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Date: Fri, 20 Jan 2023 11:33:52 +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 <neil.armstrong@...aro.org>,
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>
CC: "kelvin . zhang" <Kelvin.Zhang@...ogic.com>,
"qi . duan" <qi.duan@...ogic.com>
Subject: Re: [PATCH V6 3/3] clk: meson: s4: add support for Amlogic S4 SoC
peripheral clock controller
Hi
On 2023/1/19 19:37, Jerome Brunet wrote:
> [ EXTERNAL EMAIL ]
>
>
> On Mon 16 Jan 2023 at 15:42, Yu Tu <yu.tu@...ogic.com> wrote:
>
>> Add the peripherals clock controller driver in the s4 SoC family.
>>
>> Signed-off-by: Yu Tu <yu.tu@...ogic.com>
>
> [...]
>
>> +
>> +/* 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",
>> + /*
>> + * The frequency division from the hdmi_pll clock to the vid_pll_div
>> + * clock is the default value of this register. When designing the
>> + * video module of the chip, a default value that can meet the
>> + * requirements of the video module will be solidified according
>> + * to the usage requirements of the chip, so as to facilitate chip
>> + * simulation. So this is ro_ops.
>> + * It is important to note that this clock is not used on this
>> + * chip and is described only for the integrity of the clock tree.
>> + */
>
> If it is reset value and will be applicable to all the design, regarless
> of the use-case, then yes RO ops is OK
>
>>>From what I understand here, the value will depend on the use-case requirements.
> This is a typical case where the DT prop "assigned-rate" should be used, not RO ops.
Check the previous chip history, the actual scene is not used at all,
basically is used in simulation. So the previous SOC was "ro_ops"
without any problems. This S4 SOC is not actually useful either.
So when you were upstream, you had no problem making "ro_ops". I wonder
if I could delete this useless clock, so you don't have to worry about it.
>
>> + .ops = &meson_vid_pll_div_ro_ops,
>> + .parent_data = (const struct clk_parent_data []) {
>> + { .fw_name = "hdmi_pll", }
>> + },
>> + .num_parents = 1,
>> + .flags = CLK_SET_RATE_PARENT,
>> + },
>> +};
>> +
>
>> +
>> +/* VDEC clocks */
>> +static const struct clk_parent_data s4_dec_parent_data[] = {
>> + { .fw_name = "fclk_div2p5", },
>> + { .fw_name = "fclk_div3", },
>> + { .fw_name = "fclk_div4", },
>> + { .fw_name = "fclk_div5", },
>> + { .fw_name = "fclk_div7", },
>> + { .fw_name = "hifi_pll", },
>> + { .fw_name = "gp0_pll", },
>> + { .fw_name = "xtal", }
>> +};
>> +
>> +static struct clk_regmap s4_vdec_p0_mux = {
>> + .data = &(struct clk_regmap_mux_data){
>> + .offset = CLKCTRL_VDEC_CLK_CTRL,
>> + .mask = 0x7,
>> + .shift = 9,
>> + .flags = CLK_MUX_ROUND_CLOSEST,
>> + },
>> + .hw.init = &(struct clk_init_data) {
>> + .name = "vdec_p0_mux",
>> + .ops = &clk_regmap_mux_ops,
>> + .parent_data = s4_dec_parent_data,
>> + .num_parents = ARRAY_SIZE(s4_dec_parent_data),
>> + /*
>> + * When the driver uses this clock, needs to specify the patent clock
>> + * he wants in the dts.
>
> s/patent/parent ?
> s/he wants/it requires ?
Okay.
>
>> + */
>> + .flags = CLK_SET_RATE_NO_REPARENT | CLK_SET_RATE_PARENT,
>> + },
>> +};
>> +
>
> [...]
>
>> +static const struct clk_parent_data s4_vpu_clkc_parent_data[] = {
>> + { .fw_name = "fclk_div4", },
>> + { .fw_name = "fclk_div3", },
>> + { .fw_name = "fclk_div5", },
>> + { .fw_name = "fclk_div7", },
>> + { .fw_name = "mpll1", },
>> + { .hw = &s4_vid_pll.hw },
>> + { .fw_name = "mpll2", },
>> + { .fw_name = "gp0_pll", },
>> +};
>> +
>> +static struct clk_regmap s4_vpu_clkc_p0_mux = {
>> + .data = &(struct clk_regmap_mux_data){
>> + .offset = CLKCTRL_VPU_CLKC_CTRL,
>> + .mask = 0x7,
>> + .shift = 9,
>> + },
>> + .hw.init = &(struct clk_init_data) {
>> + .name = "vpu_clkc_p0_mux",
>> + .ops = &clk_regmap_mux_ops,
>> + .parent_data = s4_vpu_clkc_parent_data,
>> + .num_parents = ARRAY_SIZE(s4_vpu_clkc_parent_data),
>> + /*
>> + * When the driver uses this clock, needs to specify the patent clock
>> + * he wants in the dts.
>> + */
>
> That's quite a lot of occurences of the same comment.
> At the same time, other clocks with the same flag have no comment.
>
> Please make general comment, before the Video/VPU section, explaining
> which clocks needs on a use-case basis (through DT) and possibly how it
> should be set, what should drive the choices.
>
The owner of the corresponding driver module wants to have a fixed
clock, but I can't explain every specific reason. So I'm going to change
it all to.flags = CLK_SET_RATE_PARENT in the next version. Let CCF
choose the appropriate clock as you suggested. If there is a
corresponding module you want to change, ask him to give you a specific
explanation. Do you think that's all right?
