Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.34 as permitted sender) client-ip=23.128.96.34;
Message-ID: <1431f5b4-fb39-483b-9314-ed2b7c118c11@gmail.com>
Date:   Wed, 4 Oct 2023 20:44:36 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v12 1/1] serial: core: Start managing serial controllers
 to enable runtime PM
Content-Language: en-US
To:     Tony Lindgren <tony@atomide.com>, Johan Hovold <johan@kernel.org>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Andy Shevchenko <andriy.shevchenko@intel.com>,
        Dhruva Gole <d-gole@ti.com>,
        =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
        John Ogness <john.ogness@linutronix.de>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        linux-omap@vger.kernel.org,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
References: <20230525113034.46880-1-tony@atomide.com>
 <62d3678a-a23d-4619-95de-145026629ba8@gmail.com>
 <20231003121455.GB34982@atomide.com> <20231003122137.GC34982@atomide.com>
 <dc7af79d-bca8-4967-80fe-e90907204932@gmail.com>
 <20231004061708.GD34982@atomide.com> <ZR0Q7YUwgQV5TLhQ@hovoldconsulting.com>
 <20231004090320.GE34982@atomide.com> <ZR0s7dEh19lTid6-@hovoldconsulting.com>
 <20231004100123.GH34982@atomide.com>
From:   Maximilian Luz <luzmaximilian@gmail.com>
In-Reply-To: <20231004100123.GH34982@atomide.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 10/4/23 12:01, Tony Lindgren wrote:
> * Johan Hovold <johan@kernel.org> [231004 09:14]:
>> On Wed, Oct 04, 2023 at 12:03:20PM +0300, Tony Lindgren wrote:
>>> The serial port device and serdev device are siblings of the physical
>>> serial port controller device as seen in the hierarcy printed out by
>>> Maximilian.
>>
>> Yeah, and that's precisely the broken part. Keeping the serdev
>> controller active is supposed to keep the serial controller active. Your
>> serial core rework appears to have broken just that.
> 
> Hmm OK good point, tx can currently have an extra delay if a serdev
> device is active, and the serial port controller device is not active.
> 
> So we can check for active port->dev instead of &port_dev->dev though
> to know when when start_tx() is safe to do as below.

I can confirm that this works as well.

Thanks,
Max

> 8< -----------------
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 6207f0051f23d..defecc5b04422 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -156,7 +156,7 @@ static void __uart_start(struct uart_state *state)
>   	 * enabled, serial_port_runtime_resume() calls start_tx() again
>   	 * after enabling the device.
>   	 */
> -	if (pm_runtime_active(&port_dev->dev))
> +	if (!pm_runtime_enabled(port->dev) || pm_runtime_active(port->dev))
>   		port->ops->start_tx(port);
>   	pm_runtime_mark_last_busy(&port_dev->dev);
>   	pm_runtime_put_autosuspend(&port_dev->dev);
>