Message-ID: <2b6035f3-8cbe-ab75-bed9-5751b141d3d6@amlogic.com>
Date:   Tue, 30 Aug 2022 16:20:05 +0800
From:   Yu Tu <yu.tu@...ogic.com>
To:     Jerome Brunet <jbrunet@...libre.com>, <linux-clk@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH V3 6/6] clk: meson: s4: add s4 SoC peripheral clock
 controller driver



On 2022/8/29 20:19, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
> 
> 
> On Tue 16 Aug 2022 at 20:00, Yu Tu <yu.tu@...ogic.com> wrote:
> 
> Please trim your replies
> 
>>>> diff --git a/drivers/clk/meson/Kconfig b/drivers/clk/meson/Kconfig
>>>> index f4244edc7b28..ec6beb9284d3 100644
>>>> --- a/drivers/clk/meson/Kconfig
>>>> +++ b/drivers/clk/meson/Kconfig
>>>> @@ -127,4 +127,17 @@ config COMMON_CLK_S4_PLL
>>>>    	  Support for the pll clock controller on Amlogic S805X2 and S905Y4 devices,
>>>>    	  aka s4. Amlogic S805X2 and S905Y4 devices include AQ222 and AQ229.
>>>>    	  Say Y if you want peripherals and CPU frequency scaling to work.
>>>> +
>>>> +config COMMON_CLK_S4
>>>> +	tristate "S4 SoC Peripherals clock controllers support"
>>>> +	depends on ARM64
>>>> +	default y
>>>> +	select COMMON_CLK_MESON_REGMAP
>>>> +	select COMMON_CLK_MESON_DUALDIV
>>>> +	select COMMON_CLK_MESON_VID_PLL_DIV
>>>> +	select COMMON_CLK_S4_PLL
>>> Do you really this ? your driver does not even include the related
>>> header.
>> If the PLL driver is not turned on in DTS, will it not cause an error?
>>>
> 
> I don't get the question.
> Kconfig list compile deps. S4 PLL is not a compile dep of the peripheral
> controller.
> 
> If you really want to, you may use 'imply'.

V4 has been changed as you suggested.

>>>
>>>> +static const struct clk_parent_data sys_ab_clk_parent_data[] = {
>>>> +	{ .fw_name = "xtal" },
>>>> +	{ .fw_name = "fclk_div2" },
>>>> +	{ .fw_name = "fclk_div3" },
>>>> +	{ .fw_name = "fclk_div4" },
>>>> +	{ .fw_name = "fclk_div5" },
>>>> +	{ .fw_name = "fclk_div7" },
>>>> +	{ .hw = &s4_rtc_clk.hw }
>>>> +};
>>>> +
>>>> +static struct clk_regmap s4_sysclk_b_sel = {
>>>> +	.data = &(struct clk_regmap_mux_data){
>>>> +		.offset = CLKCTRL_SYS_CLK_CTRL0,
>>>> +		.mask = 0x7,
>>>> +		.shift = 26,
>>>> +		.table = mux_table_sys_ab_clk_sel,
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data){
>>>> +		.name = "sysclk_b_sel",
>>>> +		.ops = &clk_regmap_mux_ro_ops,
>>> Why is this using the RO ops ?
>> Sys_clk is initialized during the Uboot phase and is fixed at
>> 166.666MHz. So I'm going to change it to ro.
> 
> That really much depends on the bootloader and is a pretty weak design.
> The bootloader deps should be kept as minimal as possible.
> 
> I see no reason for RO.
> 
> You may cut rate propagation on the user if you need to and continue to
> whatever you want in your u-boot

I think I know what you mean. But we let the user be in control and not 
set the frequency, which can be risky. If you insist, I will change it 
as you suggest.

