On Wed, 2012-02-15 at 14:55 +0530, K, Mythri P wrote: > Hi, > > On Wed, Feb 15, 2012 at 1:11 PM, Tomi Valkeinen <tomi.valkeinen@xxxxxx> wrote: > > On Wed, 2012-02-15 at 11:20 +0530, mythripk@xxxxxx wrote: > >> From: Mythri P K <mythripk@xxxxxx> > >> > >> Add M2 divider in the equation to calculate regm and regmf. > >> Formula for calculating: > >> Output clock on digital core domain: > >> CLKOUT = (M / (N+1))*CLKINP*(1/M2) > >> Internal oscillator output clock on internal LDO domain: > >> CLKDCOLDO = (M / (N+1))*CLKINP > >> The current code when allows variable M2 values as input > >> ignores using M2 divider values in calculation of regm and regmf. > >> so fix it by using M2 in calculation although the default value for > >> M2 is 1. > >> > >> Signed-off-by: Mythri P K <mythripk@xxxxxx> > >> --- > >> drivers/video/omap2/dss/hdmi.c | 16 ++++++++-------- > >> 1 files changed, 8 insertions(+), 8 deletions(-) > >> > >> diff --git a/drivers/video/omap2/dss/hdmi.c b/drivers/video/omap2/dss/hdmi.c > >> index 92a6679..9185630 100644 > >> --- a/drivers/video/omap2/dss/hdmi.c > >> +++ b/drivers/video/omap2/dss/hdmi.c > >> @@ -256,24 +256,24 @@ static void hdmi_compute_pll(struct omap_dss_device *dssdev, int phy, > >> > >> refclk = clkin / pi->regn; > >> > >> - /* > >> - * multiplier is pixel_clk/ref_clk > >> - * Multiplying by 100 to avoid fractional part removal > >> - */ > >> - pi->regm = (phy * 100 / (refclk)) / 100; > >> - > >> if (dssdev->clocks.hdmi.regm2 == 0) > >> pi->regm2 = HDMI_DEFAULT_REGM2; > >> else > >> pi->regm2 = dssdev->clocks.hdmi.regm2; > >> > >> /* > >> + * multiplier is pixel_clk/ref_clk > >> + * Multiplying by 100 to avoid fractional part removal > >> + */ > >> + pi->regm = (phy * 100 * pi->regm2 / (refclk)) / 100; > > > > No need for parenthesis around refclk. > Well this is just a copy of old code will change. The multiplication and division with 100 is actually extra also, they don't bring any precision here. > > > >> + > >> + /* > >> * fractional multiplier is remainder of the difference between > >> * multiplier and actual phy(required pixel clock thus should be > >> * multiplied by 2^18(262144) divided by the reference clock > >> */ > >> - mf = (phy - pi->regm * refclk) * 262144; > >> - pi->regmf = mf / (refclk); > >> + mf = (phy - pi->regm / pi->regm2 * refclk) * 262144; > > > > What kind of values does regm have? If the regm2 is something else than > > 1, and regm is relatively small value, it's quite easy to lose precision > > there. Would it be better to have: > Normally regm values are much higher compared to regm2 , regm2 is > normally 1 or 2. > also given that regm2 is a multiplier factor in calculating regm there > should not be any precision factor what do you think ? Ok, I think it's fine. Tomi
Attachment:
signature.asc
Description: This is a digitally signed message part
