[U-Boot] [i.MX8MM+CCF 11/41] clk: fixed_rate: export clk_fixed_rate

Wed May 8 07:45:39 UTC 2019

> -----Original Message-----
> From: Lukasz Majewski [mailto:lukma at denx.de]
> Sent: 2019年5月8日 15:40
> To: Peng Fan <peng.fan at nxp.com>
> Cc: sbabic at denx.de; festevam at gmail.com; dl-uboot-imx
> <uboot-imx at nxp.com>; sjg at chromium.org; jagan at amarulasolutions.com;
> sr at denx.de; u-boot at lists.denx.de; trini at konsulko.com
> Subject: Re: [i.MX8MM+CCF 11/41] clk: fixed_rate: export clk_fixed_rate
> 
> On Wed, 8 May 2019 06:51:46 +0000
> Peng Fan <peng.fan at nxp.com> wrote:
> 
> > > -----Original Message-----
> > > From: Lukasz Majewski [mailto:lukma at denx.de]
> > > Sent: 2019年5月8日 14:46
> > > To: Peng Fan <peng.fan at nxp.com>
> > > Cc: sbabic at denx.de; festevam at gmail.com; dl-uboot-imx
> > > <uboot-imx at nxp.com>; sjg at chromium.org;
> jagan at amarulasolutions.com;
> > > sr at denx.de; u-boot at lists.denx.de; trini at konsulko.com
> > > Subject: Re: [i.MX8MM+CCF 11/41] clk: fixed_rate: export
> > > clk_fixed_rate
> > >
> > > On Tue, 7 May 2019 13:27:45 +0000
> > > Peng Fan <peng.fan at nxp.com> wrote:
> > >
> > > > > Subject: Re: [i.MX8MM+CCF 11/41] clk: fixed_rate: export
> > > > > clk_fixed_rate
> > > > >
> > > > > Hi Peng,
> > > > >
> > > > > > Export the structure for others to use.
> > > > > >
> > > > > > Signed-off-by: Peng Fan <peng.fan at nxp.com>
> > > > > > ---
> > > > > >  drivers/clk/clk_fixed_rate.c | 8 +-------
> > > > > > include/linux/clk-provider.h | 7 +++++++
> > > > > >  2 files changed, 8 insertions(+), 7 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/clk/clk_fixed_rate.c
> > > > > > b/drivers/clk/clk_fixed_rate.c index 089f060a23..069e643fbc
> > > > > > 100644 --- a/drivers/clk/clk_fixed_rate.c
> > > > > > +++ b/drivers/clk/clk_fixed_rate.c
> > > > > > @@ -6,13 +6,7 @@
> > > > > >  #include <common.h>
> > > > > >  #include <clk-uclass.h>
> > > > > >  #include <dm.h>
> > > > > > -
> > > > > > -struct clk_fixed_rate {
> > > > > > -	struct clk clk;
> > > > > > -	unsigned long fixed_rate;
> > > > > > -};
> > > > > > -
> > > > > > -#define to_clk_fixed_rate(dev)	((struct clk_fixed_rate
> > > > > > *)dev_get_platdata(dev)) +#include <linux/clk-provider.h>
> > > > > >
> > > > > >  static ulong clk_fixed_rate_get_rate(struct clk *clk)  { diff
> > > > > > --git a/include/linux/clk-provider.h
> > > > > > b/include/linux/clk-provider.h index 3ed0db86d2..b2bed768b6
> > > > > > 100644 --- a/include/linux/clk-provider.h
> > > > > > +++ b/include/linux/clk-provider.h
> > > > > > @@ -112,6 +112,13 @@ struct clk_fixed_factor {  #define
> > > > > > to_clk_fixed_factor(_clk) container_of(_clk, struct
> > > > > > clk_fixed_factor,\ clk)
> > > > > >
> > > > > > +struct clk_fixed_rate {
> > > > > > +	struct clk clk;
> > > > > > +	unsigned long fixed_rate;
> > > > > > +};
> > > > >
> > > > > I think that this struct shall stay where it was. Moreover, the
> > > > > clk-provider.h is not the API to be used by other parts of the
> > > > > clock API.
> > > > >
> > > > > The clk_fixed_rate shall be accessed via get_rate() only and in
> > > > > IMX6Q it is available in early SPL (parsed from dts /clocks
> > > > > property
> > > > > - the 24MHz OSC)
> > > > > > +
> > > > > > +#define to_clk_fixed_rate(dev)	((struct clk_fixed_rate
> > > > > > *)dev_get_platdata(dev)) +
> > > > > >  int clk_register(struct clk *clk, const char *drv_name,
> > > > > >  		 ulong drv_data, const char *name,
> > > > > >  		 const char *parent_name);
> > > > >
> > > > > Please explain why iMX8MM needs such global export?
> > > >
> > > > In clk-imx8mm.c, first configure ARM clk to osc24M fixed clk to
> > > > change pll clock.
> > > > +       /* Configure ARM to osc24M */
> > > > +       clk_get_by_id(IMX8MM_CLK_A53_SRC, &clkp);
> > > > +       uclass_get_device_by_name(UCLASS_CLK, "clock-osc-24m",
> > > &devp);
> > > > +       clkp1 = &to_clk_fixed_rate(devp)->clk;
> > > > +       clk_set_parent(clkp, clkp1);
> > >
> > > This code looks a bit strange to me. Why imx8mm sets parent here?
> >
> > The A53 clk could not change on the fly. There is a mux here, one is
> > PLL, one is OSC, And there are others. If we want to change the pll
> > clock which is currently being used by A53, we need first switch the
> > A53 clk to source from OSC, then change pll clock, then switch A53 clk
> > back to PLL.
> 
> The above description looks like a "standard" procedure for bypassing PLL
> when it is going to be locked.
> 
> The same is also performed on IMX6Q:
> 
> https://elixir.bootlin.com/linux/v5.1/source/drivers/clk/imx/clk-imx6q.c#L88
> 
> But I've not ported that part from the original Linux source code.