> 
>>>
>>>> +		.parent_data = sys_ab_clk_parent_data,
>>>> +		.num_parents = ARRAY_SIZE(sys_ab_clk_parent_data),
>>>> +	},
>>>> +};
>>>> +
>>>> +static struct clk_regmap s4_sysclk_b_div = {
>>>> +	.data = &(struct clk_regmap_div_data){
>>>> +		.offset = CLKCTRL_SYS_CLK_CTRL0,
>>>> +		.shift = 16,
>>>> +		.width = 10,
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data){
>>>> +		.name = "sysclk_b_div",
>>>> +		.ops = &clk_regmap_divider_ro_ops,
>>> Same here and for the rest of the sys part
>> Same above.
> 
> We can play that game for a while

Ah, you're so funny.

> 
>>>> +
>>>> +/* Video Clocks */
>>>> +static struct clk_regmap s4_vid_pll_div = {
>>>> +	.data = &(struct meson_vid_pll_div_data){
>>>> +		.val = {
>>>> +			.reg_off = CLKCTRL_VID_PLL_CLK_DIV,
>>>> +			.shift   = 0,
>>>> +			.width   = 15,
>>>> +		},
>>>> +		.sel = {
>>>> +			.reg_off = CLKCTRL_VID_PLL_CLK_DIV,
>>>> +			.shift   = 16,
>>>> +			.width   = 2,
>>>> +		},
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data) {
>>>> +		.name = "vid_pll_div",
>>>> +		.ops = &meson_vid_pll_div_ro_ops,
>>> Why RO ? applies to the rest of the video part.
>> Because vid_pll_div parent is HDMI_PLL, and HDMI_PLL is a fixed
>> frequency. Flags is CLK_SET_RATE_PARENT. So we use RO.
> 
> If the HDMI_PLL is fixed somehow, that is not reason for this clock to
> be RO
> 
>> Can I remove RO and use CLK_SET_RATE_NO_REPARENT instead, which one do you
>> think is more reasonable?
> 
> Neither. CLK_SET_RATE_NO_REPARENT makes no sense, it is not mux
> 

"drivers/clk/meson/vid-pll-div.c"
This file only provides ro_ops. Maybe the submission records will give 
us the answer.

In fact, our hardware design is the same as the G12 series.

>>
>>>
>>>> +		.parent_data = (const struct clk_parent_data []) {
>>>> +			{ .fw_name = "hdmi_pll", }
>>>> +		},
>>>> +		.num_parents = 1,
>>>> +		.flags = CLK_SET_RATE_PARENT,
>>>> +	},
>>>> +};
>>>> +
>>>> +static struct clk_regmap s4_vid_pll_sel = {
>>>> +	.data = &(struct clk_regmap_mux_data){
>>>> +		.offset = CLKCTRL_VID_PLL_CLK_DIV,
>>>> +		.mask = 0x1,
>>>> +		.shift = 18,
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data){
>>>> +		.name = "vid_pll_sel",
>>>> +		.ops = &clk_regmap_mux_ops,
>>>> +		/*
>>>> +		 * bit 18 selects from 2 possible parents:
>>>> +		 * vid_pll_div or hdmi_pll
>>>> +		 */
>>>> +		.parent_data = (const struct clk_parent_data []) {
>>>> +			{ .hw = &s4_vid_pll_div.hw },
>>>> +			{ .fw_name = "hdmi_pll", }
>>>> +		},
>>>> +		.num_parents = 2,
>>>> +		.flags = CLK_SET_RATE_NO_REPARENT,
>>> Why ? are you planning to DT assigned clocks to statically set this ?
>> Because vid_pll_sel one parent is HDMI_PLL, and HDMI_PLL is a fixed
>> frequency. To prevent modification, use CLK_SET_RATE_NO_REPARENT.
> 
> Again, this makes no sense.

Unfortunately you don't read V4, in fact I have corrected in V4.

".flags = CLK_SET_RATE_PARENT," in V4. Is that okay with you?

