On Tue, 2011-01-18 at 10:45 +0530, ext Taneja, Archit wrote: > Hi, > > I was going through the DSS2 code which sets up the FCLK > coming from PRCM and the DISPC divivors to get the required pixel > clock. > > The function dss_calc_clock_div() does a brute force search across > all possible values of: a) DPLL divisor whose output goes to DSS, b) > DISPC_DIVISOR.LCD, c) DISPC_DIVISOR.pcd > > The combination which gives a clock frequency closest to the > required pixel clock is chosen. > > Hence, it seems that the resultant DISPC_FCLK clock frequency doesn't > take into account the extra margin needed for downscaling: > > Req dispc_fclk >= pck * hscale_ratio * vscale_ration * K > > Do you thing putting a further constraint (like DISPC_FCLK needs to be > greater than a given value) should be a part of the calculations to > ensure successful scaling? It's been a while since I looked at the fclk requirements, but isn't the current CONFIG_OMAP2_DSS_MIN_FCK_PER_PCK enough? It is quite hackish and static, but a proper implementation is much harder (dynamically changing the clocks depending on the scaling). Or were there some additional restrictions? Tomi -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
