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>
---
 drivers/clk/mediatek/clk-mt8188-topckgen.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/mediatek/clk-mt8188-topckgen.c b/drivers/clk/mediatek/clk-mt8188-topckgen.c
index 2ccc8a1c98f9..74ee692ac613 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"
 };
 
 static const char * const camtg_parents[] = {
-- 
2.45.2

Il 20/09/24 15:41, Pablo Sun ha scritto:
> 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>

Hi,

> 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>
> ---
>    drivers/clk/mediatek/clk-mt8188-topckgen.c | 7 +++++--
>    1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/mediatek/clk-mt8188-topckgen.c b/drivers/clk/mediatek/clk-mt8188-topckgen.c
> index 2ccc8a1c98f9..74ee692ac613 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",
nit: Comma at the end of mainpll_d5_d2 is unnecessary.
> -	"univpll_d6",
> -	"univpll_d7"
>    };
>    
>    static const char * const camtg_parents[] = {
> -- 
> 2.45.2
> 
>