linux-kernel - Re: [PATCH v2 2/2] clk: mediatek: mt8195-topckgen: Refactor parents for top

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Message-ID: <CAGXv+5EoVnfCLfJ+6t8FiwuJq-eyZQZNh9H+7TD+yGkEWFO3pw@mail.gmail.com>
Date:   Mon, 23 Oct 2023 15:00:09 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     sboyd@...nel.org, mturquette@...libre.com, matthias.bgg@...il.com,
        msp@...libre.com, amergnat@...libre.com, yangyingliang@...wei.com,
        u.kleine-koenig@...gutronix.de, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v2 2/2] clk: mediatek: mt8195-topckgen: Refactor parents
 for top_dp/edp muxes

On Wed, Oct 18, 2023 at 6:35 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> The top_dp and top_edp muxes can be both parented to either TVDPLL1
> or TVDPLL2, two identically specced PLLs for the specific purpose of
> giving out pixel clock: this becomes a problem when the MediaTek
> DisplayPort Interface (DPI) driver tries to set the pixel clock rate.
>
> In the usecase of two simultaneous outputs (using two controllers),
> it was seen that one of the displays would sometimes display garbled
> output (if any at all) and this was because:
>  - top_edp was set to TVDPLL1, outputting X GHz
>  - top_dp was set to TVDPLL2, outputting Y GHz
>    - mtk_dpi calls clk_set_rate(top_edp, Z GHz)
>      - top_dp is switched to TVDPLL1
>      - TVDPLL1 changes its rate, top_edp outputs the wrong rate.
>      - eDP display is garbled
>
> To solve this issue, remove all TVDPLL1 parents from `top_dp` and
> all TVDPLL2 parents from `top_edp`, plus, necessarily switch both
> clocks to use the new MUX_GATE_CLR_SET_UPD_INDEXED() macro to be
> able to use the right bit index for the new parents list.
>
> Reviewed-by: Alexandre Mergnat <amergnat@...libre.com>
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
>  drivers/clk/mediatek/clk-mt8195-topckgen.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/clk/mediatek/clk-mt8195-topckgen.c b/drivers/clk/mediatek/clk-mt8195-topckgen.c
> index 5c426a1c94c7..4529255376e9 100644
> --- a/drivers/clk/mediatek/clk-mt8195-topckgen.c
> +++ b/drivers/clk/mediatek/clk-mt8195-topckgen.c
> @@ -417,15 +417,21 @@ static const char * const pwrmcu_parents[] = {


Nit: I'd add a comment saying this list isn't the full list for reasons.

Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>

>  static const char * const dp_parents[] = {
>         "clk26m",
> -       "tvdpll1_d2",
>         "tvdpll2_d2",
> -       "tvdpll1_d4",
>         "tvdpll2_d4",
> -       "tvdpll1_d8",
>         "tvdpll2_d8",
> -       "tvdpll1_d16",
>         "tvdpll2_d16"
>  };
> +static const u8 dp_parents_idx[] = { 0, 2, 4, 6, 8 };
> +
> +static const char * const edp_parents[] = {
> +       "clk26m",
> +       "tvdpll1_d2",
> +       "tvdpll1_d4",
> +       "tvdpll1_d8",
> +       "tvdpll1_d16"
> +};
> +static const u8 edp_parents_idx[] = { 0, 1, 3, 5, 7 };
>
>  static const char * const disp_pwm_parents[] = {
>         "clk26m",
> @@ -957,11 +963,11 @@ static const struct mtk_mux top_mtk_muxes[] = {
>         MUX_GATE_CLR_SET_UPD_FLAGS(CLK_TOP_PWRMCU, "top_pwrmcu",
>                 pwrmcu_parents, 0x08C, 0x090, 0x094, 16, 3, 23, 0x08, 6,
>                 CLK_IS_CRITICAL | CLK_SET_RATE_PARENT),
> -       MUX_GATE_CLR_SET_UPD(CLK_TOP_DP, "top_dp",
> -               dp_parents, 0x08C, 0x090, 0x094, 24, 4, 31, 0x08, 7),
> +       MUX_GATE_CLR_SET_UPD_INDEXED(CLK_TOP_DP, "top_dp",
> +               dp_parents, dp_parents_idx, 0x08C, 0x090, 0x094, 24, 4, 31, 0x08, 7),
>         /* CLK_CFG_10 */
> -       MUX_GATE_CLR_SET_UPD(CLK_TOP_EDP, "top_edp",
> -               dp_parents, 0x098, 0x09C, 0x0A0, 0, 4, 7, 0x08, 8),
> +       MUX_GATE_CLR_SET_UPD_INDEXED(CLK_TOP_EDP, "top_edp",
> +               edp_parents, edp_parents_idx, 0x098, 0x09C, 0x0A0, 0, 4, 7, 0x08, 8),
>         MUX_GATE_CLR_SET_UPD(CLK_TOP_DPI, "top_dpi",
>                 dp_parents, 0x098, 0x09C, 0x0A0, 8, 4, 15, 0x08, 9),
>         MUX_GATE_CLR_SET_UPD(CLK_TOP_DISP_PWM0, "top_disp_pwm0",
> --
> 2.42.0
>