect_map()``.
+``BPF_MAP_TYPE_DEVMAP`` is backed by an array that uses the key as
+the index to lookup a reference to a net device. While ``BPF_MAP_TYPE_DEVMAP_HASH``
+is backed by a hash table that uses a key to lookup a reference to a net device.
+The user provides either <``key``/ ``ifindex``> or <``key``/ ``struct bpf_devmap_val``>
+pairs to update the maps with new net devices.
+
+.. note::
+    - The key to a hash map doesn't have to be an ``ifindex``.
+    - While ``BPF_MAP_TYPE_DEVMAP_HASH`` allows for densely packing the net devices
+      it comes at the cost of a hash of the key when performing a look up.
+
+The setup and packet enqueue/send code is shared between the two types of
+devmap; only the lookup and insertion is different.
+
+Usage
+=====
+Kernel BPF
+----------
+bpf_redirect_map()
+^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+    long bpf_redirect_map(struct bpf_map *map, u32 key, u64 flags)
+
+Redirect the packet to the endpoint referenced by ``map`` at index ``key``.
+For ``BPF_MAP_TYPE_DEVMAP`` and ``BPF_MAP_TYPE_DEVMAP_HASH`` this map contains
+references to net devices (for forwarding packets through other ports).
+
+The lower two bits of *flags* are used as the return code if the map lookup
+fails. This is so that the return value can be one of the XDP program return
+codes up to ``XDP_TX``, as chosen by the caller. The higher bits of ``flags``
+can be set to ``BPF_F_BROADCAST`` or ``BPF_F_EXCLUDE_INGRESS`` as defined
+below.
+
+With ``BPF_F_BROADCAST`` the packet will be broadcast to all the interfaces
+in the map, with ``BPF_F_EXCLUDE_INGRESS`` the ingress interface will be excluded
+from the broadcast.
+
+.. note::
+    - The key is ignored if BPF_F_BROADCAST is set.
+    - The broadcast feature can also be used to implement multicast forwarding:
+      simply create multiple DEVMAPs, each one corresponding to a single multicast group.
+
+This helper will return ``XDP_REDIRECT`` on success, or the value of the two
+lower bits of the ``flags`` argument if the map lookup fails.
+
+More information about redirection can be found :doc:`redirect`
+
+bpf_map_lookup_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+   void *bpf_map_lookup_elem(struct bpf_map *map, const void *key)
+
+Net device entries can be retrieved using the ``bpf_map_lookup_elem()``
+helper.
+
+User space
+----------
+.. note::
+    DEVMAP entries can only be updated/deleted from user space and not
+    from an eBPF program. Trying to call these functions from a kernel eBPF
+    program will result in the program failing to load and a verifier warning.
+
+bpf_map_update_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+   int bpf_map_update_elem(int fd, const void *key, const void *value, __u64 flags);
+
+Net device entries can be added or updated using the ``bpf_map_update_elem()``
+helper. This helper replaces existing elements atomically. The ``value`` parameter
+can be ``struct bpf_devmap_val`` or a simple ``int ifindex`` for backwards
+compatibility.
+
+ .. code-block:: c
+
+    struct bpf_devmap_val {
+        __u32 ifindex;   /* device index */
+        union {
+            int   fd;  /* prog fd on map write */
+            __u32 id;  /* prog id on map read */
+        } bpf_prog;
+    };
+
+The ``flags`` argument can be one of the following:
+  - ``BPF_ANY``: Create a new element or update an existing element.
+  - ``BPF_NOEXIST``: Create a new element only if it did not exist.
+  - ``BPF_EXIST``: Update an existing element.
+
+DEVMAPs can associate a program with a device entry by adding a ``bpf_prog.fd``
+to ``struct bpf_devmap_val``. Programs are run after ``XDP_REDIRECT`` and have
+access to both Rx device and Tx device. The  program associated with the ``fd``
+must have type XDP with expected attach type ``xdp_devmap``.
