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Message-ID: <CAAfSe-smKqgd42jDAGDA=NtYvRZExNanU7fHrRkT4W-WH-2=ug@mail.gmail.com>
Date: Fri, 30 Jun 2017 15:55:42 +0800
From: Chunyan Zhang <zhang.lyra@...il.com>
To: Stephen Boyd <sboyd@...eaurora.org>
Cc: Chunyan Zhang <chunyan.zhang@...eadtrum.com>,
Michael Turquette <mturquette@...libre.com>,
Rob Herring <robh+dt@...nel.org>,
Mark Rutland <mark.rutland@....com>,
linux-clk <linux-clk@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
Arnd Bergmann <arnd@...db.de>, Mark Brown <broonie@...nel.org>,
Xiaolong Zhang <xiaolong.zhang@...eadtrum.com>,
Orson Zhai <orson.zhai@...eadtrum.com>,
Geng Ren <geng.ren@...eadtrum.com>,
Ben Li <ben.li@...eadtrum.com>
Subject: Re: [PATCH V1 7/9] clk: sprd: add adjustable pll support
Hi Stephen,
On 30 June 2017 at 09:44, Stephen Boyd <sboyd@...eaurora.org> wrote:
> On 06/22, Chunyan Zhang wrote:
>> On 20 June 2017 at 09:37, Stephen Boyd <sboyd@...eaurora.org> wrote:
>> > On 06/18, Chunyan Zhang wrote:
>> >> diff --git a/drivers/clk/sprd/Makefile b/drivers/clk/sprd/Makefile
>> >> index 83232e5..c593a93 100644
>> >> --- a/drivers/clk/sprd/Makefile
>> >> +++ b/drivers/clk/sprd/Makefile
>> >> @@ -1,3 +1,3 @@
>> >> ifneq ($(CONFIG_OF),)
>> >> -obj-y += ccu_common.o ccu_gate.o ccu_mux.o ccu_div.o ccu_composite.o
>> >> +obj-y += ccu_common.o ccu_gate.o ccu_mux.o ccu_div.o ccu_composite.o ccu_pll.o
>> >> endif
>> >> diff --git a/drivers/clk/sprd/ccu_pll.c b/drivers/clk/sprd/ccu_pll.c
>> >> new file mode 100644
>> >> index 0000000..6c908e4
>> >> --- /dev/null
>> >> +++ b/drivers/clk/sprd/ccu_pll.c
>> >> @@ -0,0 +1,241 @@
>> >> +/*
>> >> + * Spreadtrum pll clock driver
>> >> + *
>> >> + * Copyright (C) 2015~2017 Spreadtrum, Inc.
>> >> + *
>> >> + * SPDX-License-Identifier: GPL-2.0
>> >> + */
>> >> +
>> >> +#include <linux/delay.h>
>> >> +#include <linux/clk.h>
>> >
>> > Is this include used? Should be clk-provider?
>>
>> Right, will remove it.
>>
>> >
>> >> +#include <linux/err.h>
>> >> +#include <linux/slab.h>
>> >> +
>> >> +#include "ccu_pll.h"
>> >> +
>> >> +#define CCU_PLL_1M 1000000
>> >> +#define CCU_PLL_10M (CCU_PLL_1M * 10)
>> >> +
>> >> +#define pindex(pll, member) \
>> >> + (pll->factors[member].shift / (8 * sizeof(pll->regs[0])))
>> >> +
>> >> +#define pshift(pll, member) \
>> >> + (pll->factors[member].shift % (8 * sizeof(pll->regs[0])))
>> >> +
>> >> +#define pwidth(pll, member) \
>> >> + pll->factors[member].width
>> >> +
>> >> +#define pmask(pll, member) \
>> >> + ((pwidth(pll, member)) ? \
>> >> + GENMASK(pwidth(pll, member) + pshift(pll, member) - 1, \
>> >> + pshift(pll, member)) : 0)
>> >> +
>> >> +#define pinternal(pll, cfg, member) \
>> >> + (cfg[pindex(pll, member)] & pmask(pll, member))
>> >> +
>> >> +#define pinternal_val(pll, cfg, member) \
>> >> + (pinternal(pll, cfg, member) >> pshift(pll, member))
>> >> +
>> >> +static unsigned long pll_get_refin_rate(struct ccu_pll *pll)
>> >
>> > pll could be const?
>>
>> What this function returns is a factor used to calculate the pll rate
>> later, I will rename this function in the next iterator.
>>
>
> Rename is fine, but pll can still be marked const?
Oh, sorry I misunderstood :)
You mean mark the input parameter "pll" const, right?
