From bd43a9844bc6f78e00fdc91db47f6969d10c5ac5 Mon Sep 17 00:00:00 2001 From: Alexander Stein Date: Thu, 8 Dec 2022 07:55:38 +0100 Subject: drm: bridge: ldb: Warn if LDB clock does not match requested link frequency The LDB clock needs to be exactly 7-times the pixel clock used by the display. Signed-off-by: Alexander Stein Reviewed-by: Neil Armstrong Signed-off-by: Neil Armstrong Link: https://patchwork.freedesktop.org/patch/msgid/20221208065538.1753666-1-alexander.stein@ew.tq-group.com --- drivers/gpu/drm/bridge/fsl-ldb.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/bridge/fsl-ldb.c b/drivers/gpu/drm/bridge/fsl-ldb.c index f9e0f8d99268..9bcba8fc57e7 100644 --- a/drivers/gpu/drm/bridge/fsl-ldb.c +++ b/drivers/gpu/drm/bridge/fsl-ldb.c @@ -66,6 +66,14 @@ static inline struct fsl_ldb *to_fsl_ldb(struct drm_bridge *bridge) return container_of(bridge, struct fsl_ldb, bridge); } +static unsigned long fsl_ldb_link_frequency(struct fsl_ldb *fsl_ldb, int clock) +{ + if (fsl_ldb->lvds_dual_link) + return clock * 3500; + else + return clock * 7000; +} + static int fsl_ldb_attach(struct drm_bridge *bridge, enum drm_bridge_attach_flags flags) { @@ -85,6 +93,8 @@ static void fsl_ldb_atomic_enable(struct drm_bridge *bridge, const struct drm_display_mode *mode; struct drm_connector *connector; struct drm_crtc *crtc; + unsigned long configured_link_freq; + unsigned long requested_link_freq; bool lvds_format_24bpp; bool lvds_format_jeida; u32 reg; @@ -128,10 +138,15 @@ static void fsl_ldb_atomic_enable(struct drm_bridge *bridge, crtc_state = drm_atomic_get_new_crtc_state(state, crtc); mode = &crtc_state->adjusted_mode; - if (fsl_ldb->lvds_dual_link) - clk_set_rate(fsl_ldb->clk, mode->clock * 3500); - else - clk_set_rate(fsl_ldb->clk, mode->clock * 7000); + requested_link_freq = fsl_ldb_link_frequency(fsl_ldb, mode->clock); + clk_set_rate(fsl_ldb->clk, requested_link_freq); + + configured_link_freq = clk_get_rate(fsl_ldb->clk); + if (configured_link_freq != requested_link_freq) + dev_warn(fsl_ldb->dev, "Configured LDB clock (%lu Hz) does not match requested LVDS clock: %lu Hz", + configured_link_freq, + requested_link_freq); + clk_prepare_enable(fsl_ldb->clk); /* Program LDB_CTRL */ -- cgit v1.2.3