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Date:   Thu, 05 Oct 2017 18:07:52 +1030
From:   Andrew Jeffery <andrew@...id.au>
To:     Joel Stanley <joel@....id.au>, Lee Jones <lee.jones@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        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 v4 4/5] clk: aspeed: Register gated clocks

On Tue, 2017-10-03 at 17:25 +1030, Joel Stanley wrote:
> The majority of the clocks in the system are gates paired with a reset
> controller that holds the IP in reset.
> 
> This borrows from clk_hw_register_gate, but registers two 'gates', one
> to control the clock enable register and the other to control the reset
> IP. This allows us to enforce the ordering:
> 
>  1. Place IP in reset
>  2. Enable clock
>  3. Delay
>  4. Release reset
> 
> There are some gates that do not have an associated reset; these are
> handled by using -1 as the index for the reset.
> 
> Signed-off-by: Joel Stanley <joel@....id.au>
> 
> ---
> v4:
>  - Drop useless 'disable clock' comment
>  - Drop CLK_IS_BASIC flag
>  - Fix 'there are a number of clocks...' comment
>  - Pass device to clk registration functions
>  - Check for errors when registering clk_hws
> v3:
>  - Remove gates offset as gates are now at the start of the list
> ---
>  drivers/clk/clk-aspeed.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 130 insertions(+)
> 
> diff --git a/drivers/clk/clk-aspeed.c b/drivers/clk/clk-aspeed.c
> index adb295292189..a424b056e767 100644
> --- a/drivers/clk/clk-aspeed.c
> +++ b/drivers/clk/clk-aspeed.c
> @@ -228,6 +228,107 @@ 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);
> +
> +		/* Take IP out of reset */
> +		regmap_update_bits(gate->map, ASPEED_RESET_CTRL, rst, 0);
> +	}
> +
> +	spin_unlock_irqrestore(gate->lock, flags);
> +
> +	return 0;
> +}
> +
> +static void aspeed_clk_disable(struct clk_hw *hw)
> +{
> +	struct aspeed_clk_gate *gate = to_aspeed_clk_gate(hw);
> +	unsigned long flags;
> +	u32 clk = BIT(gate->clock_idx);
> +
> +	spin_lock_irqsave(gate->lock, flags);
> +
> +	regmap_update_bits(gate->map, ASPEED_CLK_STOP_CTRL, clk, clk);
> +
> +	spin_unlock_irqrestore(gate->lock, flags);
> +}
> +
> +static int aspeed_clk_is_enabled(struct clk_hw *hw)
> +{
> +	struct aspeed_clk_gate *gate = to_aspeed_clk_gate(hw);
> +	u32 clk = BIT(gate->clock_idx);
> +	u32 reg;
> +
> +	regmap_read(gate->map, ASPEED_CLK_STOP_CTRL, &reg);
> +
> +	return (reg & clk) ? 0 : 1;

Kill a branch, save the internet: return !(reg & clk);

But regardless, the patch seems sensible to me modulo the power domain
discussion. However as it's more clk-y than Aspeed-y I don't feel entirely
qualified to provide a r-b, so instead:

Acked-by: Andrew Jeffery <andrew@...id.au>

> +}
> +
> +static const struct clk_ops aspeed_clk_gate_ops = {
> +	.enable = aspeed_clk_enable,
> +	.disable = aspeed_clk_disable,
> +	.is_enabled = aspeed_clk_is_enabled,
> +};
> +
> +static struct clk_hw *aspeed_clk_hw_register_gate(struct device *dev,
> +		const char *name, const char *parent_name, unsigned long flags,
> +		struct regmap *map, u8 clock_idx, u8 reset_idx,
> +		u8 clk_gate_flags, spinlock_t *lock)
> +{
> +	struct aspeed_clk_gate *gate;
> +	struct clk_init_data init;
> +	struct clk_hw *hw;
> +	int ret;
> +
> +	gate = kzalloc(sizeof(*gate), GFP_KERNEL);
> +	if (!gate)
> +		return ERR_PTR(-ENOMEM);
> +
> +	init.name = name;
> +	init.ops = &aspeed_clk_gate_ops;
> +	init.flags = flags;
> +	init.parent_names = parent_name ? &parent_name : NULL;
> +	init.num_parents = parent_name ? 1 : 0;
> +
> +	gate->map = map;
> +	gate->clock_idx = clock_idx;
> +	gate->reset_idx = reset_idx;
> +	gate->flags = clk_gate_flags;
> +	gate->lock = lock;
> +	gate->hw.init = &init;
> +
> +	hw = &gate->hw;
> +	ret = clk_hw_register(dev, hw);
> +	if (ret) {
> +		kfree(gate);
> +		hw = ERR_PTR(ret);
> +	}
> +
> +	return hw;
> +}
> +
>  static int aspeed_clk_probe(struct platform_device *pdev)
>  {
>  	const struct aspeed_clk_soc_data *soc_data;
> @@ -235,6 +336,7 @@ static int aspeed_clk_probe(struct platform_device *pdev)
>  	struct regmap *map;
>  	struct clk_hw *hw;
>  	u32 val, rate;
> +	int i;
>  
>  	map = syscon_node_to_regmap(dev->of_node);
>  	if (IS_ERR(map)) {
> @@ -323,6 +425,34 @@ static int aspeed_clk_probe(struct platform_device *pdev)
>  		return PTR_ERR(hw);
>  	aspeed_clk_data->hws[ASPEED_CLK_BCLK] = hw;
>  
> +	/*
> +	 * TODO: There are a number of clocks that not included in this driver
> +	 * as more information is required:
> +	 *   D2-PLL
> +	 *   D-PLL
> +	 *   YCLK
> +	 *   RGMII
> +	 *   RMII
> +	 *   UART[1..5] clock source mux
> +	 */
> +
> +	for (i = 0; i < ARRAY_SIZE(aspeed_gates); i++) {
> +		const struct aspeed_gate_data *gd = &aspeed_gates[i];
> +
> +		hw = aspeed_clk_hw_register_gate(dev,
> +				gd->name,
> +				gd->parent_name,
> +				gd->flags,
> +				map,
> +				gd->clock_idx,
> +				gd->reset_idx,
> +				CLK_GATE_SET_TO_DISABLE,
> +				&aspeed_clk_lock);
> +		if (IS_ERR(hw))
> +			return PTR_ERR(hw);
> +		aspeed_clk_data->hws[i] = hw;
> +	}
> +
>  	return 0;
>  };
>  
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