linux-kernel - RE: [PATCH v3] clk: imx7ulp: do not export out IMX7ULP_CLK_MIPI

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Date:   Wed, 16 Oct 2019 03:18:29 +0000
From:   Fancy Fang <chen.fang@....com>
To:     Anson Huang <anson.huang@....com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>
CC:     "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH v3] clk: imx7ulp: do not export out IMX7ULP_CLK_MIPI_PLL
 clock

Hi Anson,

Please see my below comments.

Best regards,
Fancy Fang

-----Original Message-----
From: Anson Huang 
Sent: Tuesday, October 15, 2019 11:28 AM
To: Fancy Fang <chen.fang@....com>; sboyd@...nel.org; shawnguo@...nel.org
Cc: linux-clk@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; mturquette@...libre.com; s.hauer@...gutronix.de; kernel@...gutronix.de; dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH v3] clk: imx7ulp: do not export out IMX7ULP_CLK_MIPI_PLL clock

Hi, Fancy

> Subject: [PATCH v3] clk: imx7ulp: do not export out 
> IMX7ULP_CLK_MIPI_PLL clock
> 
> The mipi pll clock comes from the MIPI PHY PLL output, so it should 
> not be a fixed clock.
> 
> MIPI PHY PLL is in the MIPI DSI space, and it is used as the bit clock 
> for transferring the pixel data out and its output clock is configured 
> according to the display mode.
> 
> So it should be used only for MIPI DSI and not be exported out for 
> other usages.
> 
> Signed-off-by: Fancy Fang <chen.fang@....com>
> ---
> ChangeLog v2->v3:
>  * Keep 'IMX7ULP_CLK_MIPI_PLL' macro definition.
> 
> ChangeLog v1->v2:
>  * Keep other clock indexes unchanged as Shawn suggested.
> 
>  Documentation/devicetree/bindings/clock/imx7ulp-clock.txt | 1 -
>  drivers/clk/imx/clk-imx7ulp.c                             | 3 +--
>  2 files changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/clock/imx7ulp-clock.txt
> b/Documentation/devicetree/bindings/clock/imx7ulp-clock.txt
> index a4f8cd478f92..93d89adb7afe 100644
> --- a/Documentation/devicetree/bindings/clock/imx7ulp-clock.txt
> +++ b/Documentation/devicetree/bindings/clock/imx7ulp-clock.txt
> @@ -82,7 +82,6 @@ pcc2: pcc2@...f0000 {
>  		 <&scg1 IMX7ULP_CLK_APLL_PFD0>,
>  		 <&scg1 IMX7ULP_CLK_UPLL>,
>  		 <&scg1 IMX7ULP_CLK_SOSC_BUS_CLK>,
> -		 <&scg1 IMX7ULP_CLK_MIPI_PLL>,
>  		 <&scg1 IMX7ULP_CLK_FIRC_BUS_CLK>,
>  		 <&scg1 IMX7ULP_CLK_ROSC>,
>  		 <&scg1 IMX7ULP_CLK_SPLL_BUS_CLK>;
> diff --git a/drivers/clk/imx/clk-imx7ulp.c 
> b/drivers/clk/imx/clk-imx7ulp.c index 2022d9bead91..459b120b71d5 
> 100644
> --- a/drivers/clk/imx/clk-imx7ulp.c
> +++ b/drivers/clk/imx/clk-imx7ulp.c
> @@ -28,7 +28,7 @@ static const char * const scs_sels[]		=
> { "dummy", "sosc", "sirc", "firc", "dumm
>  static const char * const ddr_sels[]		= { "apll_pfd_sel", "upll", };
>  static const char * const nic_sels[]		= { "firc", "ddr_clk", };
>  static const char * const periph_plat_sels[]	= { "dummy", "nic1_bus_clk",
> "nic1_clk", "ddr_clk", "apll_pfd2", "apll_pfd1", "apll_pfd0", "upll", };
> -static const char * const periph_bus_sels[]	= { "dummy", "sosc_bus_clk",
> "mpll", "firc_bus_clk", "rosc", "nic1_bus_clk", "nic1_clk", 
> "spll_bus_clk", };
> +static const char * const periph_bus_sels[]	= { "dummy", "sosc_bus_clk",
> "dummy", "firc_bus_clk", "rosc", "nic1_bus_clk", "nic1_clk", 
> "spll_bus_clk", };

The reference manual does have mpll as clock option, so do you mean it will NOT be supported anymore, is mpll used inside MIPI PHY?

[FF] Yes. The mpll comes from the MIPI PHY PLL which is an internal PLL clock in MIPI space. And besides, this clock frequency can be changed or disabled dynamically when you change display mode or disable display. So it should not be used as other peripherals's root clock. This is why I want to hide this mpll from other peripherals to make things easier to be handled.

Anson

>  static const char * const arm_sels[]		= { "divcore", "dummy",
> "dummy", "hsrun_divcore", };
> 
>  /* used by sosc/sirc/firc/ddr/spll/apll dividers */ @@ -75,7 +75,6 @@ 
> static void __init imx7ulp_clk_scg1_init(struct device_node *np)
>  	clks[IMX7ULP_CLK_SOSC]		=
> imx_obtain_fixed_clk_hw(np, "sosc");
>  	clks[IMX7ULP_CLK_SIRC]		=
> imx_obtain_fixed_clk_hw(np, "sirc");
>  	clks[IMX7ULP_CLK_FIRC]		=
> imx_obtain_fixed_clk_hw(np, "firc");
> -	clks[IMX7ULP_CLK_MIPI_PLL]	= imx_obtain_fixed_clk_hw(np,
> "mpll");
>  	clks[IMX7ULP_CLK_UPLL]		=
> imx_obtain_fixed_clk_hw(np, "upll");
> 
>  	/* SCG1 */
> --
> 2.17.1