Received-SPF: pass (google.com: domain of linux-kernel+bounces-48055-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Date: Thu, 1 Feb 2024 13:52:07 +0200
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Rengarajan.S@microchip.com
Cc: Kumaravel.Thiagarajan@microchip.com, jiaqing.zhao@linux.intel.com,
	gregkh@linuxfoundation.org, ilpo.jarvinen@linux.intel.com,
	john.ogness@linutronix.de, tony@atomide.com,
	linux-kernel@vger.kernel.org, Tharunkumar.Pasumarthi@microchip.com,
	jirislaby@kernel.org, f.fainelli@gmail.com, tglx@linutronix.de,
	UNGLinuxDriver@microchip.com, linux-serial@vger.kernel.org
Subject: Re: [PATCH v1 tty] 8250: microchip: Add 4 Mbps support in PCI1XXXX
 UART
Message-ID: <ZbuF53TlbnD09rZA@smile.fi.intel.com>
References: <20240125100619.154873-1-rengarajan.s@microchip.com>
 <ZbZyW_g4OOkCqIxf@smile.fi.intel.com>
 <8406d8866968950b9bb2f2c01aaa92e3107a7a00.camel@microchip.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <8406d8866968950b9bb2f2c01aaa92e3107a7a00.camel@microchip.com>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo

On Tue, Jan 30, 2024 at 10:52:41AM +0000, Rengarajan.S@microchip.com wrote:
> On Sun, 2024-01-28 at 17:27 +0200, Andy Shevchenko wrote:
> > On Thu, Jan 25, 2024 at 03:36:19PM +0530, Rengarajan S wrote:

..

> > > +???? /*
> > > +????? * Microchip PCI1XXXX UART supports maximum baud rate up to 4
> > > Mbps
> > > +????? */
> > > +???? if (up->port.type == PORT_MCHP16550A)
> > > +???????????? max = 4000000;
> > 
> > No. Please refactor the way the 8250_port won't be modified.
> > 
> > Also you have a define for this constant, use it.
> 
> The current UART clk in MCHP Ports in pci1xxxx.c is set to 62.5 MHz in
> order to support fractional baud rates which enables generation of
> acceptable baud rate and lower error percentage from any available
> frequency. With 62.5 MHz the maximum supported baud rate supported as
> per serial_8250_get_baud_rate is 3.9 Mbps. In order to extend the
> support to 4 Mbps we had hardcoded the max value to 4 Mbps. Since, baud
> rate is calculated here we needed to make these changes in 8250_port
> and could not find a way to handle as part 8250_pci1xxxx. Can you let
> us know any alternatives to address this upper(max) limit? 

Update port->uartclk accordingly in your driver, see how other 8250_* drivers
do that (e.g., 8250_mid).

So, it will no go with hack in the 8250_port.

-- 
With Best Regards,
Andy Shevchenko