Re: [PATCH 4/9] clk: imx: add pllv4 support

From: Dong Aisheng <dongas86@gmail.com>
To: Stephen Boyd <sboyd@codeaurora.org>
Cc: Dong Aisheng <aisheng.dong@nxp.com>,
	linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, mturquette@baylibre.com,
	shawnguo@kernel.org, Anson.Huang@nxp.com, ping.bai@nxp.com
Subject: Re: [PATCH 4/9] clk: imx: add pllv4 support
Date: Tue, 20 Jun 2017 17:31:43 +0800	[thread overview]
Message-ID: <20170620093143.GD6805@b29396-OptiPlex-7040> (raw)
In-Reply-To: <20170620015917.GO4493@codeaurora.org>

On Mon, Jun 19, 2017 at 06:59:17PM -0700, Stephen Boyd wrote:
> On 05/15, Dong Aisheng wrote:
> >  obj-$(CONFIG_SOC_IMX1)   += clk-imx1.o
> > diff --git a/drivers/clk/imx/clk-pllv4.c b/drivers/clk/imx/clk-pllv4.c
> > new file mode 100644
> > index 0000000..502da64
> > --- /dev/null
> > +++ b/drivers/clk/imx/clk-pllv4.c
> > @@ -0,0 +1,196 @@
> > +/*
> > + * Copyright (C) 2016 Freescale Semiconductor, Inc.
> > + * Copyright 2017 NXP
> > + *
> > + * Author: Dong Aisheng <aisheng.dong@nxp.com>
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; either version 2
> > + * of the License, or (at your option) any later version.
> > + *
> > + * http://www.opensource.org/licenses/gpl-license.html
> > + * http://www.gnu.org/copyleft/gpl.html
> > + */
> > +
> > +#include <linux/clk-provider.h>
> > +#include <linux/clk.h>
> 
> Is this include used?
> 

Nice catch. Will remove.

> > +#include <linux/delay.h>
> > +#include <linux/err.h>
> > +#include <linux/slab.h>
> > +
> > +/* PLL Control Status Register (xPLLCSR) */
> > +#define PLL_CSR_OFFSET		0x0
> > +#define PLL_VLD			BIT(24)
> > +#define PLL_EN			BIT(0)
> > +
> > +/* PLL Configuration Register (xPLLCFG) */
> > +#define PLL_CFG_OFFSET		0x08
> > +#define BP_PLL_MULT		16
> > +#define BM_PLL_MULT		(0x7f << 16)
> > +
> > +/* PLL Numerator Register (xPLLNUM) */
> > +#define PLL_NUM_OFFSET		0x10
> > +
> > +/* PLL Denominator Register (xPLLDENOM) */
> > +#define PLL_DENOM_OFFSET	0x14
> > +
> > +struct clk_pllv4 {
> > +	struct clk_hw	hw;
> > +	void __iomem	*base;
> > +};
> > +
> > +/* Valid PLL MULT Table */
> > +static const int pllv4_mult_table[] = {33, 27, 22, 20, 17, 16};
> > +
> > +#define to_clk_pllv4(__hw) container_of(__hw, struct clk_pllv4, hw)
> > +
> > +static int clk_pllv4_wait_lock(struct clk_pllv4 *pll)
> > +{
> > +	unsigned long timeout = jiffies + msecs_to_jiffies(5);
> > +
> > +	/* Wait for PLL to lock */
> > +	do {
> > +		if (readl_relaxed(pll->base  + PLL_CSR_OFFSET) & PLL_VLD)
> > +			break;
> > +		if (time_after(jiffies, timeout))
> > +			break;
> > +			usleep_range(50, 500);
> > +	} while (1);
> > +
> > +	return readl_relaxed(pll->base + PLL_CSR_OFFSET) & PLL_VLD ?
> > +	       0 : -ETIMEDOUT;
> 
> Use readl_poll_timeout() instead?
> 

Good idea.

> > +}
> > +
> > +static int clk_pllv4_is_enabled(struct clk_hw *hw)
> > +{
> > +	struct clk_pllv4 *pll = to_clk_pllv4(hw);
> > +
> > +	if (readl_relaxed(pll->base) & PLL_EN)
> > +		return 1;
> > +
> > +	return 0;
> > +}
> > +
> > +static unsigned long clk_pllv4_recalc_rate(struct clk_hw *hw,
> > +					   unsigned long parent_rate)
> > +{
> > +	struct clk_pllv4 *pll = to_clk_pllv4(hw);
> > +	u32 div;
> > +
> > +	div = (readl_relaxed(pll->base + PLL_CFG_OFFSET)
> > +	       & BM_PLL_MULT) >> BP_PLL_MULT;
> 
> Put that on multiple lines please:
> 
> 	div = readl_relaxed(pll->base + PLL_CFG_OFFSET);
> 	div &= BM_PLL_MULT;
> 	div >>= BP_PLL_MULT; /* Why BP this time? */
> 

Of course.

> > +
> > +	return parent_rate * div;
> > +}
> > +
> > +static long clk_pllv4_round_rate(struct clk_hw *hw, unsigned long rate,
> > +				 unsigned long *prate)
> > +{
> > +	unsigned long parent_rate = *prate;
> > +	unsigned long round_rate, i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(pllv4_mult_table); i++) {
> > +		round_rate = parent_rate * pllv4_mult_table[i];
> > +		if (rate >= round_rate)
> > +			return round_rate;
> > +	}
> > +
> > +	return round_rate;
> > +}
> > +
> > +static bool clk_pllv4_is_valid_mult(unsigned int mult)
> > +{
> > +	int i;
> > +
> > +	/* check if mult is in valid MULT table */
> > +	for (i = 0; i < ARRAY_SIZE(pllv4_mult_table); i++) {
> > +		if (pllv4_mult_table[i] == mult)
> > +			return true;
> > +	}
> > +
> > +	return false;
> > +}
> > +
> > +static int clk_pllv4_set_rate(struct clk_hw *hw, unsigned long rate,
> > +			      unsigned long parent_rate)
> > +{
> > +	struct clk_pllv4 *pll = to_clk_pllv4(hw);
> > +	u32 val, mult;
> > +
> > +	if (clk_pllv4_is_enabled(hw)) {
> > +		WARN(1, "clk_pllv4: can't change rate when pll is enabled");
> > +		return -EINVAL;
> 
> Sad, CLK_SET_RATE_GATE isn't working for you I suppose?
> 

CLK_SET_RATE_GATE can't work in early stage before running clk_disable_unused.
At that point, the clock tree state is still not consistent with HW.
e.g. prepare/enable count is still zero but it's actually enabled due to
reset state or bootloader.

The code here is adding a double check in case user sets rate in early stage.

However, probably it could also be moved into clock core as it's not platform
dependant behavior?

Regards
Dong Aisheng

> > +	}
> > +
> > +	mult = rate / parent_rate;
> > +
> > +	if (clk_pllv4_is_valid_mult(mult))
> > +		return -EINVAL;
> > +
> > +	val = readl_relaxed(pll->base + PLL_CFG_OFFSET);
> > +	val &= ~BM_PLL_MULT;
> > +	val |= mult << BP_PLL_MULT;
> > +	writel_relaxed(val, pll->base + PLL_CFG_OFFSET);
> > +
> > +	return 0;
> > +}
> > +
> 
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