[PATCH RESEND v5 10/25] drm/msm/dp: Always program MST_FIFO_CONSTANT_FILL for MST use cases
From: Yongxing Mou
Date: Mon Jun 29 2026 - 10:37:26 EST
From: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
As per the hardware programming guide, MST_FIFO_CONSTANT_FILL must
always be programmed when operating in MST mode. Ensure the register
is configured accordingly.
Signed-off-by: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
Signed-off-by: Yongxing Mou <yongxing.mou@xxxxxxxxxxxxxxxx>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/msm/dp/dp_ctrl.c | 2 ++
drivers/gpu/drm/msm/dp/dp_panel.c | 12 ++++++++++++
drivers/gpu/drm/msm/dp/dp_panel.h | 2 ++
3 files changed, 16 insertions(+)
diff --git a/drivers/gpu/drm/msm/dp/dp_ctrl.c b/drivers/gpu/drm/msm/dp/dp_ctrl.c
index c4f1a68b1210..80116e19fbbf 100644
--- a/drivers/gpu/drm/msm/dp/dp_ctrl.c
+++ b/drivers/gpu/drm/msm/dp/dp_ctrl.c
@@ -677,6 +677,8 @@ static void msm_dp_ctrl_configure_source_params(struct msm_dp_ctrl_private *ctrl
msm_dp_ctrl_config_misc1_misc0(ctrl, panel);
msm_dp_panel_timing_cfg(panel, ctrl->msm_dp_ctrl.wide_bus_en);
+
+ msm_dp_panel_mst_async_fifo(panel, ctrl->mst_active);
}
/*
diff --git a/drivers/gpu/drm/msm/dp/dp_panel.c b/drivers/gpu/drm/msm/dp/dp_panel.c
index cbbcc0dbf652..ba5ee2ad8924 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.c
+++ b/drivers/gpu/drm/msm/dp/dp_panel.c
@@ -741,6 +741,18 @@ int msm_dp_panel_timing_cfg(struct msm_dp_panel *msm_dp_panel, bool wide_bus_en)
return 0;
}
+void msm_dp_panel_mst_async_fifo(struct msm_dp_panel *msm_dp_panel, bool mst_en)
+{
+ struct msm_dp_panel_private *panel;
+
+ panel = container_of(msm_dp_panel, struct msm_dp_panel_private, msm_dp_panel);
+
+ if (mst_en)
+ msm_dp_write_pn(panel, MMSS_DP_ASYNC_FIFO_CONFIG, 0x01);
+ else
+ msm_dp_write_pn(panel, MMSS_DP_ASYNC_FIFO_CONFIG, 0x00);
+}
+
int msm_dp_panel_init_panel_info(struct msm_dp_panel *msm_dp_panel,
const struct drm_display_mode *adjusted_mode,
u32 bpp)
diff --git a/drivers/gpu/drm/msm/dp/dp_panel.h b/drivers/gpu/drm/msm/dp/dp_panel.h
index 3e78af9e430d..edc39ee5268e 100644
--- a/drivers/gpu/drm/msm/dp/dp_panel.h
+++ b/drivers/gpu/drm/msm/dp/dp_panel.h
@@ -73,6 +73,8 @@ void msm_dp_panel_clear_dsc_dto(struct msm_dp_panel *msm_dp_panel);
void msm_dp_panel_enable_vsc_sdp(struct msm_dp_panel *msm_dp_panel, struct dp_sdp *vsc_sdp);
void msm_dp_panel_disable_vsc_sdp(struct msm_dp_panel *msm_dp_panel);
+void msm_dp_panel_mst_async_fifo(struct msm_dp_panel *msm_dp_panel, bool mst_en);
+
/**
* is_link_rate_valid() - validates the link rate
* @bw_code: link rate requested by the sink
--
2.43.0