i.MX8MM is different.

This is how Linux change cpu's clock.
https://elixir.bootlin.com/linux/v5.1/source/drivers/clk/imx/clk-imx8mm.c#L655

It has a new cpu clk driver, I do not want to introduce that complexity in U-Boot.

This patch is just a simplified step of the upper Linux code.

The reason to configure the clk here is that ROM not configure the clock following
datasheet even it not hurt, but better to configure it right in SPL.

Thanks,
Peng.

> 
> >
> > >
> > > In the imx6q I write "osc" as a part of the clock tree:
> > >
> > >         clk_dm(IMX6QDL_CLK_PLL2,
> > >                imx_clk_pllv3(IMX_PLLV3_GENERIC, "pll2_bus", "osc",
> > >                              base + 0x30, 0x1));
> > >
> > > And here the parent is set as "osc".
> > >
> > > Moreover, the "osc" or in your case "clock-osc-24m" shall be
> > > available in "clocks" DTS node and hence parsed / setup from there
> > > (and be available in the clk uclass list).
> > >
> > > > +
> > > > +       /* Configure ARM PLL to 1.2GHz */
> > > > +       clk_get_by_id(IMX8MM_ARM_PLL, &clkp1);
> > > > +       clk_set_rate(clkp1, 1200000000UL);
> > >
> > > Shouldn't this be set in DTS ? As it is now - it seems like a
> > > hardcoded value for early SPL clock setup. Am I right?
> >
> > You mean get freq from cpu opp and set cpu freq? I do not have good
> > idea how to set in DTS.
> 
> I'm thinking about following description of the "osc" fixed clock:
> https://elixir.bootlin.com/linux/v5.1/source/arch/arm/boot/dts/imx6qdl.dtsi#
> L64
> 
> and
> 
> http://git.denx.de/?p=u-boot/u-boot-imx.git;a=blob;f=arch/arm/dts/imx6qdl.
> dtsi;h=c0a94780087382a6e2805b7d6572f3e5e294e302;hb=HEAD#l53
> 
> The "fixed-clock" code has been adjusted to comply with the above DTS
> (which is provided in pre-reloc SPL - even before console and ddr setup).
> 
> (I had to use debug uart for debugging).
> 
> >
> > Thanks,
> > Peng.
> >
> > >
> > > > +       clk_get_by_id(IMX8MM_ARM_PLL_OUT, &clkp1);
> > > > +       clk_enable(clkp1);
> > > > +       clk_set_parent(clkp, clkp1);
> > > > +
> > > > +       /* Configure DIV to 1.2GHz */
> > > > +       clk_get_by_id(IMX8MM_CLK_A53_DIV, &clkp1);
> > > > +       clk_set_rate(clkp1, 1200000000UL);
> > > >
> > > > Regards,
> > > > Peng.
> > > >
> > > > >
> > > > >
> > > > > Best regards,
> > > > >
> > > > > Lukasz Majewski
> > > > >
> > > > > --
> > > > >
> > > > > DENX Software Engineering GmbH,      Managing Director:
> Wolfgang
> > > > > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194
> > > > > Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax:
> > > > > (+49)-8142-66989-80 Email: lukma at denx.de
> > >
> > >
> > >
> > >
> > > Best regards,
> > >
> > > Lukasz Majewski
> > >
> > > --
> > >
> > > DENX Software Engineering GmbH,      Managing Director: Wolfgang
> > > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > > lukma at denx.de
> 
> 
> 
> 
> Best regards,
> 
> Lukasz Majewski
> 
> --
> 
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> lukma at denx.de