> 
>>>
>>>> +	},
>>>> +};
>>>> +
>>>> +static struct clk_regmap s4_vid_pll = {
>>>> +	.data = &(struct clk_regmap_gate_data){
>>>> +		.offset = CLKCTRL_VID_PLL_CLK_DIV,
>>>> +		.bit_idx = 19,
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data) {
>>>> +		.name = "vid_pll",
>>>> +		.ops = &clk_regmap_gate_ops,
>>>> +		.parent_hws = (const struct clk_hw *[]) {
>>>> +			&s4_vid_pll_sel.hw
>>>> +		},
>>>> +		.num_parents = 1,
>>>> +		.flags = CLK_SET_RATE_PARENT,
>>>> +	},
>>>> +};
>>>> +
>>>> +static const struct clk_parent_data s4_vclk_parent_data[] = {
>>>> +	{ .hw = &s4_vid_pll.hw },
>>>> +	{ .fw_name = "gp0_pll", },
>>>> +	{ .fw_name = "hifi_pll", },
>>>> +	{ .fw_name = "mpll1", },
>>>> +	{ .fw_name = "fclk_div3", },
>>>> +	{ .fw_name = "fclk_div4", },
>>>> +	{ .fw_name = "fclk_div5", },
>>>> +	{ .fw_name = "fclk_div7", },
>>>> +};
>>>> +
>>>> +static struct clk_regmap s4_vclk_sel = {
>>>> +	.data = &(struct clk_regmap_mux_data){
>>>> +		.offset = CLKCTRL_VID_CLK_CTRL,
>>>> +		.mask = 0x7,
>>>> +		.shift = 16,
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data){
>>>> +		.name = "vclk_sel",
>>>> +		.ops = &clk_regmap_mux_ops,
>>>> +		.parent_data = s4_vclk_parent_data,
>>>> +		.num_parents = ARRAY_SIZE(s4_vclk_parent_data),
>>>> +		.flags = CLK_SET_RATE_NO_REPARENT,
>>> Same
>> Since fclk_div* is a fixed frequency value, mplL1 and hifi_pll and gp0_pll
>> are used by other specialized modules, vid_pll has CLK_SET_RATE_PARENT. The
>> parent of vid_pll is that vid_pll_sel uses CLK_SET_RATE_NO_REPARENT.
> 
> Still not good.
> 
> You don't have CLK_SET_RATE, propagation is stopped and parent clock
> will not changed. The best parent will be picked but not changed.
> 
> If one parent MUST NOT be picked, just remove it from the list and add a
> explaining why
> 
> [...]

Okay.

> 
>>>> +
>>>> +static struct clk_regmap s4_ts_clk_div = {
>>>> +	.data = &(struct clk_regmap_div_data){
>>>> +		.offset = CLKCTRL_TS_CLK_CTRL,
>>>> +		.shift = 0,
>>>> +		.width = 8,
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data){
>>>> +		.name = "ts_clk_div",
>>>> +		.ops = &clk_regmap_divider_ops,
>>>> +		.parent_data = &(const struct clk_parent_data) {
>>>> +			.fw_name = "xtal",
>>>> +		},
>>>> +		.num_parents = 1,
>>> propagation stopped ?
>> Its parent is xtal, so I should use CLK_SET_RATE_NO_REPARENT.
> 
> Still no. You seem to have problem with the meaning of
> CLK_SET_RATE_NO_REPARENT.
> 
> * CLK_SET_RATE_NO_REPARENT: means the parent will no be changed, even if
>    selecting another parent would result in a closer rate to the
>    request. It makes sense only if the clock has several parents
> 
> * CLK_SET_RATE_PARENT: means rate change may propagate the parent,
>    meaning the rate of the parent may change if it help the child achieve
>    a closer rate to the request

Thank you for explaining.I got it.

