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Date:   Mon, 14 Nov 2022 19:22:02 +0100
From:   Marco Felsch <m.felsch@pengutronix.de>
To:     Dario Binacchi <dario.binacchi@amarulasolutions.com>
Cc:     linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Stephen Boyd <sboyd@kernel.org>,
        linux-amarula@amarulasolutions.com,
        Michael Turquette <mturquette@baylibre.com>,
        linux-clk@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
        NXP Linux Team <linux-imx@nxp.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Shawn Guo <shawnguo@kernel.org>, michael@amarulasolutions.com,
        Fabio Estevam <festevam@gmail.com>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        linux-arm-kernel@lists.infradead.org,
        Abel Vesa <abelvesa@kernel.org>
Subject: Re: [PATCH 1/5] clk: imx8mn: rename vpu_pll to m7_alt_pll
Message-ID: <20221114182202.ejt3ug7vgjuvvkz5@pengutronix.de>
References: <20221113180710.1625410-1-dario.binacchi@amarulasolutions.com>
 <20221113180710.1625410-2-dario.binacchi@amarulasolutions.com>
 <20221114083405.lpy2fjslfg644wex@pengutronix.de>
 <CABGWkvoBnq7PCzbAcF1oFVr0ydnpWPs5z7vLWBAnuectetMoDw@mail.gmail.com>
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Hi Dario,

On 22-11-14, Dario Binacchi wrote:
> Hi Marco,
> 
> On Mon, Nov 14, 2022 at 9:34 AM Marco Felsch <m.felsch@pengutronix.de> wrote:
> >
> > Hi Dario,
> >
> > On 22-11-13, Dario Binacchi wrote:
> > > There is no occurrence of vpu pll in the reference manual (document
> > > IMX8MNRM Rev 2, 07/2022). From an analysis of the code and the RM
> > > itself, I think vpu pll is used instead of m7 alternate pll, probably
> > > for copy and paste of code taken from modules of similar architectures.
> > >
> > > As an example for all, if we consider the second row of the "Clock Root"
> > > table of chapter 5 (Clocks and Power Management) of the RM:
> > >
> > >      Clock Root     offset     Source Select (CCM_TARGET_ROOTn[MUX])
> > >         ...          ...                    ...
> > >   ARM_M7_CLK_ROOT   0x8080            000 - 24M_REF_CLK
> > >                                       001 - SYSTEM_PLL2_DIV5
> > >                                     010 - SYSTEM_PLL2_DIV4
> > >                                     011 - M7_ALT_PLL_CLK
> > >                                     100 - SYSTEM_PLL1_CLK
> > >                                     101 - AUDIO_PLL1_CLK
> > >                                     110 - VIDEO_PLL_CLK
> > >                                     111 - SYSTEM_PLL3_CLK
> > >         ...          ...                    ...
> > >
> > > but in the source code, the imx8mn_m7_sels clocks list contains vpu_pll
> > > for the source select bits 011b.
> >
> > Thanks for the real detailed description. Maybe we should mention, that
> > the 8MN has no VPU complex at all.
> >
> > > So, let's rename "vpu_pll" to "m7_alt_pll" to be consistent with the RM.
> > >
> > > No functional changes intended.