>>
>> >
>> >> + nint = pinternal_val(pll, cfg, PLL_NINT);
>> >> + if (pinternal(pll, cfg, PLL_SDM_EN))
>> >> + kint = pinternal_val(pll, cfg, PLL_KINT);
>> >> +
>> >> + mask = pmask(pll, PLL_KINT);
>> >> +#ifdef CONFIG_64BIT
>> >> + k1 = 1000;
>> >> + k2 = 1000;
>> >> + rate = DIV_ROUND_CLOSEST(refin * kint * k1,
>> >> + ((mask >> __ffs(mask)) + 1)) *
>> >> + k2 + refin * nint * CCU_PLL_1M;
>> >> +#else
>> >> + k1 = 100;
>> >> + k2 = 10000;
>> >> + i = pwidth(pll, PLL_KINT);
>> >> + i = i < 21 ? 0 : i - 21;
>> >> + rate = DIV_ROUND_CLOSEST(refin * (kint >> i) * k1,
>> >> + ((mask >> (__ffs(mask) + i)) + 1)) *
>> >> + k2 + refin * nint * CCU_PLL_1M;
>> >> +#endif
>> >> + }
>> >> +
>> >> + return rate;
>> >> +}
>> >> +
>> >> +static int ccu_pll_helper_set_rate(struct ccu_pll *pll,
>> >> + unsigned long rate,
>> >> + unsigned long parent_rate)
>> >> +{
>> >> + u32 mask, shift, width, ibias_val, index, kint, nint;
>> >> + u32 reg_num = pll->regs[0], i = 0;
>> >> + unsigned long refin, fvco = rate;
>> >> + struct reg_cfg *cfg;
>> >> +
>> >> + cfg = kcalloc(reg_num, sizeof(*cfg), GFP_KERNEL);
>> >> + if (!cfg)
>> >> + return -ENOMEM;
>> >> +
>> >> + refin = pll_get_refin_rate(pll);
>> >> +
>> >> + mask = pmask(pll, PLL_PREDIV);
>> >> + index = pindex(pll, PLL_PREDIV);
>> >> + width = pwidth(pll, PLL_PREDIV);
>> >> + if (width && (ccu_pll_readl(pll, index) & mask))
>> >> + refin = refin * 2;
>> >> +
>> >> + mask = pmask(pll, PLL_POSTDIV);
>> >> + index = pindex(pll, PLL_POSTDIV);
>> >> + width = pwidth(pll, PLL_POSTDIV);
>> >> + cfg[index].msk = mask;
>> >> + if (width && ((pll->fflag == 1 && fvco <= pll->fvco) ||
>> >> + (pll->fflag == 0 && fvco > pll->fvco)))
>> >> + cfg[index].val |= mask;
>> >> +
>> >> + if (width && fvco <= pll->fvco)
>> >> + fvco = fvco * 2;
>> >> +
>> >> + mask = pmask(pll, PLL_DIV_S);
>> >> + index = pindex(pll, PLL_DIV_S);
>> >> + cfg[index].val |= mask;
>> >> + cfg[index].msk |= mask;
>> >> +
>> >> + mask = pmask(pll, PLL_SDM_EN);
>> >> + index = pindex(pll, PLL_SDM_EN);
>> >> + cfg[index].val |= mask;
>> >> + cfg[index].msk |= mask;
>> >> +
>> >> + nint = fvco/(refin * CCU_PLL_1M);
>> >> +
>> >> + mask = pmask(pll, PLL_NINT);
>> >> + index = pindex(pll, PLL_NINT);
>> >> + shift = pshift(pll, PLL_NINT);
>> >> + cfg[index].val |= (nint << shift) & mask;
>> >> + cfg[index].msk |= mask;
>> >> +
>> >> + mask = pmask(pll, PLL_KINT);
>> >> + index = pindex(pll, PLL_KINT);
>> >> + width = pwidth(pll, PLL_KINT);
>> >> + shift = pshift(pll, PLL_KINT);
>> >> +#ifndef CONFIG_64BIT
>> >> + i = width < 21 ? 0 : i - 21;
>> >> +#endif
>> >
>> > What's this? Why do we depend on CONFIG_64BIT?
>>
>> On 32-bit SoCs, the largest width we can support is limited due to the
>> limitation of calculation precision.
>
> Does the hardware width change? Still not clear to me what's
> going on here.
I heard from my colleague, that because the calculation precision on
Spreadtrum's 32-bit SoCs is different from on 64-bit SoCs, when the
width of the value of PLL_KINT is larger than 21, the value is too
large to be multiplied on 32-bit Spreadtrum's SoCs.
i = width < 21 ? 0 : i - 21;
Here ' i ' is used to adjust 'shift' rather than 'width' like below (
wrote the code back for convenience of understanding)
+ kint = DIV_ROUND_CLOSEST(((fvco - refin * nint * CCU_PLL_1M)/10000) *
+ ((mask >> (shift + i)) + 1), refin * 100) << i;
Thanks for your review,
Chunyan
>
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> a Linux Foundation Collaborative Project
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