From: Chen-Yu Tsai wenst@chromium.org

[ Upstream commit 32c9c06adb5b157ef259233775a063a43746d699 ]

On Chromebooks based on Mediatek MT8195 or MT8188, the audio frontend (AFE) is limited to accessing a very small window (1 MiB) of memory, which is described as a reserved memory region in the device tree.

On these two platforms, the maximum buffer size is given as 512 KiB. The MediaTek common code uses the same value for preallocations. This means that only the first two PCM substreams get preallocations, and then the whole space is exhausted, barring any other substreams from working. Since the substreams used are not always the first two, this means audio won't work correctly.

This is observed on the MT8188 Geralt Chromebooks, on which the "mediatek,dai-link" property was dropped when it was upstreamed. That property causes the driver to only register the PCM substreams listed in the property, and in the order given.

Instead of trying to compute an optimal value and figuring out which streams are used, simply disable preallocation. The PCM buffers are managed by the core and are allocated and released on the fly. There should be no impact to any of the other MediaTek platforms.

Signed-off-by: Chen-Yu Tsai wenst@chromium.org Reviewed-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Link: https://patch.msgid.link/20241219105303.548437-1-wenst@chromium.org Signed-off-by: Mark Brown broonie@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- sound/soc/mediatek/common/mtk-afe-platform-driver.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/soc/mediatek/common/mtk-afe-platform-driver.c b/sound/soc/mediatek/common/mtk-afe-platform-driver.c index 01501d5747a7..52495c930ca3 100644 --- a/sound/soc/mediatek/common/mtk-afe-platform-driver.c +++ b/sound/soc/mediatek/common/mtk-afe-platform-driver.c @@ -120,8 +120,8 @@ int mtk_afe_pcm_new(struct snd_soc_component *component, struct mtk_base_afe *afe = snd_soc_component_get_drvdata(component);

size = afe->mtk_afe_hardware->buffer_bytes_max; - snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_DEV, - afe->dev, size, size); + snd_pcm_set_managed_buffer_all(pcm, SNDRV_DMA_TYPE_DEV, afe->dev, 0, size); + return 0; } EXPORT_SYMBOL_GPL(mtk_afe_pcm_new);