> > >
> > > Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
> > > ---
> > >
> > >  drivers/clk/imx/clk-imx8mn.c             | 16 ++++++++--------
> > >  include/dt-bindings/clock/imx8mn-clock.h |  8 ++++----
> > >  2 files changed, 12 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/drivers/clk/imx/clk-imx8mn.c b/drivers/clk/imx/clk-imx8mn.c
> > > index d37c45b676ab..72f9563a0ff6 100644
> > > --- a/drivers/clk/imx/clk-imx8mn.c
> > > +++ b/drivers/clk/imx/clk-imx8mn.c
> > > @@ -30,7 +30,7 @@ static const char * const audio_pll2_bypass_sels[] = {"audio_pll2", "audio_pll2_
> > >  static const char * const video_pll1_bypass_sels[] = {"video_pll1", "video_pll1_ref_sel", };
> > >  static const char * const dram_pll_bypass_sels[] = {"dram_pll", "dram_pll_ref_sel", };
> > >  static const char * const gpu_pll_bypass_sels[] = {"gpu_pll", "gpu_pll_ref_sel", };
> > > -static const char * const vpu_pll_bypass_sels[] = {"vpu_pll", "vpu_pll_ref_sel", };
> > > +static const char * const m7_alt_pll_bypass_sels[] = {"m7_alt_pll", "m7_alt_pll_ref_sel", };
> > >  static const char * const arm_pll_bypass_sels[] = {"arm_pll", "arm_pll_ref_sel", };
> > >  static const char * const sys_pll3_bypass_sels[] = {"sys_pll3", "sys_pll3_ref_sel", };
> > >
> > > @@ -40,7 +40,7 @@ static const char * const imx8mn_a53_sels[] = {"osc_24m", "arm_pll_out", "sys_pl
> > >
> > >  static const char * const imx8mn_a53_core_sels[] = {"arm_a53_div", "arm_pll_out", };
> > >
> > > -static const char * const imx8mn_m7_sels[] = {"osc_24m", "sys_pll2_200m", "sys_pll2_250m", "vpu_pll_out",
> > > +static const char * const imx8mn_m7_sels[] = {"osc_24m", "sys_pll2_200m", "sys_pll2_250m", "m7_alt_pll_out",
> > >                                      "sys_pll1_800m", "audio_pll1_out", "video_pll1_out", "sys_pll3_out", };
> > >
> > >  static const char * const imx8mn_gpu_core_sels[] = {"osc_24m", "gpu_pll_out", "sys_pll1_800m",
> > > @@ -252,10 +252,10 @@ static const char * const imx8mn_gpt6_sels[] = {"osc_24m", "sys_pll2_100m", "sys
> > >                                               "audio_pll1_out", "clk_ext1", };
> > >
> > >  static const char * const imx8mn_wdog_sels[] = {"osc_24m", "sys_pll1_133m", "sys_pll1_160m",
> > > -                                             "vpu_pll_out", "sys_pll2_125m", "sys_pll3_out",
> > > +                                             "m7_alt_pll_out", "sys_pll2_125m", "sys_pll3_out",
> > >                                               "sys_pll1_80m", "sys_pll2_166m", };
> > >
> > > -static const char * const imx8mn_wrclk_sels[] = {"osc_24m", "sys_pll1_40m", "vpu_pll_out",
> > > +static const char * const imx8mn_wrclk_sels[] = {"osc_24m", "sys_pll1_40m", "m7_alt_pll_out",
