linux-kernel - Re: [PATCH v2] serial: 8250_mtk: correct max baud rate in set

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Message-ID: <25e098b2-d786-437c-ad92-eccb90b148f7@omp.ru>
Date: Tue, 14 Oct 2025 19:50:16 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: Fedor Pchelkin <pchelkin@...ras.ru>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby
	<jirislaby@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	<linux-serial@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>,
	<lvc-project@...uxtesting.org>, Eddie Huang <eddie.huang@...iatek.com>, Long
 Cheng <long.cheng@...iatek.com>
Subject: Re: [PATCH v2] serial: 8250_mtk: correct max baud rate in
 set_termios() method

On 10/14/25 1:07 PM, Fedor Pchelkin wrote:

>> Mediatek MT798x datasheets (that I was able to get my hands on) claim

   Thank you, Fedor, BTW! :-)

>> the maximum supported baud rate to be 3 Mbps, while commit 81bb549fdf14
>> ("serial: 8250_mtk: support big baud rate.") claimed it to be 4 Mbps --
> 
> At least MT7987A datasheet claims to support up to 4 Mbps, so I think 4 Mbps
> should be chosen for the upper limit.

   FTR, this SoC doesn't seem to be supported by the mainline kernel (looking
at Linus' repo, at least).
   I think, we should "parametrize" the max (and maybe even min?) baud rate
adding more specific compatibles to mtk8250_of_match[] (and probably setting
this parameter to 4 Mbps for the existing entry)...

> + added the authors of 81bb549fdf14 ("serial: 8250_mtk: support big baud rate.")
> to Cc.

  Just noticed that the author of this "wonderful" patch didn't even sign off
on it. "Excellent" work! :-/

> --
> Fedor

MBR, Sergey