linux-kernel - Re: [PATCH V6 0/5] Use CCF to describe the UART baud rate clock

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Date:   Thu, 20 Jan 2022 16:43:05 +0800
From:   Yu Tu <yu.tu@...ogic.com>
To:     Kevin Hilman <khilman@...libre.com>,
        <linux-serial@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Subject: Re: [PATCH V6 0/5] Use CCF to describe the UART baud rate clock

Hi Kevin,
	Thank you very much for your reply.

On 2022/1/20 6:37, Kevin Hilman wrote:
> [ EXTERNAL EMAIL ]
> 
> Hello,
> 
> Yu Tu <yu.tu@...ogic.com> writes:
> 
>> Using the common Clock code to describe the UART baud rate
>> clock makes it easier for the UART driver to be compatible
>> with the baud rate requirements of the UART IP on different
>> meson chips. Add Meson S4 SoC compatible.
> 
> Could you describe how this was tested and on which SoCs?  There seem to
> be some changes in this series that might affect previous SoCs.
> 
For me, the board starts normally and prints. My intention was to add 
the S4 SOC UART compatible, but for the S4 our baud rate clock is 
calculated at 12MHz by default.So a series of changes were made at your 
suggestion.

Since most SoCs are too old, I was able to find all the platforms myself 
such as Meson6, Meson8, Meson8b, GXL and so on. I only tested it with 
G12A and S4.But when I talked to Martin earlier he tried meson8b's log.
The test patch is in the attachment.

I have found that on some boards with this change, the initcall_debug 
Uart driver takes longer to initialize. Running the stty command to 
change the baud rate at the same time may cause a jam.

I'd love to know what else you suggest.

> Thanks,
> 
> Kevin
> 
> 
View attachment "g12a-clk-debug-output" of type "text/plain" (1105 bytes)

View attachment "clk-debug-output.txt" of type "text/plain" (1702 bytes)

View attachment "s4-clk-debug-output" of type "text/plain" (1104 bytes)