> > >                                                "sys_pll3_out", "sys_pll2_200m", "sys_pll1_266m",
> > >                                                "sys_pll2_500m", "sys_pll1_100m", };
> > >
> > > @@ -352,7 +352,7 @@ static int imx8mn_clocks_probe(struct platform_device *pdev)
> > >       hws[IMX8MN_VIDEO_PLL1_REF_SEL] = imx_clk_hw_mux("video_pll1_ref_sel", base + 0x28, 0, 2, pll_ref_sels, ARRAY_SIZE(pll_ref_sels));
> > >       hws[IMX8MN_DRAM_PLL_REF_SEL] = imx_clk_hw_mux("dram_pll_ref_sel", base + 0x50, 0, 2, pll_ref_sels, ARRAY_SIZE(pll_ref_sels));
> > >       hws[IMX8MN_GPU_PLL_REF_SEL] = imx_clk_hw_mux("gpu_pll_ref_sel", base + 0x64, 0, 2, pll_ref_sels, ARRAY_SIZE(pll_ref_sels));
> > > -     hws[IMX8MN_VPU_PLL_REF_SEL] = imx_clk_hw_mux("vpu_pll_ref_sel", base + 0x74, 0, 2, pll_ref_sels, ARRAY_SIZE(pll_ref_sels));
> > > +     hws[IMX8MN_M7_ALT_PLL_REF_SEL] = imx_clk_hw_mux("m7_alt_pll_ref_sel", base + 0x74, 0, 2, pll_ref_sels, ARRAY_SIZE(pll_ref_sels));
> > >       hws[IMX8MN_ARM_PLL_REF_SEL] = imx_clk_hw_mux("arm_pll_ref_sel", base + 0x84, 0, 2, pll_ref_sels, ARRAY_SIZE(pll_ref_sels));
> > >       hws[IMX8MN_SYS_PLL3_REF_SEL] = imx_clk_hw_mux("sys_pll3_ref_sel", base + 0x114, 0, 2, pll_ref_sels, ARRAY_SIZE(pll_ref_sels));
> > >
> > > @@ -361,7 +361,7 @@ static int imx8mn_clocks_probe(struct platform_device *pdev)
> > >       hws[IMX8MN_VIDEO_PLL1] = imx_clk_hw_pll14xx("video_pll1", "video_pll1_ref_sel", base + 0x28, &imx_1443x_pll);
> > >       hws[IMX8MN_DRAM_PLL] = imx_clk_hw_pll14xx("dram_pll", "dram_pll_ref_sel", base + 0x50, &imx_1443x_dram_pll);
> > >       hws[IMX8MN_GPU_PLL] = imx_clk_hw_pll14xx("gpu_pll", "gpu_pll_ref_sel", base + 0x64, &imx_1416x_pll);
> > > -     hws[IMX8MN_VPU_PLL] = imx_clk_hw_pll14xx("vpu_pll", "vpu_pll_ref_sel", base + 0x74, &imx_1416x_pll);
> > > +     hws[IMX8MN_M7_ALT_PLL] = imx_clk_hw_pll14xx("m7_alt_pll", "m7_alt_pll_ref_sel", base + 0x74, &imx_1416x_pll);
> > >       hws[IMX8MN_ARM_PLL] = imx_clk_hw_pll14xx("arm_pll", "arm_pll_ref_sel", base + 0x84, &imx_1416x_pll);
> > >       hws[IMX8MN_SYS_PLL1] = imx_clk_hw_fixed("sys_pll1", 800000000);
> > >       hws[IMX8MN_SYS_PLL2] = imx_clk_hw_fixed("sys_pll2", 1000000000);
> > > @@ -373,7 +373,7 @@ static int imx8mn_clocks_probe(struct platform_device *pdev)
> > >       hws[IMX8MN_VIDEO_PLL1_BYPASS] = imx_clk_hw_mux_flags("video_pll1_bypass", base + 0x28, 16, 1, video_pll1_bypass_sels, ARRAY_SIZE(video_pll1_bypass_sels), CLK_SET_RATE_PARENT);
> > >       hws[IMX8MN_DRAM_PLL_BYPASS] = imx_clk_hw_mux_flags("dram_pll_bypass", base + 0x50, 16, 1, dram_pll_bypass_sels, ARRAY_SIZE(dram_pll_bypass_sels), CLK_SET_RATE_PARENT);
