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

[Lukasz Majewski <lukma@denx.de>]

On Wed, 8 May 2019 07:45:39 +0000
Peng Fan <peng.fan@nxp.com> wrote:

> > -----Original Message-----
> > From: Lukasz Majewski [mailto:lukma at denx.de]
> > Sent: 2019年5月8日 15:40
> > To: Peng Fan <peng.fan@nxp.com>
> > Cc: sbabic at denx.de; festevam at gmail.com; dl-uboot-imx
> > <uboot-imx@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@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@nxp.com>
> > > > Cc: sbabic at denx.de; festevam at gmail.com; dl-uboot-imx
> > > > <uboot-imx@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@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@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.

Ok.

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

My point is that this driver pollutes the fixed-clock code and makes it
imx8 specific.

> 
> 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.

So this code is for fixing bugs (incomplete initialisation) in SoC's
ROM?

> 
> 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  




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
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