Subject: Re: [PATCH v4 1/2] clk: rockchip: rk3288: Handle clock tree for rk3288w

From: Heiko Stuebner <[email-masked]>
Date: Fri, 03 Jul 2020 16:48:40 +0200

Am Freitag, 3. Juli 2020, 16:23:27 CEST schrieb Jagan Teki:
> On Fri, Jul 3, 2020 at 7:41 PM Heiko Stuebner <[email-masked]> wrote:
> >
> > Hi Jagan,
> >
> > Am Montag, 29. Juni 2020, 21:11:03 CEST schrieb Jagan Teki:
> > > On Tue, Jun 2, 2020 at 1:37 PM Mylène Josserand
> > > <[email-masked]> wrote:
> > > >
> > > > The revision rk3288w has a different clock tree about "hclk_vio"
> > > > clock, according to the BSP kernel code.
> > > >
> > > > This patch handles this difference by detecting which device-tree
> > > > we are using. If it is a "rockchip,rk3288-cru", let's register
> > > > the clock tree as it was before. If the device-tree node is
> > > > "rockchip,rk3288w-cru", we will apply the difference with this
> > > > version of this SoC.
> > > >
> > > > Noticed that this new device-tree compatible must be handled in
> > > > bootloader such as u-boot.
> > > >
> > > > Signed-off-by: Mylène Josserand <[email-masked]>
> > > > ---
> > > >  drivers/clk/rockchip/clk-rk3288.c | 20 ++++++++++++++++++--
> > > >  1 file changed, 18 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/clk/rockchip/clk-rk3288.c b/drivers/clk/rockchip/clk-rk3288.c
> > > > index cc2a177bbdbf..204976e2d0cb 100644
> > > > --- a/drivers/clk/rockchip/clk-rk3288.c
> > > > +++ b/drivers/clk/rockchip/clk-rk3288.c
> > > > @@ -425,8 +425,6 @@ static struct rockchip_clk_branch rk3288_clk_branches[] __initdata = {
> > > >         COMPOSITE(0, "aclk_vio0", mux_pll_src_cpll_gpll_usb480m_p, CLK_IGNORE_UNUSED,
> > > >                         RK3288_CLKSEL_CON(31), 6, 2, MFLAGS, 0, 5, DFLAGS,
> > > >                         RK3288_CLKGATE_CON(3), 0, GFLAGS),
> > > > -       DIV(0, "hclk_vio", "aclk_vio0", 0,
> > > > -                       RK3288_CLKSEL_CON(28), 8, 5, DFLAGS),
> > > >         COMPOSITE(0, "aclk_vio1", mux_pll_src_cpll_gpll_usb480m_p, CLK_IGNORE_UNUSED,
> > > >                         RK3288_CLKSEL_CON(31), 14, 2, MFLAGS, 8, 5, DFLAGS,
> > > >                         RK3288_CLKGATE_CON(3), 2, GFLAGS),
> > > > @@ -819,6 +817,16 @@ static struct rockchip_clk_branch rk3288_clk_branches[] __initdata = {
> > > >         INVERTER(0, "pclk_isp", "pclk_isp_in", RK3288_CLKSEL_CON(29), 3, IFLAGS),
> > > >  };
> > > >
> > > > +static struct rockchip_clk_branch rk3288w_hclkvio_branch[] __initdata = {
> > > > +       DIV(0, "hclk_vio", "aclk_vio1", 0,
> > > > +                       RK3288_CLKSEL_CON(28), 8, 5, DFLAGS),
> > > > +};
> > > > +
> > > > +static struct rockchip_clk_branch rk3288_hclkvio_branch[] __initdata = {
> > > > +       DIV(0, "hclk_vio", "aclk_vio0", 0,
> > > > +                       RK3288_CLKSEL_CON(28), 8, 5, DFLAGS),
> > > > +};
> > > > +
> > > >  static const char *const rk3288_critical_clocks[] __initconst = {
> > > >         "aclk_cpu",
> > > >         "aclk_peri",
> > > > @@ -936,6 +944,14 @@ static void __init rk3288_clk_init(struct device_node *np)
> > > >                                    RK3288_GRF_SOC_STATUS1);
> > > >         rockchip_clk_register_branches(ctx, rk3288_clk_branches,
> > > >                                   ARRAY_SIZE(rk3288_clk_branches));
> > > > +
> > > > +       if (of_device_is_compatible(np, "rockchip,rk3288w-cru"))
> > > > +               rockchip_clk_register_branches(ctx, rk3288w_hclkvio_branch,
> > > > +                                              ARRAY_SIZE(rk3288w_hclkvio_branch));
> > > > +       else
> > > > +               rockchip_clk_register_branches(ctx, rk3288_hclkvio_branch,
> > > > +                                              ARRAY_SIZE(rk3288_hclkvio_branch));
> > > > +
> > >
> > > Sorry for the late query on this. I am a bit unclear about this
> > > compatible change, does Linux expect to replace rockchip,rk3288-cru
> > > with rockchip,rk3288w-cru in bootloader if the chip is RK3288w? or
> > > append the existing cru compatible node with rockchip,rk3288w-cru?
> > > because replace new cru node make clock never probe since the
> > > CLK_OF_DECLARE checking rockchip,rk3288-cru
> >
> > I guess right now we'd expect "rockchip,rk3288w-cru", "rockchip,rk3288-cru",
> >
> > Thinking again about this, I'm wondering if we should switch to having
> > only one per variant ... like on the two rk3188 variants,
> > so declaring separate rk3288-cru and rk3288w-cru of-clks with shared
> > common code.
> 
> What if can check the root compatible instead cru compatible for revision W like
> 
> -  if (of_device_is_compatible(np, "rockchip,rk3288w-cru"))
> + if (of_device_is_compatible(np, "rockchip,rk3288w"))

you'd need to check against the root compatible.

> 
> This way we can have a single compatible update at bootloader that
> makes Linux adjust revision W chips code.
> 
> Doesn't it make sense?

The compatible describes the block and the rk3288w's cru isn't the same as
the rk3288's ... as the clock routing is different, so it should have a
different compatible value, I think.

As the DT sis supposed to be a _generic_ description of the hardware,
we don't want to cement hacks to other implementations would need to copy.

Heiko

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