[PATCH 2/4] serial: s5p: Use livetree API to get "id" property

[Simon Glass]

On Tue, 21 Nov 2023 at 10:32, Sam Protsenko <semen.protsenko at linaro.org> wrote:
>
> On Mon, Nov 13, 2023 at 12:01 PM Simon Glass <sjg at chromium.org> wrote:
> > >
> > > The 'port_id' seems to be needed for ARCH_EXYNOS4 boards. Because
> > > Exynos4 doesn't have proper DM clocks, it uses 'id' property to get
> > > corresponding UART clock frequency from its mach code.
> > >
> > > Here is what's happening in the serial driver in case of Exynos4:
> > >
> > >   1. get_uart_clk(port_id) is called
> > >   2. which in turn calls exynos4_get_uart_clk(port_id)
> > >   3. which uses "port_id" value to read corresponding bits of of
> > > CLK_SRC_PERIL0 register
> > >   4. those bits are used to get corresponding PLL clock's frequency
> > >   5. which is in turn used to calculate UART clock rate
> > >   6. calculated rate is returned by get_uart_clk() to serial driver
> > >
> > > So I don't see any *easy* way we can get rid of that id property.
> > >
> > > The proper way of doing that would require converting Exynos4 clock
> > > code to CCF (enabling CONFIG_CLK_EXYNOS). Which of course also means
> > > implementing clocks in dts, akin to kernel's exynos4.dtsi. Then it'll
> > > be possible to get rid of 'id' property.
> >
> > That sounds good!
> >
> > >
> > > Maybe I'm missing something, please let me know.
> >
> > An easy way in the meantime would be to look at the compatible / reg
> > property, e.g. here is a sketch:
> >
> > static int get_id(ofnode node)
> > {
> > ulong addr = (ulong)plat->reg;
> > if (ofnode_device_is_compatible(node, "samsung,exynos4210-uart")) {
> >     return (addr >> 16) & 0xf;
> > ...
> >
> > reg = <0x13800000 0x3c>;
> > id = <0>;
> > };
> >
> > serail_1: serial at 13810000 {
> > compatible = "samsung,exynos4210-uart";
> > reg = <0x13810000 0x3c>;
> > id = <1>;
> > };
> >
> > serial_2: serial at 13820000 {
> > compatible = "samsung,exynos4210-uart";
> > reg = <0x13820000 0x3c>;
> > id = <2>;
> > };
> >
> > serial_3: serial at 13830000 {
> > compatible = "samsung,exynos4210-uart";
> > reg = <0x13830000 0x3c>;
> > id = <3>;
> > };
> >
> > serial_4: serial at 13840000 {
> > compatible = "samsung,exynos4210-uart";
> > reg = <0x13840000 0x3c>;
> > id = <4>;
> >
>
> To be honest, I'm a bit of busy right now working on U-Boot port for a
> new Exynos dev board, which I want to finalize and upstream ASAP. Do
> you think it's possible to take this one as is for now? At least it
> fixes one issue (fdtdec API and global data pointer).
>
> Thanks!

Yes, OK with me.

Reviewed-by: Simon Glass <sjg at chromium.org>