I will not reply to you below.
>> + .flags = CLK_SET_RATE_NO_REPARENT | 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", },
>> + { .fw_name = "mpll2", },
>> + { .fw_name = "mpll3", },
>> + { .fw_name = "gp0_pll", },
>> +};
>> +
>> +static struct clk_regmap s4_sd_emmc_c_clk0_sel = {
>> + .data = &(struct clk_regmap_mux_data){
>> + .offset = CLKCTRL_NAND_CLK_CTRL,
>> + .mask = 0x7,
>> + .shift = 9,
>> + },
>> + .hw.init = &(struct clk_init_data) {
>> + .name = "sd_emmc_c_clk0_sel",
>> + .ops = &clk_regmap_mux_ops,
>> + .parent_data = s4_sd_emmc_clk0_parent_data,
>> + .num_parents = ARRAY_SIZE(s4_sd_emmc_clk0_parent_data),
>> + /*
>> + * When the driver uses this clock, needs to specify the patent clock
>> + * he wants in the dts.
>> + */
>
> I'm getting a bit suspicious about the use (and abuse ...) of this flag.
> I don't quite get how selecting the base PLL for MMC should be done on
> use-case basis and should be up the board DT ...
>
> Other SoC have all used fdiv2 so far. Do you expect this setting to be
> part of the dtsi SoC file ?
>
>> + .flags = CLK_SET_RATE_NO_REPARENT | CLK_SET_RATE_PARENT,
>> + },
>> +};
>> +
>
>> +
>> +/* SPICC Clock */
>> +static const struct clk_parent_data s4_spicc_parent_data[] = {
>> + { .fw_name = "xtal", },
>> + { .hw = &s4_sys_clk.hw },
>> + { .fw_name = "fclk_div4", },
>> + { .fw_name = "fclk_div3", },
>> + { .fw_name = "fclk_div2", },
>> + { .fw_name = "fclk_div5", },
>> + { .fw_name = "fclk_div7", },
>> +};
>> +
>> +static struct clk_regmap s4_spicc0_mux = {
>> + .data = &(struct clk_regmap_mux_data){
>> + .offset = CLKCTRL_SPICC_CLK_CTRL,
>> + .mask = 0x7,
>> + .shift = 7,
>> + },
>> + .hw.init = &(struct clk_init_data) {
>> + .name = "spicc0_mux",
>> + .ops = &clk_regmap_mux_ops,
>> + .parent_data = s4_spicc_parent_data,
>> + .num_parents = ARRAY_SIZE(s4_spicc_parent_data),
>> + /*
>> + * When the driver uses this clock, needs to specify the patent clock
>> + * he wants in the dts.
>> + */
>
> This is getting too far. All the parent clocks are fixed.
> Let CCF do the job of picking the most adequate clock for the job
> instead of manually settings things
>
>> + .flags = CLK_SET_RATE_NO_REPARENT | CLK_SET_RATE_PARENT,
>> + },
>> +};
>> +
>
>
>> +
>> +/* PWM Clock */
>> +static const struct clk_parent_data s4_pwm_parent_data[] = {
>> + { .fw_name = "xtal", },
>> + { .hw = &s4_vid_pll.hw },
>> + { .fw_name = "fclk_div4", },
>> + { .fw_name = "fclk_div3", },
>> +};
>> +
>> +static struct clk_regmap s4_pwm_a_mux = {
>> + .data = &(struct clk_regmap_mux_data) {
>> + .offset = CLKCTRL_PWM_CLK_AB_CTRL,
>> + .mask = 0x3,
>> + .shift = 9,
>> + },
>> + .hw.init = &(struct clk_init_data){
>> + .name = "pwm_a_mux",
>> + .ops = &clk_regmap_mux_ops,
>> + .parent_data = s4_pwm_parent_data,
>> + .num_parents = ARRAY_SIZE(s4_pwm_parent_data),
>> + /*
>> + * When the driver uses this clock, needs to specify the patent clock
>> + * he wants in the dts.
>> + */
>
> Same here ... this is really going to far.
>
>> + .flags = CLK_SET_RATE_NO_REPARENT | CLK_SET_RATE_PARENT,
>> + },
>> +};
>> +
>
>> +
>> +static struct clk_regmap s4_saradc_mux = {
>> + .data = &(struct clk_regmap_mux_data) {
>> + .offset = CLKCTRL_SAR_CLK_CTRL,
>> + .mask = 0x3,
>> + .shift = 9,
>> + },
>> + .hw.init = &(struct clk_init_data){
>> + .name = "saradc_mux",
>> + .ops = &clk_regmap_mux_ops,
>> + .parent_data = (const struct clk_parent_data []) {
>> + { .fw_name = "xtal", },
>> + { .hw = &s4_sys_clk.hw },
>> + },
>> + .num_parents = 2,
>> + /*
>> + * When the driver uses this clock, needs to specify the patent clock
>> + * he wants in the dts.
>> + */
>
> For each clock type, if this flag is going to be used, I'd like a clear
> explanation about why it is use-case dependent and why you need manual
> control over this. Same applies to all the occurence.
>
>> + .flags = CLK_SET_RATE_NO_REPARENT | CLK_SET_RATE_PARENT,
>> + },
>> +};
>
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