+When a program is associated with a device index, the program is run on an
+``XDP_REDIRECT`` and before the buffer is added to the per-cpu queue. Examples
+of how to attach/use xdp_devmap progs can be found in the kernel selftests:
+
+- ``tools/testing/selftests/bpf/prog_tests/xdp_devmap_attach.c``
+- ``tools/testing/selftests/bpf/progs/test_xdp_with_devmap_helpers.c``
+
+bpf_map_lookup_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+.. c:function::
+   int bpf_map_lookup_elem(int fd, const void *key, void *value);
+
+Net device entries can be retrieved using the ``bpf_map_lookup_elem()``
+helper.
+
+bpf_map_delete_elem()
+^^^^^^^^^^^^^^^^^^^^^
+.. code-block:: c
+
+.. c:function::
+   int bpf_map_delete_elem(int fd, const void *key);
+
+Net device entries can be deleted using the ``bpf_map_delete_elem()``
+helper. This helper will return 0 on success, or negative error in case of
+failure.
+
+Examples
+========
+
+Kernel BPF
+----------
+
+The following code snippet shows how to declare a ``BPF_MAP_TYPE_DEVMAP``
+called tx_port.
+
+.. code-block:: c
+
+    struct {
+        __uint(type, BPF_MAP_TYPE_DEVMAP);
+        __type(key, __u32);
+        __type(value, __u32);
+        __uint(max_entries, 256);
+    } tx_port SEC(".maps");
+
+The following code snippet shows how to declare a ``BPF_MAP_TYPE_DEVMAP_HASH``
+called forward_map.
+
+.. code-block:: c
+
+    struct {
+        __uint(type, BPF_MAP_TYPE_DEVMAP_HASH);
+        __type(key, __u32);
+        __type(value, struct bpf_devmap_val);
+        __uint(max_entries, 32);
+    } forward_map SEC(".maps");
+
+.. note::
+
+    The value type in the DEVMAP above is a ``struct bpf_devmap_val``
+
+The following code snippet shows a simple xdp_redirect_map program. This program
+would work with a user space program that populates the devmap ``forward_map`` based
+on ingress ifindexes. The BPF program (below) is redirecting packets using the
+ingress ``ifindex`` as the ``key``.
+
+.. code-block:: c
+
+    SEC("xdp")
+    int xdp_redirect_map_func(struct xdp_md *ctx)
+    {
+        int index = ctx->ingress_ifindex;
+
+        return bpf_redirect_map(&forward_map, index, 0);
+    }
+
+The following code snippet shows a BPF program that is broadcasting packets to
+all the interfaces in the ``tx_port`` devmap.
+
+.. code-block:: c
+
+    SEC("xdp")
+    int xdp_redirect_map_func(struct xdp_md *ctx)
+    {
+        return bpf_redirect_map(&tx_port, 0, BPF_F_BROADCAST | BPF_F_EXCLUDE_INGRESS);
+    }
+
+User space
+----------
+
+The following code snippet shows how to update a devmap called ``tx_port``.
+
+.. code-block:: c
+
+    int update_devmap(int ifindex, int redirect_ifindex)
+    {
+        int ret;
+
+        ret = bpf_map_update_elem(bpf_map__fd(tx_port), &ifindex, &redirect_ifindex, 0);
+        if (ret < 0) {
+            fprintf(stderr, "Failed to update devmap_ value: %s\n",
+                strerror(errno));
+        }
+
+        return ret;
+    }
+
+The following code snippet shows how to update a hash_devmap called ``forward_map``.
+
+.. code-block:: c
+
+    int update_devmap(int ifindex, int redirect_ifindex)
+    {
+        struct bpf_devmap_val devmap_val = { .ifindex = redirect_ifindex };
+        int ret;
+
+        ret = bpf_map_update_elem(bpf_map__fd(forward_map), &ifindex, &devmap_val, 0);
+        if (ret < 0) {
+            fprintf(stderr, "Failed to update devmap_ value: %s\n",
+                strerror(errno));
+        }
+        return ret;
+    }
+
+References
+===========
+
+- https://lwn.net/Articles/728146/
+- https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=6f9d451ab1a33728adb72d7ff66a7b374d665176
+- https://elixir.bootlin.com/linux/latest/source/net/core/filter.c#L4106