Re: [PATCH 7/8] serial: 8250/ingenic: Add support for the JZ4750/JZ4755 SoCs

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Hi Siarhei,

Le dim., oct. 16 2022 at 21:39:48 +0300, Siarhei Volkau <lis8215@xxxxxxxxx> a écrit :
чт, 13 окт. 2022 г. в 21:56, Siarhei Volkau <lis8215@xxxxxxxxx>:

 > Just disable the divider in ingenic_fixup_fdt() in

 I'll check that.

I checked that approach: serial seems to be working as expected,
but not all the time: there's a time period when the CGU driver
started but serial console driver is still early one.
In my case UART produces garbage at that period since CGU
needs to enable clock divider back: ext is 24MHz but 12MHz
required for audio codec and USB to function properly.

What I'd do, is just force-enable it to 12 MHz in ingenic_fixup_fdt(), since the programming manual basically says that 24 MHz does not work properly.

Then in the earlycon setup code hardcode the /2 divider with a big fat comment about why it's there.

Cheers,
-Paul

So I think Arnd's approach:

 the hardware should already be in a working state,
 with no need to touch it during early boot.

shall resolve the problem, although I can't check it on all supported
hardware.

BR,
Siarhei






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