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Message-ID: <DB3PR0402MB3916926286A5F4AE1B0E82A3F5390@DB3PR0402MB3916.eurprd04.prod.outlook.com>
Date: Mon, 29 Apr 2019 12:33:04 +0000
From: Anson Huang <anson.huang@....com>
To: Aisheng Dong <aisheng.dong@....com>,
"mturquette@...libre.com" <mturquette@...libre.com>,
"sboyd@...nel.org" <sboyd@...nel.org>,
"shawnguo@...nel.org" <shawnguo@...nel.org>,
"s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
"kernel@...gutronix.de" <kernel@...gutronix.de>,
"festevam@...il.com" <festevam@...il.com>,
"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH] clk: imx: add fractional-N pll support to pllv4
Hi, Aisheng
> -----Original Message-----
> From: Aisheng Dong
> Sent: Monday, April 29, 2019 7:36 PM
> To: Anson Huang <anson.huang@....com>; mturquette@...libre.com;
> sboyd@...nel.org; shawnguo@...nel.org; s.hauer@...gutronix.de;
> kernel@...gutronix.de; festevam@...il.com; linux-clk@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org
> Cc: dl-linux-imx <linux-imx@....com>
> Subject: RE: [PATCH] clk: imx: add fractional-N pll support to pllv4
>
> > From: Aisheng Dong
> > Sent: Monday, April 29, 2019 7:28 PM
> > Subject: RE: [PATCH] clk: imx: add fractional-N pll support to pllv4
> > > The pllv4 supports fractional-N function, the formula is:
> > >
> > > PLL output freq = input * (mult + num/denom),
> > >
> > > This patch adds fractional-N function support, including clock round
> > > rate, calculate rate and set rate, with this patch, the clock rate
> > > of APLL in clock tree is more accurate than before:
> > >
>
> BTW, one more question:
> Does B0 chip support fractional for SPLL as this patch affects both APLL and
> SPLL?
> I did not see NUM&DENOM register for SPLL in my doc, not sure if it's latest
> version.
There are NUM&DENOM for both SPLL and APLL in reference manual, my RM is
V2(2.0), published on 12/2017.
Anson.
>
> Regards
> Dong Aisheng
>
> > > Without fraction:
> > > apll_pre_sel 1 1 1 24000000
> > > 0 0 50000
> > > apll_pre_div 1 1 2 24000000
> > > 0 0 50000
> > > apll 1 1 2 528000000
> > > 0 0 50000
> > > apll_pfd3 0 0 0 792000000
> > > 0 0 50000
> > > apll_pfd2 0 0 0 339428571
> > > 0 0 50000
> > > apll_pfd1 0 0 0 352000000
> > > 0 0 50000
> > > usdhc0 0 0 0
> > 352000000
> > > 0 0 50000
> > > apll_pfd0 1 1 1 352000000
> > > 0 0 50000
> > >
> > > With fraction:
> > > apll_pre_sel 1 1 1 24000000
> > > 0 0 50000
> > > apll_pre_div 1 1 2 24000000
> > > 0 0 50000
> > > apll 1 1 2 529200000
> > > 0 0 50000
> > > apll_pfd3 0 0 0 793800000
> > > 0 0 50000
> > > apll_pfd2 0 0 0 340200000
> > > 0 0 50000
> > > apll_pfd1 0 0 0 352800000
> > > 0 0 50000
> > > usdhc0 0 0 0
> > 352800000
> > > 0 0 50000
> > > apll_pfd0 1 1 1 352800000
> > > 0 0 50000
> > >
> > > Signed-off-by: Anson Huang <Anson.Huang@....com>
> > > ---
> > > drivers/clk/imx/clk-pllv4.c | 68
> > > +++++++++++++++++++++++++++++++++++++++------
> > > 1 file changed, 60 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/clk/imx/clk-pllv4.c
> > > b/drivers/clk/imx/clk-pllv4.c index d38bc9f..4ced5ca 100644
> > > --- a/drivers/clk/imx/clk-pllv4.c
> > > +++ b/drivers/clk/imx/clk-pllv4.c
> > > @@ -64,13 +64,18 @@ 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;
> > > + u32 mult = readl_relaxed(pll->base + PLL_CFG_OFFSET);
> > > + u32 mfn = readl_relaxed(pll->base + PLL_NUM_OFFSET);
> > > + u32 mfd = readl_relaxed(pll->base + PLL_DENOM_OFFSET);
> >
> > Nitpick:
> > We usually don't write code like this.
