[PATCH V1 7/9] clk: sprd: add adjustable pll support

[zhang.lyra@gmail.com (Chunyan Zhang)]

Hi Stephen,

On 30 June 2017 at 09:44, Stephen Boyd <sboyd@codeaurora.org> wrote:
> On 06/22, Chunyan Zhang wrote:
>> On 20 June 2017 at 09:37, Stephen Boyd <sboyd@codeaurora.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

>
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