linux-kernel - Re: [PATCH] clk: mediatek: Don't check HW status for mt8192/5's imp_iic

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Date:   Tue, 12 Jul 2022 18:44:24 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>
Cc:     Stephen Boyd <sboyd@...nel.org>, kernel@...labora.com,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Chun-Jie Chen <chun-jie.chen@...iatek.com>,
        Ikjoon Jang <ikjn@...omium.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Michael Turquette <mturquette@...libre.com>,
        Miles Chen <miles.chen@...iatek.com>,
        Ran Jianping <ran.jianping@....com.cn>,
        Weiyi Lu <weiyi.lu@...iatek.com>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] clk: mediatek: Don't check HW status for mt8192/5's
 imp_iic_wrap clocks

Hi,

On Tue, Jul 12, 2022 at 4:57 AM Nícolas F. R. A. Prado
<nfraprado@...labora.com> wrote:
>
> The imp_iic_wrap clocks on mt8192/mt8195 require that the i2c_sel parent
> clock be enabled before their hardware status can be checked. Since this
> wasn't taken into account, reading from the clk_summary debugfs file
> would cause the system to completely freeze.
>
> Assuming that this clock is managed only by the kernel, and not by any
> firmware, simply drop the is_enabled() optional callback and instead
> rely on the enable count for the imp_iic_wrap clocks.

That's the wrong way to go about it.

The I2C clocks already have the CLK_OPS_PARENT_ENABLE flag set. So the
issue is that somewhere in the clk core, a piece of code is not honoring
that flag.

And it seems that's in more than one place.

Regards
ChenYu

> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
>
> ---
>
>  drivers/clk/mediatek/clk-gate.c                | 6 ++++++
>  drivers/clk/mediatek/clk-gate.h                | 1 +
>  drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c | 2 +-
>  drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c | 2 +-
>  4 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clk/mediatek/clk-gate.c b/drivers/clk/mediatek/clk-gate.c
> index 421806236228..8e7c719a69b3 100644
> --- a/drivers/clk/mediatek/clk-gate.c
> +++ b/drivers/clk/mediatek/clk-gate.c
> @@ -124,6 +124,12 @@ static void mtk_cg_disable_inv_no_setclr(struct clk_hw *hw)
>         mtk_cg_clr_bit_no_setclr(hw);
>  }
>
> +const struct clk_ops mtk_clk_gate_ops_setclr_counted = {
> +       .enable         = mtk_cg_enable,
> +       .disable        = mtk_cg_disable,
> +};
> +EXPORT_SYMBOL_GPL(mtk_clk_gate_ops_setclr_counted);
> +
>  const struct clk_ops mtk_clk_gate_ops_setclr = {
>         .is_enabled     = mtk_cg_bit_is_cleared,
>         .enable         = mtk_cg_enable,
> diff --git a/drivers/clk/mediatek/clk-gate.h b/drivers/clk/mediatek/clk-gate.h
> index d9897ef53528..b5502b2911f5 100644
> --- a/drivers/clk/mediatek/clk-gate.h
> +++ b/drivers/clk/mediatek/clk-gate.h
> @@ -19,6 +19,7 @@ extern const struct clk_ops mtk_clk_gate_ops_setclr;
>  extern const struct clk_ops mtk_clk_gate_ops_setclr_inv;
>  extern const struct clk_ops mtk_clk_gate_ops_no_setclr;
>  extern const struct clk_ops mtk_clk_gate_ops_no_setclr_inv;
> +extern const struct clk_ops mtk_clk_gate_ops_setclr_counted;
>
>  struct mtk_gate_regs {
>         u32 sta_ofs;
> diff --git a/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c b/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c
> index 700356ac6a58..900ee601169c 100644
> --- a/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c
> +++ b/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c
> @@ -20,7 +20,7 @@ static const struct mtk_gate_regs imp_iic_wrap_cg_regs = {
>
>  #define GATE_IMP_IIC_WRAP(_id, _name, _parent, _shift)                 \
>         GATE_MTK_FLAGS(_id, _name, _parent, &imp_iic_wrap_cg_regs, _shift,      \
> -               &mtk_clk_gate_ops_setclr, CLK_OPS_PARENT_ENABLE)
> +               &mtk_clk_gate_ops_setclr_counted, CLK_OPS_PARENT_ENABLE)
>
>  static const struct mtk_gate imp_iic_wrap_c_clks[] = {
>         GATE_IMP_IIC_WRAP(CLK_IMP_IIC_WRAP_C_I2C10, "imp_iic_wrap_c_i2c10", "infra_i2c0", 0),
> diff --git a/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c b/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c
> index fbc809d05072..e50a77b844f4 100644
> --- a/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c
> +++ b/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c
> @@ -18,7 +18,7 @@ static const struct mtk_gate_regs imp_iic_wrap_cg_regs = {
>
>  #define GATE_IMP_IIC_WRAP(_id, _name, _parent, _shift)                         \
>         GATE_MTK_FLAGS(_id, _name, _parent, &imp_iic_wrap_cg_regs, _shift,      \
> -               &mtk_clk_gate_ops_setclr, CLK_OPS_PARENT_ENABLE)
> +               &mtk_clk_gate_ops_setclr_counted, CLK_OPS_PARENT_ENABLE)
>
>  static const struct mtk_gate imp_iic_wrap_s_clks[] = {
>         GATE_IMP_IIC_WRAP(CLK_IMP_IIC_WRAP_S_I2C5, "imp_iic_wrap_s_i2c5", "top_i2c", 0),
> --
> 2.37.0
>