> > >       hws[IMX8MN_GPU_PLL_BYPASS] = imx_clk_hw_mux_flags("gpu_pll_bypass", base + 0x64, 28, 1, gpu_pll_bypass_sels, ARRAY_SIZE(gpu_pll_bypass_sels), CLK_SET_RATE_PARENT);
> > > -     hws[IMX8MN_VPU_PLL_BYPASS] = imx_clk_hw_mux_flags("vpu_pll_bypass", base + 0x74, 28, 1, vpu_pll_bypass_sels, ARRAY_SIZE(vpu_pll_bypass_sels), CLK_SET_RATE_PARENT);
> > > +     hws[IMX8MN_M7_ALT_PLL_BYPASS] = imx_clk_hw_mux_flags("m7_alt_pll_bypass", base + 0x74, 28, 1, m7_alt_pll_bypass_sels, ARRAY_SIZE(m7_alt_pll_bypass_sels), CLK_SET_RATE_PARENT);
> > >       hws[IMX8MN_ARM_PLL_BYPASS] = imx_clk_hw_mux_flags("arm_pll_bypass", base + 0x84, 28, 1, arm_pll_bypass_sels, ARRAY_SIZE(arm_pll_bypass_sels), CLK_SET_RATE_PARENT);
> > >       hws[IMX8MN_SYS_PLL3_BYPASS] = imx_clk_hw_mux_flags("sys_pll3_bypass", base + 0x114, 28, 1, sys_pll3_bypass_sels, ARRAY_SIZE(sys_pll3_bypass_sels), CLK_SET_RATE_PARENT);
> > >
> > > @@ -383,7 +383,7 @@ static int imx8mn_clocks_probe(struct platform_device *pdev)
> > >       hws[IMX8MN_VIDEO_PLL1_OUT] = imx_clk_hw_gate("video_pll1_out", "video_pll1_bypass", base + 0x28, 13);
> > >       hws[IMX8MN_DRAM_PLL_OUT] = imx_clk_hw_gate("dram_pll_out", "dram_pll_bypass", base + 0x50, 13);
> > >       hws[IMX8MN_GPU_PLL_OUT] = imx_clk_hw_gate("gpu_pll_out", "gpu_pll_bypass", base + 0x64, 11);
> > > -     hws[IMX8MN_VPU_PLL_OUT] = imx_clk_hw_gate("vpu_pll_out", "vpu_pll_bypass", base + 0x74, 11);
> > > +     hws[IMX8MN_M7_ALT_PLL_OUT] = imx_clk_hw_gate("m7_alt_pll_out", "m7_alt_pll_bypass", base + 0x74, 11);
> > >       hws[IMX8MN_ARM_PLL_OUT] = imx_clk_hw_gate("arm_pll_out", "arm_pll_bypass", base + 0x84, 11);
> > >       hws[IMX8MN_SYS_PLL3_OUT] = imx_clk_hw_gate("sys_pll3_out", "sys_pll3_bypass", base + 0x114, 11);
> >
> > The driver changes looking good from my pov.
> >
> > > diff --git a/include/dt-bindings/clock/imx8mn-clock.h b/include/dt-bindings/clock/imx8mn-clock.h
> > > index 07b8a282c268..f103b008a12a 100644
> > > --- a/include/dt-bindings/clock/imx8mn-clock.h
> > > +++ b/include/dt-bindings/clock/imx8mn-clock.h
> > > @@ -19,7 +19,7 @@
> > >  #define IMX8MN_VIDEO_PLL1_REF_SEL            10
> > >  #define IMX8MN_DRAM_PLL_REF_SEL                      11
> > >  #define IMX8MN_GPU_PLL_REF_SEL                       12
> > > -#define IMX8MN_VPU_PLL_REF_SEL                       13
> > > +#define IMX8MN_M7_ALT_PLL_REF_SEL            13
> >
> > If we take backward compatibility serious we can't do that since this
> > may break existing device trees. What you can do is:
> >
> > #define IMX8MN_M7_ALT_PLL_REF_SEL               13
> > #define IMX8MN_VPU_PLL_REF_SEL                  IMX8MN_M7_ALT_PLL_REF_SEL
> >
> > and add a comment that we need this for backward compatibility. Same
> > applies for the below defines.
