[BUG] mtk serial broken on mt7622 with 5.18.0

[Ilpo Järvinen]

On Wed, 1 Jun 2022, Frank Wunderlich wrote:

> Hi,
> 
> i get a serial console hang on booting my mt7622 bananapi r64 with 5.18.0
> 
> [    0.591802] Serial: 8250/16550 driver, 3 ports, IRQ sharing disabled
> [    0.599915] printk: console [ttyS0] disabled
> [    0.624563] 11002000.serial: ttyS0 at MMIO 0x11002000 (irq = 126,
> base_baud = 1562500) is a 16550A
> 
> git bisect points to this commit (cannot revert it alone)
> 
> 6f81fdded0d024c7d4084d434764f30bca1cd6b1 is the first bad commit
> commit 6f81fdded0d024c7d4084d434764f30bca1cd6b1
> Author: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
> Date:   Wed Apr 27 15:23:27 2022 +0200
> 
>     serial: 8250_mtk: Make sure to select the right FEATURE_SEL
> 
>     Set the FEATURE_SEL at probe time to make sure that BIT(0) is enabled:
>     this guarantees that when the port is configured as AP UART, the
>     right register layout is interpreted by the UART IP.
> 
>     Signed-off-by: AngeloGioacchino Del Regno
> <angelogioacchino.delregno at collabora.com>
>     Cc: stable <stable at vger.kernel.org>
>     Link:
> https://lore.kernel.org/r/20220427132328.228297-3-angelogioacchino.delregno@collabora.com
>     Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> 
>  drivers/tty/serial/8250/8250_mtk.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> merged by 6811a466d27b "Merge tag 'tty-5.18-rc7'"
> 
> reverted these 2 commits works for me
> e1bfdbc7daca 2022-04-27 serial: 8250_mtk: Fix register address for
> XON/XOFF character
> 6f81fdded0d0 2022-04-27 serial: 8250_mtk: Make sure to select the right
> FEATURE_SEL
> 
> have see this discussion [1], but can't manage to import mbox file to
> thunderbird yet
> 
> regards Frank
> 
> [1]
> https://lore.kernel.org/linux-arm-kernel/CAGXv+5Hx7cRwNzLWrExcFGy=MMOc3-0EbqCanv2E0G_DKXLCgg@mail.gmail.com/#t

The FEATURE_SEL change is already reverted to fix the problem but it 
didn't make into 5.18:

https://lore.kernel.org/linux-arm-kernel/Yot+xTBus04O9TUu@kroah.com/T/

-- 
 i.