Date: Tue, 30 Jun 2015 08:44:29 -0700 From: Leonardo Fogel <leonardofogel@yahoo.com.br> To: freebsd-arm@freebsd.org Subject: Improvement to am335x_lcd_calc_divisor() Message-ID: <1435679069.12329.YahooMailBasic@web120802.mail.ne1.yahoo.com>
next in thread | raw e-mail | index | archive | help
I just realized the last proposal would depend on 64-bit multiplication, wh= ich may not be available. Here is another approach: Let f be the fractional part of r, the real number (R%F)/F. If f >=3D 0.5, = then lround(r) rounds up. We can test the multiplicative inverse of f, 1/f,= F/(R%F). If 1/f <=3D 2, then lround(r) rounds up. =09if (freq =3D=3D 0) /* there is a bug somewhere. */ =09=09return (255); =09if ((reference%freq > 0) && (freq/(reference%freq) <=3D 2)) =09=09div =3D reference/freq + 1; /* rounds up */ =09else =09=09div =3D reference/freq; /* rounds down */ =09/* Raster mode case: divisors are in range from 2 to 255 */ =09if (div < 2) =09=09div =3D 2; =09else if (div > 255) =09=09dir =3D 255; =09return (div); Thank you. Leonardo
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1435679069.12329.YahooMailBasic>