> 
> If I run the command "git grep IMX8MN_VPU_PLL", this is the output:
> drivers/clk/imx/clk-imx8mn.c:   hws[IMX8MN_VPU_PLL_REF_SEL] =
> imx_clk_hw_mux("vpu_pll_ref_sel", base + 0x74, 0, 2, pll_ref_sels,
> ARRAY_SIZE(pll_ref_sels));
> drivers/clk/imx/clk-imx8mn.c:   hws[IMX8MN_VPU_PLL] =
> imx_clk_hw_pll14xx("vpu_pll", "vpu_pll_ref_sel", base + 0x74,
> &imx_1416x_pll);
> drivers/clk/imx/clk-imx8mn.c:   hws[IMX8MN_VPU_PLL_BYPASS] =
> imx_clk_hw_mux_flags("vpu_pll_bypass", base + 0x74, 28, 1,
> vpu_pll_bypass_sels, ARRAY_SIZE(vpu_pll_bypass_sels),
> CLK_SET_RATE_PARENT);
> drivers/clk/imx/clk-imx8mn.c:   hws[IMX8MN_VPU_PLL_OUT] =
> imx_clk_hw_gate("vpu_pll_out", "vpu_pll_bypass", base + 0x74, 11);
> include/dt-bindings/clock/imx8mn-clock.h:#define
> IMX8MN_VPU_PLL_REF_SEL                 13
> include/dt-bindings/clock/imx8mn-clock.h:#define IMX8MN_VPU_PLL
>                  23
> include/dt-bindings/clock/imx8mn-clock.h:#define IMX8MN_VPU_PLL_BYPASS
>                  33
> include/dt-bindings/clock/imx8mn-clock.h:#define IMX8MN_VPU_PLL_OUT
>                  43
> 
> No device tree comes out.
> So can we say that backwards compatibility is guaranteed or am I
> missing something ?

This depends on the maintainer POV since it is unfortunately quite usual
to not have the DTS files within the kernel repo. Also bootloaders may
use these defines.

Regards,
  Marco

> Thanks and regards,
> Dario
> 
> >
> > Regards,
> >   Marco
> >
> > >  #define IMX8MN_ARM_PLL_REF_SEL                       14
> > >  #define IMX8MN_SYS_PLL1_REF_SEL                      15
> > >  #define IMX8MN_SYS_PLL2_REF_SEL                      16
> > > @@ -29,7 +29,7 @@
> > >  #define IMX8MN_VIDEO_PLL1                    20
> > >  #define IMX8MN_DRAM_PLL                              21
> > >  #define IMX8MN_GPU_PLL                               22
> > > -#define IMX8MN_VPU_PLL                               23
> > > +#define IMX8MN_M7_ALT_PLL                    23
> > >  #define IMX8MN_ARM_PLL                               24
> > >  #define IMX8MN_SYS_PLL1                              25
> > >  #define IMX8MN_SYS_PLL2                              26
> > > @@ -39,7 +39,7 @@
> > >  #define IMX8MN_VIDEO_PLL1_BYPASS             30
> > >  #define IMX8MN_DRAM_PLL_BYPASS                       31
> > >  #define IMX8MN_GPU_PLL_BYPASS                        32
> > > -#define IMX8MN_VPU_PLL_BYPASS                        33
> > > +#define IMX8MN_M7_ALT_PLL_BYPASS             33
> > >  #define IMX8MN_ARM_PLL_BYPASS                        34
> > >  #define IMX8MN_SYS_PLL1_BYPASS                       35
> > >  #define IMX8MN_SYS_PLL2_BYPASS                       36
> > > @@ -49,7 +49,7 @@
> > >  #define IMX8MN_VIDEO_PLL1_OUT                        40
> > >  #define IMX8MN_DRAM_PLL_OUT                  41
> > >  #define IMX8MN_GPU_PLL_OUT                   42
> > > -#define IMX8MN_VPU_PLL_OUT                   43
> > > +#define IMX8MN_M7_ALT_PLL_OUT                        43
> > >  #define IMX8MN_ARM_PLL_OUT                   44
> > >  #define IMX8MN_SYS_PLL1_OUT                  45
> > >  #define IMX8MN_SYS_PLL2_OUT                  46
> > > --
> > > 2.32.0
> > >
> > >
> > >
> 
> 
> 
> -- 
> 
> Dario Binacchi
> 
> Embedded Linux Developer
> 
> dario.binacchi@amarulasolutions.com
> 
> __________________________________
> 
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