linux-kernel - Re: [PATCH 1/6] clk: stm32f4: Add PLL_I2S & PLL

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Date:   Tue, 8 Nov 2016 09:35:58 +0100
From:   Gabriel Fernandez <gabriel.fernandez@...com>
To:     Radosław Pietrzyk <radoslaw.pietrzyk@...il.com>
CC:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Nicolas Pitre <nico@...aro.org>, Arnd Bergmann <arnd@...db.de>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Andrea Merello <andrea.merello@...il.com>,
        <devicetree@...r.kernel.org>, <amelie.delaunay@...com>,
        <kernel@...inux.com>, <olivier.bideau@...com>,
        <linux-kernel@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <ludovic.barre@...com>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/6] clk: stm32f4: Add PLL_I2S & PLL_SAI for STM32F429/469
 boards

Hi Radosław

Many thanks for reviewing.

On 11/07/2016 03:57 PM, Radosław Pietrzyk wrote:
>> +static struct clk_hw *clk_register_pll_div(const char *name,
>> +               const char *parent_name, unsigned long flags,
>> +               void __iomem *reg, u8 shift, u8 width,
>> +               u8 clk_divider_flags, const struct clk_div_table *table,
>> +               struct clk_hw *pll_hw, spinlock_t *lock)
>> +{
>> +       struct stm32f4_pll_div *pll_div;
>> +       struct clk_hw *hw;
>> +       struct clk_init_data init;
>> +       int ret;
>> +
>> +       /* allocate the divider */
>> +       pll_div = kzalloc(sizeof(*pll_div), GFP_KERNEL);
>> +       if (!pll_div)
>> +               return ERR_PTR(-ENOMEM);
>> +
>> +       init.name = name;
>> +       init.ops = &stm32f4_pll_div_ops;
>> +       init.flags = flags;
> Maybe it's worth to have CLK_SET_RATE_PARENT here and the VCO clock
> should have CLK_SET_RATE_GATE flag and we can get rid of custom
> divider ops.
I don't want to offer the possibility to change the vco clock through 
the divisor of the pll (only by a boot-loader or by DT).

e.g. if i make a set rate on lcd-tft clock, i don't want to change the 
SAI frequencies.

I used same structure for internal divisors of the pll (p, q, r) and for 
post divisors (plli2s-q-div, pllsai-q-div & pllsai-r-div).
That why the CLK_SET_RATE_PARENT flag is transmit by parameter.

These divisors are similar because we have to switch off the pll before 
changing the rate.

>
>
>> -static void stm32f4_rcc_register_pll(const char *hse_clk, const char *hsi_clk)
>> +
>> +static struct clk_hw *stm32f4_rcc_register_pll(const char *pllsrc,
>> +               const struct stm32f4_pll_data *data,  spinlock_t *lock)
>>   {
>> -       unsigned long pllcfgr = readl(base + STM32F4_RCC_PLLCFGR);
>> +       struct stm32f4_pll *pll;
>> +       struct clk_init_data init = { NULL };
>> +       void __iomem *reg;
>> +       struct clk_hw *pll_hw;
>> +       int ret;
>> +
>> +       pll = kzalloc(sizeof(*pll), GFP_KERNEL);
>> +       if (!pll)
>> +               return ERR_PTR(-ENOMEM);
>> +
>> +       init.name = data->vco_name;
>> +       init.ops = &stm32f4_pll_gate_ops;
>> +       init.flags = CLK_IGNORE_UNUSED;
> CLK_SET_RATE_GATE here
>
> Moreover why not having VCO as a composite clock from gate and mult ?
Yes, that sounds a good idea.

> According to docs SAI VCO (don't know about I2S ) must be within
> certain range so clk_set_rate_range should be somewhere.