Re: [PATCH v2 3/3] spi: meson-axg: add a linear clock divider support

[Sunny Luo]

Hi Jerome,

On 2018/12/13 17:28, Jerome Brunet wrote:
> On Thu, 2018-12-13 at 09:55 +0100, Neil Armstrong wrote:

> > > diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> > >   config SPI_MESON_SPICC
> > >   	tristate "Amlogic Meson SPICC controller"
> > > -	depends on ARCH_MESON || COMPILE_TEST
> > > +	depends on OF && COMMON_CLK && (ARCH_MESON || COMPILE_TEST)
>
> The purpose of this patch is clock, right ? Why does it add a dependency on OF
> ?
> I did it by the way. Maybe it's better to add it in patch 1.


> > > +static int meson_spicc_clk_init(struct meson_spicc_device *spicc)
> > > +{
> > > +	struct device *dev = &spicc->pdev->dev;
> > > +	struct clk_fixed_factor *div0;
> > > +	struct clk_divider *div1;
>
> Could you come up with something better than div0 and div1 ? it is confusing,
> especially with the comment above about div3 and 4 ... fixed_factor, div maybe
> ?
> Good, It is really confusing, I will change next patch.


> > > +	div1 = &meson_spicc_div1;
> > > +	div1->reg = spicc->base + (u64)div1->reg;
>
> So you have static data which you override here. This works only if there is a
> single instance ... and does not really improve readability in your case.
>
> IMO, you'd be better off without the static data above.

This is a terrible bug for more than one instances. I must overwrite it.


> > > +	if (!spicc->data->has_enhance_clk_div) {
>
> Do all SoC with 'has_oen' have 'has_enhance_clk_div' too ?
> DO you really need two flags ?

Yes, all Soc with 'has_oen' must have 'has_enhance_clk_div' too.
It is distinct to use two flags here, what do you think of it?

> > > +	mux = &meson_spicc_sel;
> > > +	snprintf(name, sizeof(name), "%s#_sel", dev_name(dev));
> > > +	init.name = name;
> > > +	init.ops = &clk_mux_ops;
> > > +	init.parent_names = mux_parent_names;
> > > +	init.num_parents = 2;
> > > +	init.flags = CLK_SET_RATE_PARENT | CLK_SET_RATE_NO_REPARENT;
>
> Why CLK_SET_RATE_NO_REPARENT ? CCF should pick the parent that give the best
> results, best to let it do its task ...
There are two div in AXG, one is the coarse old-div and the other is 
enhance-div. From SoCs designer's opinion, the ehance-div aims to take 
place of the old-div.