[linux-sunxi] Re: [PATCH 05/15] drm/sun4i: Add TCON TOP driver

Jernej Škrabec
2018-05-24T20:33:58Z

Hi,

Dne ?etrtek, 24. maj 2018 ob 10:43:51 CEST je Maxime Ripard napisal(a):
> Hi,
>
> On Mon, May 21, 2018 at 05:15:15PM +0200, Jernej ?krabec wrote:
> > > > + /*
> > > > + * Default register values might have some reserved bits set,
which
> > > > + * prevents TCON TOP from working properly. Set them to 0 here.
> > > > + */
> > > > + writel(0, tcon_top->regs + TCON_TOP_PORT_SEL_REG);
> > > > + writel(0, tcon_top->regs + TCON_TOP_GATE_SRC_REG);
> > > > +
> > > > + for (i = 0; i < CLK_NUM; i++) {
> > > > + const char *parent_name = "bus-tcon-top";
> > >
> > > I guess retrieving the parent's clock name at runtime would be more
> > > flexible.
> >
> > It is, but will it ever be anything else?
>
> Probably not, but when the complexity is exactly the same (using
> __clk_get_name), we'd better use the more appropriate solution. If we
> ever need to change that clock name, or to use the driver with an SoC
> that wouldn't have the same clock name for whatever reason, it will
> just work.
>
> > > > + struct clk_init_data init;
> > > > + struct clk_gate *gate;
> > > > +
> > > > + gate = devm_kzalloc(dev, sizeof(*gate), GFP_KERNEL);
> > > > + if (!gate) {
> > > > + ret = -ENOMEM;
> > > > + goto err_disable_clock;
> > > > + }
> > > > +
> > > > + init.name = gates[i].name;
> > > > + init.ops = &clk_gate_ops;
> > > > + init.flags = CLK_IS_BASIC;
> > > > + init.parent_names = &parent_name;
> > > > + init.num_parents = 1;
> > > > +
> > > > + gate->reg = tcon_top->regs + TCON_TOP_GATE_SRC_REG;
> > > > + gate->bit_idx = gates[i].bit;
> > > > + gate->lock = &tcon_top->reg_lock;
> > > > + gate->hw.init = &init;
> > > > +
> > > > + ret = devm_clk_hw_register(dev, &gate->hw);
> > > > + if (ret)
> > > > + goto err_disable_clock;
> > >
> > > Isn't it what clk_hw_register_gate is doing?
> >
> > Almost, but not exactly. My goal was to use devm_* functions, so there is
> > no need to do any special cleanup.
>
> Is it the only difference? If so, you can just create a
> devm_clk_hw_register gate.

I checked around and it seems that in clk core there are only non devm_*
helpers like clk_hw_register_gate() for some reason. I guess I'll just use
that and manually unregister all the clocks in cleanup function.

Best regards,
Jernej