Hi James, On 11.5.2018 09:31, James Kelly wrote: > Hi Michal, > > On 11 May 2018 at 16:04, Michal Simek <michal.simek@xxxxxxxxxx> wrote: > >> Hi, >> >> On 7.5.2018 03:20, James Kelly wrote: >>> Add a description for how the Xilinx Clocking Wizard IP works to guide >>> subsequent patches. >>> >>> Signed-off-by: James Kelly <jamespeterkelly@xxxxxxxxx> >>> --- >>> .../clocking-wizard/clk-xlnx-clock-wizard.c | 52 >> ++++++++++++++++++++++ >>> 1 file changed, 52 insertions(+) >>> >>> diff --git a/drivers/staging/clocking-wizard/clk-xlnx-clock-wizard.c >> b/drivers/staging/clocking-wizard/clk-xlnx-clock-wizard.c >>> index cae7e6e695b0..babbed42f96d 100644 >>> --- a/drivers/staging/clocking-wizard/clk-xlnx-clock-wizard.c >>> +++ b/drivers/staging/clocking-wizard/clk-xlnx-clock-wizard.c >>> @@ -5,6 +5,58 @@ >>> * Copyright (C) 2013 - 2014 Xilinx >>> * >>> * Sören Brinkmann <soren.brinkmann@xxxxxxxxxx> >>> + * >>> + * Principles of Operation: >>> + * >>> + * The Xilinx clocking wizard IP implements a clock complex that can be >>> + * modelled as a collection of dividers and a PLL multiplier arranged in >>> + * the following configuration: >>> + * >>> + * +-------------------------------> clk_fbout >>> + * | >>> + * fin +-----+ | +-----+ vco +-----+ >>> + * clk_in1 ----->| DIV |---+--->| PLL |---+--->| DIV |-----> clk_out1 >>> + * +-----+ pfd +-----+ | +-----+ >>> + * | >>> + * | +-----+ >>> + * +--->| DIV |-----> clk_out2 >>> + * | +-----+ >>> + * | >>> + * | ... >>> + * | +-----+ >>> + * +--->| DIV |-----> clk_outn >>> + * +-----+ >>> + * >>> + * Each divider and the PLL multiplier correspond to a distinct common >>> + * clock framework struct clk. >>> + * >>> + * The number of clock outputs depends the clock primitive type (MMCM >> or PLL) >>> + * and FPGA family and can range from 2 to 7, not including clk_fbout. >>> + * Xilinx documentation is inconsistent in the numbering of these >> outputs. >>> + * The clocking wizard uses 1 thru n whereas the clocking primitives >> wrapped >>> + * by the wizard use 0 through n-1. >>> + * >>> + * This driver publishes the n output clocks in the device tree using >> addresses >>> + * 0 through n-1. The remaining two clocks (DIV and PLL) are not >> published in >>> + * the device tree but can be obtained using calls to clk_get_parent on >> one >>> + * of the output clocks. >>> + * >>> + * There are constraints on the input rate (fin), phase-frequency >>> + * detector rate (pfd), the voltage controlled oscillator rate (vco) >>> + * and output clock rates. These depend on FPGA family, clock primitive >> type >>> + * and chip speed grade. >>> + * >>> + * The available ratios for the dividers and PLL multiplier depend on >>> + * FPGA family and clock primitive type. MMCM primitves support >> fractional >>> + * ratios for the PLL multipler and first output divider, whereas PLL >>> + * primitives do not. Fractional ratios have a resolution of 0.125 >> (1/8) or 3 >>> + * fractional bits. >>> + * >>> + * Clock ratios can be dynamically changed via two different register >>> + * interfaces depending on how the "Write to DRP" configuration option >> is set >>> + * when the clocking wizard IP is customized. This driver requires that >>> + * the "Write to DRP" configuration option is disabled in customization >>> + * as it currently uses the higher-level of the two register interfaces. >>> */ >>> >>> #include <linux/platform_device.h> >>> >> >> There are some double spaces in the text without any reason. >> >> >> Thanks, >> Michal >> >> > Thanks for the feedback. > > Actually they are there for a reason ... back when I learned to type on > typewriters > it was normal to use double spaces between sentences. I sometimes fall > back into > that habit when using monospace fonts because I am used to that look. > > However, I'm happy to change to the modern convention as it would appear the > the world has moved on - at least according to Wikipedia: > https://en.wikipedia.org/wiki/Sentence_spacing. > > Will be fixed in version 2. I am not a person to judge what's the right style because I am not native speaker. But I am parsing all double spaces and spaces before/after tabs because this is quite common issue that people have incorrect editor setting. Thanks, Michal _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
