linux-kernel - Re: [PATCH v3 3/3] serial: 8250_of: manage bus clock in suspend/resume

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Message-ID: <925ea396-fd60-460e-a3c2-968d0d837a61@riscstar.com>
Date: Fri, 11 Apr 2025 14:56:06 -0500
From: Alex Elder <elder@...cstar.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, dlan@...too.org,
 benjamin.larsson@...exis.eu, bastien.curutchet@...tlin.com,
 andriy.shevchenko@...ux.intel.com, u.kleine-koenig@...libre.com,
 lkundrak@...sk, devicetree@...r.kernel.org, linux-serial@...r.kernel.org,
 spacemit@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/3] serial: 8250_of: manage bus clock in
 suspend/resume

On 4/11/25 2:44 PM, Andy Shevchenko wrote:
> On Fri, Apr 11, 2025 at 10:36 PM Alex Elder <elder@...cstar.com> wrote:
>> On 4/11/25 2:30 PM, Andy Shevchenko wrote:
>>> Fri, Apr 11, 2025 at 10:44:18AM -0500, Alex Elder kirjoitti:
>>>> Save the bus clock pointer in the of_serial_info structure, and use
>>>> that to disable the bus clock on suspend and re-enable it on resume.
> 
> ...
> 
>>>>       if (!port->uartclk) {
>>>> -            struct clk *bus_clk;
>>>> -
>>>> -            bus_clk = devm_clk_get_optional_enabled(dev, "bus");
>>>> -            if (IS_ERR(bus_clk)) {
>>>> -                    ret = dev_err_probe(dev, PTR_ERR(bus_clk), "failed to get bus clock\n");
>>>> +            info->bus_clk = devm_clk_get_optional_enabled(dev, "bus");
>>>> +            if (IS_ERR(info->bus_clk)) {
>>>> +                    ret = dev_err_probe(dev, PTR_ERR(info->bus_clk),
>>>> +                                        "failed to get bus clock\n");
>>>>                       goto err_pmruntime;
>>>>               }
>>>>
>>>>               /* If the bus clock is required, core clock must be named */
>>>> -            info->clk = devm_clk_get_enabled(dev, bus_clk ? "core" : NULL);
>>>> +            info->clk = devm_clk_get_enabled(dev, info->bus_clk ? "core" : NULL);
>>>>               if (IS_ERR(info->clk)) {
>>>>                       ret = dev_err_probe(dev, PTR_ERR(info->clk), "failed to get clock\n");
>>>
>>> While the first patch against this file looks okay now, this one inherits the
>>> same problem (seems like not enought thinking about the code representation).
>>>
>>> Instead of rewritting half of the lines you just introduced (which is also a
>>> bad practice), add a one-liner that assigns a field to the local variable.
>>
>> So you want me to re-spin this again so that I use the local variable?
> 
> Yes.
> 
>> I understand what you're saying based on ease of review,
> 
> No, not only review. Here the main issue is ping-pong between patches.
> If you know ahead that these lines should be changed, do it from the
> start. But I understand the need to have separate changes for
> logically different pieces. That's why

I did do it from the start (v1 of the series).  Then I reworked
it based on your feedback and concluded there was no need for
keeping a copy of the bus clock in the of_serial_info structure.
In the interest of keeping the code simple I dropped it.

Yixun asked me to disable/enable the bus clock in suspend/resume,
so I was preparing the patches for that, when Greg informed me
he had already accepted the first two patches.  So I added this
new feature on the end.  This is the reason for this "ping pong."
I would have done it from the start in this series otherwise in v3.

Anyway, I'm sending v4 shortly.  I just have to run it through
another test.  It is indeed a much simpler change.

					-Alex

>> but this
>> is a simple patch
> 
> It doesn't matter how simple it is.
> 
>> and the change is very understandable, and the
>> code is no more or less clear when using the local variable.
> 
> See above.
> 
>>>>                       goto err_pmruntime;
> 
>