Hi Milind, On 03/09/2020 09:22, Milind Parab wrote: > Also, note that CDNS MHDP implements DP_FRAMER_TU_p where bits 5:0 is tu_valid_symbols. So max programmable value is 63. > Register document gives following explanation > "Number of valid symbols per Transfer Unit (TU). Rounded down to lower integer value (Allowed values are 1 to (TU_size-1)" > > So, it says in case vs calculates to 64 (where Avail BW and Req BW are same) we program tu_valid_symbols = 63 Hmm, so "Rounded down to lower integer value" means floor(x) - 1 ? If that's the case, we need to subtract 1 in all cases, not only when req bw == avail bw. > Third, is about the line_threshold calculation > Unlike TU_SIZE and Valid_Symbols, line_threshold is implementation dependent > > CDNS MHDP register specs gives the definition as " Video FIFO latency threshold" > Bits 5:0, Name "cfg_active_line_tresh", Description "Video Fifo Latency threshold. Defines the number of FIFO rows before reading starts. This setting depends on the transmitted video format and link rate." > > This parameter is the Threshold of the FIFO. For optimal performance (considering equal write and read clock) we normally put the threshold in the mid of the FIFO. > Hence the reset value is fixed as 32. > Since symbol FIFO is accessed by Pxl clock and Symbol Link Clock the Threshold is set to a value which is dependent on the ratio of these clocks > > line_threshold = full_fifo - fifo_ratio_due_to_clock_diff + 2 > where, > full_fifo = (vs+1) * (8/bpp) > fifo_ratio_due_to_clock_diff = ((vs+1) * pxlclock/mhdp->link.rate - 1) / mhdp->link.num_lanes > > Note that line_threshold can take a max value of 63 That doesn't result in anything sensible. 8/bpp is always 0. Tomi -- Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
