linux-kernel - Re: [PATCH] clk: meson: meson8b: Don't rely on u-boot to init all GP

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Message-ID: <1jees3i4r5.fsf@starbuckisacylon.baylibre.com>
Date:   Sat, 02 May 2020 02:01:50 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org
Cc:     narmstrong@...libre.com, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: meson: meson8b: Don't rely on u-boot to init all GP_PLL registers


On Fri 01 May 2020 at 23:57, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:

> Not all u-boot versions initialize the HHI_GP_PLL_CNTL[2-5] registers.
> In that case all HHI_GPLL_PLL_CNTL[1-5] registers are 0x0 and when
> booting Linux the PLL fails to lock.
> The initialization sequence from u-boot is:
> - put the PLL into reset
> - write 0x59C88000 to HHI_GP_PLL_CNTL2
> - write 0xCA463823 to HHI_GP_PLL_CNTL3
> - write 0x0286A027 to HHI_GP_PLL_CNTL4
> - write 0x00003000 to HHI_GP_PLL_CNTL5
> - set M, N, OD and the enable bit
> - take the PLL out of reset
> - check if it has locked
> - disable the PLL
>
> In Linux we already initialize M, N, OD, the enable and the reset bits.
> Also the HHI_GP_PLL_CNTL[2-5] registers with these magic values (the
> exact meaning is unknown) so the PLL can lock when the vendor u-boot did
> not initialize these registers yet.
>
> Fixes: b882964b376f21 ("clk: meson: meson8b: add support for the GP_PLL clock on Meson8m2")
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
> Jerome, this one is also not critical because we don't enable the VPU
> yet. So I based this on commit 16afd70af5b21b ("clk: meson: meson8b:
> Make the CCF use the glitch-free VPU mux").
>
>
>  drivers/clk/meson/meson8b.c | 9 +++++++++
>  drivers/clk/meson/meson8b.h | 4 ++++
>  2 files changed, 13 insertions(+)

Applied, Thx

>
> diff --git a/drivers/clk/meson/meson8b.c b/drivers/clk/meson/meson8b.c
> index 811af1c11456..edc09d050ecf 100644
> --- a/drivers/clk/meson/meson8b.c
> +++ b/drivers/clk/meson/meson8b.c
> @@ -1918,6 +1918,13 @@ static struct clk_regmap meson8b_mali = {
>  	},
>  };
>  
> +static const struct reg_sequence meson8m2_gp_pll_init_regs[] = {
> +	{ .reg = HHI_GP_PLL_CNTL2,	.def = 0x59c88000 },
> +	{ .reg = HHI_GP_PLL_CNTL3,	.def = 0xca463823 },
> +	{ .reg = HHI_GP_PLL_CNTL4,	.def = 0x0286a027 },
> +	{ .reg = HHI_GP_PLL_CNTL5,	.def = 0x00003000 },
> +};
> +
>  static const struct pll_params_table meson8m2_gp_pll_params_table[] = {
>  	PLL_PARAMS(182, 3),
>  	{ /* sentinel */ },
> @@ -1951,6 +1958,8 @@ static struct clk_regmap meson8m2_gp_pll_dco = {
>  			.width   = 1,
>  		},
>  		.table = meson8m2_gp_pll_params_table,
> +		.init_regs = meson8m2_gp_pll_init_regs,
> +		.init_count = ARRAY_SIZE(meson8m2_gp_pll_init_regs),
>  	},
>  	.hw.init = &(struct clk_init_data){
>  		.name = "gp_pll_dco",
> diff --git a/drivers/clk/meson/meson8b.h b/drivers/clk/meson/meson8b.h
> index 94ce3ef0c1d5..cd38ae2a9cb5 100644
> --- a/drivers/clk/meson/meson8b.h
> +++ b/drivers/clk/meson/meson8b.h
> @@ -20,6 +20,10 @@
>   * [0] http://dn.odroid.com/S805/Datasheet/S805_Datasheet%20V0.8%2020150126.pdf
>   */
>  #define HHI_GP_PLL_CNTL			0x40  /* 0x10 offset in data sheet */
> +#define HHI_GP_PLL_CNTL2		0x44  /* 0x11 offset in data sheet */
> +#define HHI_GP_PLL_CNTL3		0x48  /* 0x12 offset in data sheet */
> +#define HHI_GP_PLL_CNTL4		0x4C  /* 0x13 offset in data sheet */
> +#define HHI_GP_PLL_CNTL5		0x50  /* 0x14 offset in data sheet */
>  #define HHI_VIID_CLK_DIV		0x128 /* 0x4a offset in data sheet */
>  #define HHI_VIID_CLK_CNTL		0x12c /* 0x4b offset in data sheet */
>  #define HHI_GCLK_MPEG0			0x140 /* 0x50 offset in data sheet */