drm/sun4i: Force the mixer rate at 150MHz

It seems like the mixer can only run properly when clocked at 150MHz. In
order to have something more robust than simply a fire-and-forget
assigned-clocks-rate, let's put that in the code.

Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/f5f05307972ed05250e8094b302d68b9e7e167f6.1513854122.git-series.maxime.ripard@free-electrons.com

2 files changed, 13 insertions, 0 deletions

diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c b/drivers/gpu/drm/sun4i/sun8i_mixer.c
index 29ceeb016d72..3a610a87cbd2 100644
--- a/drivers/gpu/drm/sun4i/sun8i_mixer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c
@@ -398,6 +398,15 @@ static int sun8i_mixer_bind(struct device *dev, struct device *master,
                 ret = PTR_ERR(mixer->mod_clk);
                 goto err_disable_bus_clk;
         }
+
+        /*
+         * It seems that we need to enforce that rate for whatever
+         * reason for the mixer to be functional. Make sure it's the
+         * case.
+         */
+        if (mixer->cfg->mod_rate)
+                clk_set_rate(mixer->mod_clk, mixer->cfg->mod_rate);
+
         clk_prepare_enable(mixer->mod_clk);
 
         list_add_tail(&mixer->engine.list, &drv->engine_list);
@@ -474,6 +483,7 @@ static const struct sun8i_mixer_cfg sun8i_v3s_mixer_cfg = {
         .ui_num = 1,
         .scaler_mask = 0x3,
         .ccsc = 0,
+        .mod_rate = 150000000,
 };
 
 static const struct of_device_id sun8i_mixer_of_table[] = {
diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.h b/drivers/gpu/drm/sun4i/sun8i_mixer.h
index bc58040a88f9..f34e70c42adf 100644
--- a/drivers/gpu/drm/sun4i/sun8i_mixer.h
+++ b/drivers/gpu/drm/sun4i/sun8i_mixer.h
@@ -121,12 +121,15 @@ struct de2_fmt_info {
  *      Set value to 0 if this is first mixer or second mixer with VEP support.
  *      Set value to 1 if this is second mixer without VEP support. Other values
  *      are invalid.
+ * @mod_rate: module clock rate that needs to be set in order to have
+ *      a functional block.
  */
 struct sun8i_mixer_cfg {
         int             vi_num;
         int             ui_num;
         int             scaler_mask;
         int             ccsc;
+        unsigned long   mod_rate;
 };
 
 struct sun8i_mixer {