Hi Alexander, On Mon, Oct 28, 2019 at 06:05:19PM +0100, Alexander Weidinger wrote: > Hello Genodians, > > we adapted the zynq7000 target to run with Genode/seL4[4], which was > done accordingly to the imx6 and imx7 targets already existing in Genode. > > Since we are in need for a timer component and the seL4 doesn't provide > a "l4_ipc_sleep()" call, like it is used for the generic timer component > in Fiasco.OC, we started implementing a timer[1,2] based on the TTC of > the Zynq7000[0]. By now we have it up and running but with a high > deviation the longer it runs (already 30 seconds deviation after only 2 > minutes). > > This deviation originates from a few problems we have: > - The timers in TTC only provide a 16 Bit width -> high number of IRQs > when trying to achieve high precision > - The input clock is 133MHz and can only be prescaled by a division of > 2^(n+1) with 0 < n <= 16 -> hard to work with?
As far as I understood the manual correctly, there are three different reference clocks you can choose from. > > Currently we implement it similar to the imx6 timer, by generating IRQs > when a match in the MATCH0 register is acknowledged. > > I'm not very experienced in this topic and any help is appreciated on > how to resolve the deviation issues or how to implement it in a better > way - e.g. by using a different hardware timer which I didn't discover > in the TRM. > > Additionally I'd like to know if there is an easy way to configure the > maximum RAM of a platform in seL4/Genode apart from limiting it in > 'contrib/sel4-*/src/kernel/sel4/include/plat/*/plat/machine/hardware.h'? You hard-coded TICKS_PER_MS to "519", according to your comment in [1] Line 88 the prescale value N calculates to: count/2^(N+1) But you set the prescale value to "8". That means count/2^(8+1) = count/512. And 519 * 512 * 1000 ~= 266 MHz, isn't it? I strongly assume you are working with wrong assumptions regarding your clocking values. Regards Stefan > > Best regards, > Alex > > PS: As Zynq7000 platform we use the Digilent Zybo[3]. > > [0]: > https://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf > [1]: > https://github.com/irgendwie/genode/blob/rtcr-19.08-ttc/repos/base/src/timer/ttc/time_source.cc > [2]: > https://github.com/irgendwie/genode/blob/rtcr-19.08-ttc/repos/base/src/timer/ttc/time_source.h > [3]: > https://store.digilentinc.com/zybo-zynq-7000-arm-fpga-soc-trainer-board/ > [4]: > https://github.com/irgendwie/genode/commit/60ffef31b52d6566f481b3de87b4720f3251f6ec > > _______________________________________________ > Genode users mailing list > [email protected] > https://lists.genode.org/listinfo/users -- Stefan Kalkowski Genode labs https://github.com.skalk | https://genode.org _______________________________________________ Genode users mailing list [email protected] https://lists.genode.org/listinfo/users