> 
>>>
>>>> +	},
>>>> +};
>>>> +
>>>> +static struct clk_regmap s4_ts_clk_gate = {
>>>> +	.data = &(struct clk_regmap_gate_data){
>>>> +		.offset = CLKCTRL_TS_CLK_CTRL,
>>>> +		.bit_idx = 8,
>>>> +	},
>>>> +	.hw.init = &(struct clk_init_data){
>>>> +		.name = "ts_clk",
>>>> +		.ops = &clk_regmap_gate_ops,
>>>> +		.parent_hws = (const struct clk_hw *[]) {
>>>> +			&s4_ts_clk_div.hw
>>>> +		},
>>>> +		.num_parents = 1,
>>>> +	},
>>> propagation stopped ?
>> I will add CLK_SET_RATE_PARENT.
> 
> [...]
> 
>>>> +/* EMMC/NAND clock */
>>>> +
>>>> +static const struct clk_parent_data s4_sd_emmc_clk0_parent_data[] = {
>>>> +	{ .fw_name = "xtal", },
>>>> +	{ .fw_name = "fclk_div2", },
>>>> +	{ .fw_name = "fclk_div3", },
>>>> +	{ .fw_name = "hifi_pll", },
>>>> +	{ .fw_name = "fclk_div2p5", },
>>>> +	/*
>>>> +	 * Following these parent clocks, we should also have had mpll2, mpll3
>>>> +	 * and gp0_pll but these clocks are too precious to be used here. All
>>>> +	 * the necessary rates for MMC and NAND operation can be acheived using
>>>> +	 * hifi_pll or fclk_div clocks
>>>> +	 */
>>> You don't want to list mplls but hifi_pll is fine ? seems dangerous.
>> hifi pll is for EMMC and NAND on this SoC.
> 
> That deserve a better explanation.
> Why can't it use fdiv2 and xtal like the previous SoCs ?
> 
> Which PLLs are you using for Audio then ?
> Typical operation on these SoCs usually require 3 PLLs to acheive all rates
> 

I'll list all the clocks and let the driver itself select Parent as needed.

>>>
> 
> 
>>>> +/*
>>>> + * gen clk is designed for debug/monitor some internal clock quality. Some of the
>>>> + * corresponding clock sources are not described in the clock tree, so they are skipped.
>>>> + */
>>> Still feels a bit light, don't you think ? Among all the clocks, can't
>>> you add a bit more parents here ? It would certainly help debug down the road
>> [16:12]	is gen_clk source select.All is:
>> 0: cts_oscin_clk
>> 1:cts_rtc_clk
>> 2:sys_pll_div16 (internal clock)
>> 3:ddr_pll_div32  (internal clock)
>> 4: vid_pll
>> 5: gp0_pll
>> 7: hifi_pll
>> 10:adc_dpll_clk_b3 (internal clock for debug)
>> 11:adc_dpll_intclk (internal clock for debug)
>> 12:clk_msr_src(select from all internal clock except PLLs);
>> 16: no used
>> 17: sys_cpu_clk_div16 (internal clock)
>> 19: fclk_div2
>> 20: fclk_div2p5
>> 21: fclk_div3
>> 22: fclk_div4
>> 23: fclk_div5
>> 24: fclk_div7
>> 25: mpll0
>> 26: mpll1
>> 27: mpll2
>> 28: mpll3
>> So i only added the clocks that will actually be used, and some debugging
>> clock peripherals will not be used.
> 
> you may at least add vid_pll

Okay.

> 
>>>
>>>> +static u32 s4_gen_clk_mux_table[] = { 0, 5, 7, 19, 21, 22,
>>>> +				      23, 24, 25, 26, 27, 28 };
>>>> +static const struct clk_parent_data s4_gen_clk_parent_data[] = {
>>>> +	{ .fw_name = "xtal", },
>>>> +	{ .fw_name = "gp0_pll", },
>>>> +	{ .fw_name = "hifi_pll", },
>>>> +	{ .fw_name = "fclk_div2", },
>>>> +	{ .fw_name = "fclk_div3", },
>>>> +	{ .fw_name = "fclk_div4", },
>>>> +	{ .fw_name = "fclk_div5", },
>>>> +	{ .fw_name = "fclk_div7", },
>>>> +	{ .fw_name = "mpll0", },
>>>> +	{ .fw_name = "mpll1", },
>>>> +	{ .fw_name = "mpll2", },
>>>> +	{ .fw_name = "mpll3", },
>>>> +};
> 
> .

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