linux-kernel - Re: [PATCH] spi: rockchip: Avoid redundant clock disable in pm operation

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Message-ID: <27302919-5bcd-4bcd-bdad-02aa48e628e9@rock-chips.com>
Date: Tue, 27 Aug 2024 09:32:52 +0800
From: Jon Lin <jon.lin@...k-chips.com>
To: Brian Norris <briannorris@...omium.org>
Cc: broonie@...nel.org, linux-rockchip@...ts.infradead.org,
 linux-kernel@...r.kernel.org, heiko@...ech.de,
 linux-arm-kernel@...ts.infradead.org, linux-spi@...r.kernel.org
Subject: Re: [PATCH] spi: rockchip: Avoid redundant clock disable in pm
 operation

On 2024/8/27 6:27, Brian Norris wrote:
> (NB: I have several nearly identical copies of this email. I'm replying
> to the latest one I see.)
> 
> Hi Jon,
> 
> On Sun, Aug 25, 2024 at 11:54:22AM +0800, Jon Lin wrote:
>> Fix WARN_ON:
>> [   22.869352][ T1885] clk_spi0 already unprepared
>> [   22.869379][ T1885] WARNING: CPU: 3 PID: 1885 at drivers/clk/clk.c:813 clk_core_unprepare+0xbc4
>> [   22.869380][ T1885] Modules linked in: bcmdhd dhd_static_buf
>> [   22.869391][ T1885] CPU: 3 PID: 1885 Comm: Binder:355_2 Tainted: G        W         5.10.66 #59
>> [   22.869393][ T1885] Hardware name: Rockchip RK3588 EVB1 LP4 V10 Board (DT)
>> [   22.869397][ T1885] pstate: 60400009 (nZCv daif +PAN -UAO -TCO BTYPE=--)
>> [   22.869401][ T1885] pc : clk_core_unprepare+0xbc/0x214
>> [   22.869404][ T1885] lr : clk_core_unprepare+0xbc/0x214
> 
> I appreciate the snippet of a WARNING trace, but I'd also appreciate
> some actual explanation of what the problem is, and why you're solving
> it this way.
> 

Thank you for the reminder.

>> Fixes: e882575efc77 ("spi: rockchip: Suspend and resume the bus during NOIRQ_SYSTEM_SLEEP_PM ops")
>> Signed-off-by: Jon Lin <jon.lin@...k-chips.com>
>> ---
>>
>>   drivers/spi/spi-rockchip.c | 57 +++++++++++++++++---------------------
>>   1 file changed, 26 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
>> index e1ecd96c7858..043a7739c330 100644
>> --- a/drivers/spi/spi-rockchip.c
>> +++ b/drivers/spi/spi-rockchip.c
> 
>> +#ifdef CONFIG_PM_SLEEP
>> +static int rockchip_spi_suspend(struct device *dev)
>>   {
>> +	int ret;
>>   	struct spi_controller *ctlr = dev_get_drvdata(dev);
>> -	struct rockchip_spi *rs = spi_controller_get_devdata(ctlr);
>>   
>> -	clk_disable_unprepare(rs->spiclk);
>> -	clk_disable_unprepare(rs->apb_pclk);
>> +	ret = spi_controller_suspend(ctlr);
>> +	if (ret < 0)
>> +		return ret;
>> +
>> +	/* Avoid redundant clock disable */
>> +	if (!pm_runtime_status_suspended(dev))
>> +		rockchip_spi_runtime_suspend(dev);
> 
> It seems like you'd really be served well by
> pm_runtime_force_{suspend,resume}() here, and in fact, that's what this
> driver used to use before the breaking change (commit
> e882575efc77). Why aren't you just going back to using it? (This is the
> kind of thing I might expect in your commit message -- reasoning as to
> why you're doing what you're doing.)
> 
> And in fact, I already submitted a patch that resolves the above problem
> and does exactly that:
> 
> https://lore.kernel.org/all/20240823214235.1718769-1-briannorris@chromium.org/
> [PATCH] spi: rockchip: Resolve unbalanced runtime PM / system PM handling
> 
> Do you see any problem with it?
> 

I have reviewed your submission and although the code has been 
simplified, the execution efficiency has decreased. So although it is a 
commonly used processing solution for SPI Upstream, I still hope to 
retain a more efficiency approach as I submitted.

> Thanks,
> Brian
> 
>> +	pinctrl_pm_select_sleep_state(dev);
>>   
>>   	return 0;
>>   }
>