linux-kernel - Re: [PATCH v6 4/5] clk: aspeed: Register gated clocks

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Date:   Thu, 21 Dec 2017 15:39:27 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Joel Stanley <joel@....id.au>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Andrew Jeffery <andrew@...id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Jeremy Kerr <jk@...abs.org>,
        Rick Altherr <raltherr@...gle.com>,
        Ryan Chen <ryan_chen@...eedtech.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v6 4/5] clk: aspeed: Register gated clocks

On 11/28, Joel Stanley wrote:
> diff --git a/drivers/clk/clk-aspeed.c b/drivers/clk/clk-aspeed.c
> index 839243691b26..b5dc3e298693 100644
> --- a/drivers/clk/clk-aspeed.c
> +++ b/drivers/clk/clk-aspeed.c
> @@ -202,6 +202,107 @@ static const struct aspeed_clk_soc_data ast2400_data = {
>  	.calc_pll = aspeed_ast2400_calc_pll,
>  };
>  
> +static int aspeed_clk_enable(struct clk_hw *hw)
> +{
> +	struct aspeed_clk_gate *gate = to_aspeed_clk_gate(hw);
> +	unsigned long flags;
> +	u32 clk = BIT(gate->clock_idx);
> +	u32 rst = BIT(gate->reset_idx);
> +
> +	spin_lock_irqsave(gate->lock, flags);
> +
> +	if (gate->reset_idx >= 0) {
> +		/* Put IP in reset */
> +		regmap_update_bits(gate->map, ASPEED_RESET_CTRL, rst, rst);
> +
> +		/* Delay 100us */
> +		udelay(100);
> +	}
> +
> +	/* Enable clock */
> +	regmap_update_bits(gate->map, ASPEED_CLK_STOP_CTRL, clk, 0);
> +
> +	if (gate->reset_idx >= 0) {
> +		/* Delay 10ms */
> +		/* TODO: can we sleep here? */
> +		msleep(10);

No you can't sleep here. It needs to delay because this is inside
spinlock_irqsave.

> +
> +		/* Take IP out of reset */
> +		regmap_update_bits(gate->map, ASPEED_RESET_CTRL, rst, 0);
> +	}
> +
> +	spin_unlock_irqrestore(gate->lock, flags);
> +
> +	return 0;
> +}

-- 
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