clk: mediatek: clk-mt8188-topckgen: Remove univpll from parents of mfg_core_tmp

Same as MT8195, MT8188 GPU clock is primarly supplied by the dedicated
mfgpll. The clock "mfg_core_tmp" is only used as an alt clock when
setting mfgpll clock rate.

If we keep the univpll parents from mfg_core_tmp, when setting
GPU frequency to 390000000, the common clock framework would switch
the parent to univpll, instead of setting mfgpll to 390000000:

    mfgpll                            0        0        0   949999756
    univpll                           2        2        0  2340000000
       univpll_d6                     1        1        0   390000000
          top_mfg_core_tmp            1        1        0   390000000
             mfg_ck_fast_ref          1        1        0   390000000
                mfgcfg_bg3d           1        1        0   390000000

This results in failures when subsequent devfreq operations need to
switch to other frequencies. So remove univpll from the parent list.

This solution is taken from commit 72d38ed720e9 ("clk: mediatek:
clk-mt8195-topckgen: Drop univplls from mfg mux parents")

Signed-off-by: Pablo Sun <pablo.sun@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20240927103005.17605-3-pablo.sun@mediatek.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/clk/mediatek/clk-mt8188-topckgen.c b/drivers/clk/mediatek/clk-mt8188-topckgen.c
index c4baf4076ed6..6b07abe9a8f5 100644
--- a/drivers/clk/mediatek/clk-mt8188-topckgen.c
+++ b/drivers/clk/mediatek/clk-mt8188-topckgen.c
@@ -342,11 +342,14 @@ static const char * const dsp7_parents[] = {
 	"univpll_d3"
 };
 
+/*
+ * MFG can be also parented to "univpll_d6" and "univpll_d7":
+ * these have been removed from the parents list to let us
+ * achieve GPU DVFS without any special clock handlers.
+ */
 static const char * const mfg_core_tmp_parents[] = {
 	"clk26m",
-	"mainpll_d5_d2",
-	"univpll_d6",
-	"univpll_d7"
+	"mainpll_d5_d2"
 };
 
 static const char * const camtg_parents[] = {