> > How about separate the assignment from declaration?
> >
> > > + u64 temp64 = parent_rate;
> > >
> > > - div = readl_relaxed(pll->base + PLL_CFG_OFFSET);
> > > - div &= BM_PLL_MULT;
> > > - div >>= BP_PLL_MULT;
> > > + mult &= BM_PLL_MULT;
> > > + mult >>= BP_PLL_MULT;
> > >
> > > - return parent_rate * div;
> > > + temp64 *= mfn;
> > > + do_div(temp64, mfd);
> > > +
> > > + return (parent_rate * mult) + (u32)temp64;
> > > }
> > >
> > > static long clk_pllv4_round_rate(struct clk_hw *hw, unsigned long
> > > rate, @@
> > > -78,14 +83,47 @@ static long clk_pllv4_round_rate(struct clk_hw *hw,
> > > unsigned long rate, {
> > > unsigned long parent_rate = *prate;
> > > unsigned long round_rate, i;
> > > + bool found = false;
> > > + u32 mfn, mfd = 1000000;
> > > + u32 max_mfd = 0x3FFFFFFF;
> >
> > Please keep sort from long to short.
> > And the multi Max_mfd definitions could be move out the function and
> > Defined use macro.
> >
> > > + u64 temp64;
> > >
> > > 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;
> > > + if (rate >= round_rate) {
> > > + found = true;
> > > + break;
> > > + }
> > > + }
> > > +
> > > + if (!found) {
> > > + pr_warn("%s: unable to round rate %lu, parent rate %lu\n",
> > > + clk_hw_get_name(hw), rate, parent_rate);
> > > + return 0;
> > > }
> > >
> > > - return round_rate;
> > > + if (parent_rate <= max_mfd)
> > > + mfd = parent_rate;
> > > +
> > > + temp64 = (u64)(rate - round_rate);
> > > + temp64 *= mfd;
> > > + do_div(temp64, parent_rate);
> > > + mfn = temp64;
> > > +
> > > + /*
> > > + * NOTE: The value of numerator must always be configured to be
> > > + * less than the value of the denominator. If we can't get a proper
> > > + * pair of mfn/mfd, we simply return the round_rate without using
> > > + * the frac part.
> > > + */
> > > + if (mfn >= mfd)
> > > + return round_rate;
> > > +
> > > + temp64 = (u64)parent_rate;
> > > + temp64 *= mfn;
> > > + do_div(temp64, mfd);
> > > +
> > > + return round_rate + (u32)temp64;
> > > }
> > >
> > > static bool clk_pllv4_is_valid_mult(unsigned int mult) @@ -106,17
> > > +144,31 @@ static int clk_pllv4_set_rate(struct clk_hw *hw, unsigned
> > > +long
> > rate, {
> > > struct clk_pllv4 *pll = to_clk_pllv4(hw);
> > > u32 val, mult;
> > > + u32 mfn, mfd = 1000000;
> > > + u32 max_mfd = 0x3FFFFFFF;
> >
> > Ditto
> >
> > Otherwise:
> > Reviewed-by: Dong Aisheng <aisheng.dong@....com>
> >
> > Regards
> > Dong Aisheng
> >
> > > + u64 temp64;
> > >
> > > mult = rate / parent_rate;
> > >
> > > if (!clk_pllv4_is_valid_mult(mult))
> > > return -EINVAL;
> > >
> > > + if (parent_rate <= max_mfd)
> > > + mfd = parent_rate;
> > > +
> > > + temp64 = (u64)(rate - mult * parent_rate);
> > > + temp64 *= mfd;
> > > + do_div(temp64, parent_rate);
> > > + mfn = temp64;
> > > +
> > > 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);
> > >
> > > + writel_relaxed(mfn, pll->base + PLL_NUM_OFFSET);
> > > + writel_relaxed(mfd, pll->base + PLL_DENOM_OFFSET);
> > > +
> > > return 0;
> > > }
> > >
> > > --
> > > 2.7.4
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