[PATCH v1 06/16] clk: starfive: Add JH8100 System clock generator driver

[Emil Renner Berthing]

JeeHeng Sia wrote:
> > -----Original Message-----
> > From: Emil Renner Berthing <emil.renner.berthing at canonical.com>
> > Sent: Saturday, December 9, 2023 12:25 AM
> > To: JeeHeng Sia <jeeheng.sia at starfivetech.com>; kernel at esmil.dk; conor at kernel.org; robh+dt at kernel.org;
> > krzysztof.kozlowski+dt at linaro.org; paul.walmsley at sifive.com; palmer at dabbelt.com; aou at eecs.berkeley.edu;
> > mturquette at baylibre.com; sboyd at kernel.org; p.zabel at pengutronix.de; emil.renner.berthing at canonical.com; Hal Feng
> > <hal.feng at starfivetech.com>; Xingyu Wu <xingyu.wu at starfivetech.com>
> > Cc: linux-riscv at lists.infradead.org; devicetree at vger.kernel.org; linux-kernel at vger.kernel.org; linux-clk at vger.kernel.org; Leyfoon Tan
> > <leyfoon.tan at starfivetech.com>
> > Subject: Re: [PATCH v1 06/16] clk: starfive: Add JH8100 System clock generator driver
> >
> > Sia Jee Heng wrote:
> > > Add support for JH8100 System clock generator.
> > >
> > > Signed-off-by: Sia Jee Heng <jeeheng.sia at starfivetech.com>
> > > Reviewed-by: Ley Foon Tan <leyfoon.tan at starfivetech.com>
> > > ---
> > >  MAINTAINERS                                   |   8 +
> > >  drivers/clk/starfive/Kconfig                  |   9 +
> > >  drivers/clk/starfive/Makefile                 |   1 +
> > >  drivers/clk/starfive/clk-starfive-common.h    |   9 +-
> > >  drivers/clk/starfive/jh8100/Makefile          |   3 +
> > >  .../clk/starfive/jh8100/clk-starfive-jh8100.h |  11 +
> > >  drivers/clk/starfive/jh8100/clk-sys.c         | 455 ++++++++++++++++++
> > >  7 files changed, 495 insertions(+), 1 deletion(-)
> > >  create mode 100644 drivers/clk/starfive/jh8100/Makefile
> > >  create mode 100644 drivers/clk/starfive/jh8100/clk-starfive-jh8100.h
> > >  create mode 100644 drivers/clk/starfive/jh8100/clk-sys.c
...
> > > diff --git a/drivers/clk/starfive/Makefile b/drivers/clk/starfive/Makefile
> > > index 012f7ee83f8e..6cb3ce823330 100644
> > > --- a/drivers/clk/starfive/Makefile
> > > +++ b/drivers/clk/starfive/Makefile
> > > @@ -10,3 +10,4 @@ obj-$(CONFIG_CLK_STARFIVE_JH7110_AON)	+= clk-starfive-jh7110-aon.o
> > >  obj-$(CONFIG_CLK_STARFIVE_JH7110_STG)	+= clk-starfive-jh7110-stg.o
> > >  obj-$(CONFIG_CLK_STARFIVE_JH7110_ISP)	+= clk-starfive-jh7110-isp.o
> > >  obj-$(CONFIG_CLK_STARFIVE_JH7110_VOUT)	+= clk-starfive-jh7110-vout.o
> > > +obj-$(CONFIG_CLK_STARFIVE_JH8100_SYS)	+= jh8100/
> >
> > I don't really see why do you need a special subdirectory for the JH8100? The
> > JH7110 drivers do fine without it.
> Each subfolder can represent a different platform, making it easier to
> locate and maintain platform-specific code. Since the code is expected
> to grow in the future, let's start organizing it in a folder-based structure
> for easier maintenance at a later stage.

Yes, but that's not what you're doing here. You're making just one of the 3
almost identical drivers be different for no good reason.

> > > diff --git a/drivers/clk/starfive/clk-starfive-common.h b/drivers/clk/starfive/clk-starfive-common.h
> > > index fed45311360c..ec30af0658cf 100644
> > > --- a/drivers/clk/starfive/clk-starfive-common.h
> > > +++ b/drivers/clk/starfive/clk-starfive-common.h
> > > @@ -103,6 +103,13 @@ struct starfive_clk_data {
> > >  	.parents = { [0] = _parent },						\
> > >  }
> > >
> > > +#define STARFIVE_GINV(_idx, _name, _flags, _parent)[_idx] = {			\
> > > +	.name = _name,								\
> > > +	.flags = _flags,							\
> > > +	.max = STARFIVE_CLK_ENABLE | STARFIVE_CLK_INVERT,			\
> > > +	.parents = { [0] = _parent },						\
> > > +}
> > > +
> > >  struct starfive_clk {
> > >  	struct clk_hw hw;
> > >  	unsigned int idx;
> > > @@ -114,7 +121,7 @@ struct starfive_clk_priv {
> > >  	spinlock_t rmw_lock;
> > >  	struct device *dev;
> > >  	void __iomem *base;
> > > -	struct clk_hw *pll[3];
> > > +	struct clk_hw *pll[8];
> >
> > These extra slots are just used for fixed factor dummy PLLs right now, similar
> > to how the JH7110 first used them and later had to rework drivers and device
> > trees for the proper PLL driver.
> Yes, its intention is similar to JH8100. We will submit other clock
> domains and PLL at later stage but not so soon.
> >
> > This time around I'd much rather you work on getting the PLL driver in first,
> > so we don't need all that churn.
> I am sorry but we started development on FPGA. Unfortunately, the PLL driver
> and other domains are planned to be finished at a later stage. I have tried
> to minimize the churn as much as possible.

It's awesome that you're beginning upstreaming early, but if you don't have
this in silicon yet, how do you even know that this driver works?

If you're just using this for testing on FPGAs you can create dummy fixed
clocks in the device tree for the PLLs that this driver can consume.  Then
later when you have a PLL driver you can replace those fixed clocks with the
output of that driver.

/Emil