linux-kernel - Re: [PATCH 4/4] clk: qcom: clk-krait: add apq/ipq8064 errata workaround

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Date:   Fri, 29 Apr 2022 18:00:45 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Ansuel Smith <ansuelsmth@...il.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Sricharan R <sricharan@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] clk: qcom: clk-krait: add apq/ipq8064 errata
 workaround

On 29/04/2022 15:01, Ansuel Smith wrote:
> Add apq/ipq8064 errata workaround where the sec_src clock gating needs to
> be disabled during switching. To enable this set disable_sec_src_gating
> in the mux struct.
> 
> Signed-off-by: Ansuel Smith <ansuelsmth@...il.com>
> ---
>   drivers/clk/qcom/clk-krait.c | 16 ++++++++++++++++
>   drivers/clk/qcom/clk-krait.h |  1 +
>   drivers/clk/qcom/krait-cc.c  |  1 +
>   3 files changed, 18 insertions(+)
> 
> diff --git a/drivers/clk/qcom/clk-krait.c b/drivers/clk/qcom/clk-krait.c
> index 6c367ad6506a..4a9b3296c45b 100644
> --- a/drivers/clk/qcom/clk-krait.c
> +++ b/drivers/clk/qcom/clk-krait.c
> @@ -18,13 +18,23 @@
>   static DEFINE_SPINLOCK(krait_clock_reg_lock);
>   
>   #define LPL_SHIFT	8
> +#define SECCLKAGD	BIT(4)
> +
>   static void __krait_mux_set_sel(struct krait_mux_clk *mux, int sel)
>   {
>   	unsigned long flags;
>   	u32 regval;
>   
>   	spin_lock_irqsave(&krait_clock_reg_lock, flags);
> +
>   	regval = krait_get_l2_indirect_reg(mux->offset);
> +
> +	/* apq/ipq8064 Errata: disable sec_src clock gating during switch. */
> +	if (mux->disable_sec_src_gating) {
> +		regval |= SECCLKAGD;
> +		krait_set_l2_indirect_reg(mux->offset, regval);
> +	}
> +
>   	regval &= ~(mux->mask << mux->shift);
>   	regval |= (sel & mux->mask) << mux->shift;
>   	if (mux->lpl) {
> @@ -33,6 +43,12 @@ static void __krait_mux_set_sel(struct krait_mux_clk *mux, int sel)
>   	}
>   	krait_set_l2_indirect_reg(mux->offset, regval);
>   
> +	/* apq/ipq8064 Errata: re-enabled sec_src clock gating. */
> +	if (mux->disable_sec_src_gating) {
> +		regval &= ~SECCLKAGD;
> +		krait_set_l2_indirect_reg(mux->offset, regval);
> +	}
> +
>   	/* Wait for switch to complete. */
>   	mb();
>   	udelay(1);
> diff --git a/drivers/clk/qcom/clk-krait.h b/drivers/clk/qcom/clk-krait.h
> index 9120bd2f5297..f930538c539e 100644
> --- a/drivers/clk/qcom/clk-krait.h
> +++ b/drivers/clk/qcom/clk-krait.h
> @@ -15,6 +15,7 @@ struct krait_mux_clk {
>   	u8		safe_sel;
>   	u8		old_index;
>   	bool		reparent;
> +	bool		disable_sec_src_gating;
>   
>   	struct clk_hw	hw;
>   	struct notifier_block   clk_nb;
> diff --git a/drivers/clk/qcom/krait-cc.c b/drivers/clk/qcom/krait-cc.c
> index 4d4b657d33c3..0f88bf41ec6e 100644
> --- a/drivers/clk/qcom/krait-cc.c
> +++ b/drivers/clk/qcom/krait-cc.c
> @@ -138,6 +138,7 @@ krait_add_sec_mux(struct device *dev, int id, const char *s,
>   	mux->parent_map = sec_mux_map;
>   	mux->hw.init = &init;
>   	mux->safe_sel = 0;
> +	mux->disable_sec_src_gating = true;

This has to be guarded with the of_compatible checks. Otherwise you'd 
apply this errata to all Krait CPUs, not only apq/ipq8064.

At least this should be limited to krait-cc-v1 with the note that there 
is no way to distinguish between platforms.

>   
>   	init.name = kasprintf(GFP_KERNEL, "krait%s_sec_mux", s);
>   	if (!init.name)


-- 
With best wishes
Dmitry