From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-serial@vger.kernel.org
Subject: Re: [PATCH v4 3/3] serial: 8250_dw: add fractional divisor support
Date: Wed, 11 Jul 2018 17:23:13 +0300 [thread overview]
Message-ID: <d2ba8f992c272543d689d87006e99c3bcf343605.camel@linux.intel.com> (raw)
In-Reply-To: <20180711144125.7d4e6a73@xhacker.debian>
On Wed, 2018-07-11 at 14:41 +0800, Jisheng Zhang wrote:
> On Tue, 10 Jul 2018 19:19:21 +0300 Andy Shevchenko wrote:
> > > +/*
> > > + * divisor = div(I) + div(F)
> > > + * "I" means integer, "F" means fractional
> > > + * quot = div(I) = clk / (16 * baud)
> > > + * frac = div(F) * 2^dlf_size
> > > + *
> > > + * let rem = clk % (16 * baud)
> > > + * we have: div(F) * (16 * baud) = rem
> > > + * so frac = 2^dlf_size * rem / (16 * baud) = (rem << dlf_size) /
> > > (16
> > > * baud)
> > > + */
> > > + quot = p->uartclk / (16 * baud);
> > > + rem = p->uartclk % (16 * baud);
> > > + *frac = DIV_ROUND_CLOSEST(rem << d->dlf_size, 16 * baud
> My python coding skill is limited. So I wrote a simple c program to
> do the check for common clks and baudrate combination. All passed. I
> paste the code here:
>
OK, I wrote test case in Python:
https://gist.github.com/andy-shev/5e980f1d752617ba814725248556ac19
Looks good to me.
Please, send v6 and assume my Reviewed-by for entire series.
--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy
next prev parent reply other threads:[~2018-07-11 14:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-10 3:09 [PATCH v4 0/3] serial: 8250_dw: add fractional divisor support Jisheng Zhang
2018-07-10 3:12 ` [PATCH v4 1/3] serial: 8250: introduce get_divisor() and set_divisor() hook Jisheng Zhang
2018-07-10 3:13 ` [PATCH v4 2/3] serial: 8250: export serial8250_do_set_divisor() Jisheng Zhang
2018-07-10 13:56 ` Andy Shevchenko
2018-07-10 3:15 ` [PATCH v4 3/3] serial: 8250_dw: add fractional divisor support Jisheng Zhang
2018-07-10 16:19 ` Andy Shevchenko
2018-07-11 6:41 ` Jisheng Zhang
2018-07-11 14:23 ` Andy Shevchenko [this message]
2018-07-11 7:11 ` [PATCH v5 " Jisheng Zhang
2018-07-11 11:31 ` Andy Shevchenko
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