linux-kernel - Re: [PATCH 1/4] clk: meson: meson8b: Fix the first parent of vid_pll_in

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Date:   Thu, 16 Apr 2020 12:32:21 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org, linux-clk@...r.kernel.org
Cc:     narmstrong@...libre.com, mturquette@...libre.com, sboyd@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] clk: meson: meson8b: Fix the first parent of vid_pll_in_sel


On Tue 14 Apr 2020 at 22:00, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:

> Use hdmi_pll_lvds_out as parent of the vid_pll_in_sel clock. It's not
> easy to see that the vendor kernel does the same, but it actually does.
> meson_clk_pll_ops in mainline still cannot fully recalculate all rates
> from the HDMI PLL registers because some register bits (at the time of
> writing it's unknown which bits are used for this) double the HDMI PLL
> output rate (compared to simply considering M, N and FRAC).

Have you considered adding a fixed_factor pre-multiplier, like in the
gxbb driver ?

Seems to be the same thing

>
> Update the vid_pll_in_sel parent so our clock calculation works for
> simple clock settings like the CVBS output (where no rate doubling is
> going on). The PLL ops need to be fixed later on for more complex clock
> settings (all HDMI rates).
>
> Fixes: 6cb57c678bb70 ("clk: meson: meson8b: add the read-only video clock trees")
> Suggested-by: Neil Armstrong <narmstrong@...libre.com>
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
>  drivers/clk/meson/meson8b.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
> index 7c55c695cbae..90d284ffc780 100644
> --- a/drivers/clk/meson/meson8b.c
> +++ b/drivers/clk/meson/meson8b.c
> @@ -1077,7 +1077,7 @@ static struct clk_regmap meson8b_vid_pll_in_sel = {
>  		 * Meson8m2: vid2_pll
>  		 */
>  		.parent_hws = (const struct clk_hw *[]) {
> -			&meson8b_hdmi_pll_dco.hw
> +			&meson8b_hdmi_pll_lvds_out.hw
>  		},
>  		.num_parents = 1,
>  		.flags = CLK_SET_RATE_PARENT,