From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Hurley <peter-WaGBZJeGNqdsbIuE7sb01tBPR1lH4CV8@public.gmane.org>
Subject: Re: [PATCH v3 10/15] serial: stm32-usart: Add STM32 USART Driver
Date: Thu, 19 Mar 2015 10:58:36 -0400
Message-ID: <550AE41C.8070803@hurleysoftware.com>
References: <1426197361-19290-1-git-send-email-maxime.coquelin@st.com>	<1426197361-19290-11-git-send-email-maxime.coquelin@st.com>	<CAHp75Vd7+oLiLLuyocYh95TebtocWrRho6xNjuSUt8fYGp8npg@mail.gmail.com>	<CALszF6BWuUYRh+3rWnSQLApkAHA5dQXw=6x6D_evRtb+5B_ukA@mail.gmail.com>	<CAHp75Vdf6=z1d5+eYJ+QGTko9kkZf-oPfoWaf8FRoTdqcdWxjw@mail.gmail.com> <CALszF6A5Zu7i0hxSLTS-nfOAXmd0__jLjB=fHxK93Ex5Vbi9LA@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Return-path: <devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
In-Reply-To: <CALszF6A5Zu7i0hxSLTS-nfOAXmd0__jLjB=fHxK93Ex5Vbi9LA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
To: Maxime Coquelin <mcoquelin.stm32-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Andy Shevchenko <andy.shevchenko-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: =?UTF-8?B?VXdlIEtsZWluZS1Lw7ZuaWc=?= <u.kleine-koenig-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>, =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <afaerber-l3A5Bk7waGM@public.gmane.org>, Geert Uytterhoeven <geert-Td1EMuHUCqxL1ZNQvxDV9g@public.gmane.org>, Rob Herring <robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Philipp Zabel <p.zabel-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>, Linus Walleij <linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>, Stefan Agner <stefan-XLVq0VzYD2Y@public.gmane.org>, Peter Meerwald <pmeerw-jW+XmwGofnusTnJN9+BGXg@public.gmane.org>, Paul Bolle <pebolle-IWqWACnzNjzz+pZb47iToQ@public.gmane.org>, Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>, Pawel Moll <pawel.moll-5wv7dgnIgG8@public.gmane.org>, Mark Rutland <mark.rutland-5wv7dgnIgG8@public.gmane.org>, Ian Campbell <ijc+devicetree-KcIKpvwj1kUDXYZnReoRVg@public.gmane.org>, Kumar Gala <galak-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, Daniel Lezcano <daniel.lezcano-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, Jiri Slaby <jslaby-AlSwsSmVLrQ@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, "David S. Miller" <davem@davemlo>
List-Id: linux-api@vger.kernel.org

On 03/19/2015 09:55 AM, Maxime Coquelin wrote:
>>>>> +static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
>>>>> +                           struct ktermios *old)
[...]
>>>>> +       usardiv = (port->uartclk * 25) / (baud * 4);
>>>>> +       mantissa = (usardiv / 100) << USART_BRR_DIV_M_SHIFT;
>>>>> +       fraction = DIV_ROUND_CLOSEST((usardiv % 100) * 16, 100);
>>>>> +       if (fraction & ~USART_BRR_DIV_F_MASK) {
>>>>> +               fraction = 0;
>>>>> +               mantissa += (1 << USART_BRR_DIV_M_SHIFT);
>>>>> +       }
[...]
> Really, I would prefer keeping this fractional divider as it is
> implemented today.

You have to admit that's basically an unintelligible mess;
how would anyone ever be able to refactor and replace that with a
common divider implementation?

At the very least, please comment on the formula and format.

Regards,
Peter Hurley
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html