Re: [PATCH 3/3] serial: 8250_dw: Add Allwinner A733 UART

[Vinicius Pedrosa]

Hi Andre,

On 10/6/26 11:46, Andre Przywara wrote:
> So I was wondering if we should refine the DLF detection instead? Only
> when the readback from 0xc0 returns some 2^n-1 value we assume DLF is
> implemented?

Thanks, that's better than a per-SoC quirk. On the A7Z, writing all ones
to 0xc0 reads back 0x19f, so the same family as your 0x9f with bit 8 on
top. A 2^n - 1 check rejects it.

With the check on the board, dlf_size is 0 and 0xc0 is still 0 after the
termios stress loop. Without it, 0xc0 reads 0xb after boot. I don't have
a UART with a real DLF to try.

v2 puts the check in its own patch and keeps the fallback, with the A733
compatible only selecting SKIP_SET_RATE. On the fallback alone the same
loop leaves 28 garbage bytes in 3000 lines.

The probe itself still writes all ones to 0xc0 before restoring it. Would
you rather skip that with a DT property, or leave it?

Thanks,
Vinicius