Received-SPF: pass (google.com: domain of linux-kernel+bounces-148120-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>
Date: Wed, 17 Apr 2024 11:18:33 +0300 (EEST)
To: Michael Pratt <mcpratt@pm.me>
cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>, 
    LKML <linux-kernel@vger.kernel.org>, 
    linux-serial <linux-serial@vger.kernel.org>, 
    Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 
    Jiri Slaby <jirislaby@kernel.org>, 
    Wander Lairson Costa <wander@redhat.com>, 
    Vamshi Gajjela <vamshigajjela@google.com>
Subject: Re: [PATCH v2 1/3] serial: core: Store fifo timeout again
In-Reply-To: <zTaajAZtS59Hv5offvbHJV1ptivBxD4WaZP_M-zQkicUtDb4mokpuKCFGIzUVL3p2yDSqHx9Uf2vIYVlbGeHN8xMJ6H3VWxwH3MPe1cH5a4=@pm.me>
Message-ID: <35bd3e50-8a60-7c0e-23a9-ae483e293a15@linux.intel.com>
References: <20240416182741.22514-1-mcpratt@pm.me> <20240416182741.22514-2-mcpratt@pm.me> <Zh7KV0FuM2B56J7w@smile.fi.intel.com> <zTaajAZtS59Hv5offvbHJV1ptivBxD4WaZP_M-zQkicUtDb4mokpuKCFGIzUVL3p2yDSqHx9Uf2vIYVlbGeHN8xMJ6H3VWxwH3MPe1cH5a4=@pm.me>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII

On Tue, 16 Apr 2024, Michael Pratt wrote:
> On Tuesday, April 16th, 2024 at 14:58, Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> 
> > > + if (port->fifosize > 1)
> > > + port->timeout = uart_fifo_timeout(port);
> > 
> > 
> > else
> > port->timeout = port->frame_time;
> > 
> 
> 
> Consistent with what I said in the other reply, the only reason that
> I have an if statement here, is to avoid doing extra math for devices
> without a fifo, as a specifically calculated timeout value would be useless
> in those cases.

Please benchmark to show this actually matters if want to make this claim. 
Otherwise just do the math always.

> However, if you don't like the 10 ms default timeout, perhaps port->frame_time
> could actually be a more reasonable default value? That is, provided 
> that we have a process 
> for calculating the proper value already in place...

While it would be a step toward the correct direction, you'd still need to 
add the safety there which is already done by uart_fifo_timeout(). So no, 
I don't think there's advantage of using port->frame_time over just 
calling uart_fifo_timeout() and ensuring uart_fifo_timeout() is always 
using at least 1 as the FIFO size when it does the calculations.

-- 
 i.