| openpowerbot | [slack] <joel> @Jan Vrany Thanks for pointing out that glibc fix! I was the one that broke it with a patch to upstream buildroot, so I should have seen that coming 🤦♂️🏼 | 04:42 |
|---|---|---|
| openpowerbot | [slack] <joel> @Jan Vrany @Boris Shingarov I have some prebuilt images you can experiment with here: | 04:51 |
| openpowerbot | [slack] <joel> | 04:51 |
| openpowerbot | [slack] <joel> https://github.com/shenki/linux-on-microwatt | 04:51 |
| openpowerbot | [slack] <joel> | 04:51 |
| openpowerbot | [slack] <joel> Feel free to use the issue tracker to keep track of problems if you have any. | 04:51 |
| openpowerbot | [slack] <joel> Regarding your SIGILL, it looks like that's a FPU instruction that it's crashing on: | 07:39 |
| openpowerbot | [slack] <joel> ```$ disppc da0300c0 | 07:39 |
| openpowerbot | [slack] <joel> 0:da 03 00 c0 stfd f16,192(r3)``` | 07:39 |
| openpowerbot | [slack] <joel> Does your gateware have the FPU enabled? | 07:39 |
| openpowerbot | [slack] <Jan Vrany> @joel: OK, I'll open a PR against your repo with the glibc fix later today. | 08:33 |
| openpowerbot | [slack] <Jan Vrany> > Feel free to use the issue tracker | 08:33 |
| openpowerbot | [slack] <Jan Vrany> Sure, but your buildroot repo does not seem to have issues enabled. | 08:33 |
| openpowerbot | [slack] <Jan Vrany> | 08:33 |
| openpowerbot | [slack] <Jan Vrany> > Regarding your SIGILL, it looks like that's a FPU | 08:33 |
| openpowerbot | [slack] <Jan Vrany> Good point. I've got the gateware from @Boris Shingarov - I assume it has FPU since he run linux on it at some point. | 08:33 |
| openpowerbot | [slack] <Jan Vrany> But let me double check. | 08:33 |
| openpowerbot | [slack] <Jan Vrany> | 08:33 |
| openpowerbot | [slack] <Jan Vrany> Thanks! | 08:33 |
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| openpowerbot_ | [slack] <joel> I didn't mean the buildroot repo, I mean the linux-on-microwatt one I linked to | 08:49 |
| openpowerbot_ | [slack] <joel> I've updated the buildroot repo with a fix for the glibc issue | 08:49 |
| openpowerbot_ | [slack] <joel> @Jan Vrany Which FPGA are you using? | 08:49 |
| openpowerbot_ | [slack] <joel> The A7-35T or the 100T? | 08:49 |
| openpowerbot_ | [slack] <joel> The fusesoc config for the 35T defaults to no FPU. I use the 100T so I didn't realise; I should update the Linux instructions to include `--has_fpu` | 08:51 |
| openpowerbot_ | [slack] <Jan Vrany> A7-35T I believe. I'll double-check once I get to the office. | 09:10 |
| openpowerbot_ | [slack] <Jan Vrany> Yes, it is 35T. | 09:48 |
| openpowerbot_ | [slack] <Jan Vrany> I assume the gateware from https://github.com/shenki/linux-on-microwatt/tree/master/images is for 100T so it won't work on mine. | 10:04 |
| openpowerbot_ | [slack] <Jan Vrany> I do not have Vivado so cannot build gatrware myself, but I'll ask @Boris Shingarov to build one for me. | 10:04 |
| openpowerbot_ | [slack] <Jan Vrany> I'll get back once we try this - whether it works or not. | 10:04 |
| openpowerbot_ | [slack] <Jan Vrany> Thanks again! | 10:04 |
| openpowerbot_ | [slack] <Boris Shingarov> > The fusesoc config for the 35T defaults to no FPU. I use the 100T so I didn't realise | 10:43 |
| openpowerbot_ | [slack] <Boris Shingarov> Ok that explains everything!!! I didn't realise this and thought `fusesoc --target=arty_a7-100 microwatt` and `fusesoc --target=arty_a7-35 microwatt` would produce literally the same circuit just mapped to different devices. | 10:43 |
| openpowerbot_ | [slack] <Boris Shingarov> @Jan Vrany I am rebuilding with FPU now! | 10:43 |
| openpowerbot_ | [slack] <joel> Now I recall why it's disabled by default, the FPU doesn't fit on that one | 10:44 |
| openpowerbot_ | [slack] <Boris Shingarov> Oh so one can't run microwatt-linux on 35T? | 10:44 |
| openpowerbot_ | [slack] <joel> If you poke around in microwatt.core you can see the different configurations. The larger FPGAs default to using more resources, etc. | 10:45 |
| openpowerbot_ | [slack] <joel> I'm not sure. @Paul Mackerras Is there anything we can trim out to get the FPU to fit on the 35T? | 10:45 |
| openpowerbot_ | [slack] <Paul Mackerras> I have been trying to convert it to microprogrammed control with the idea of reducing the amount of logic, but I haven't completed that yet. It's a big job actually. | 10:47 |
| openpowerbot_ | [slack] <Jan Vrany> OK, so IIUC the conclusion is that for now, there's no "easy" way to run linux on 35T - one needs 100T. That's good to know! : - ) Thanks! | 10:54 |
| openpowerbot_ | [slack] <joel> Sorry to mislead. I should update the instructions to make that clear | 10:54 |
| openpowerbot_ | [slack] <Jan Vrany> No problem at all! | 10:56 |
| openpowerbot_ | [slack] <Paul Mackerras> You can enable the software FP emulation in the kernel, but it doesn't handle all the ISA v3.0b FP instructions unfortunately | 10:57 |
| openpowerbot_ | [slack] <Jan Vrany> Good point, I can try that and see how far I go with it. Thanks! | 11:02 |
| openpowerbot_ | [slack] <Paul Mackerras> From memory at least fctid is not implemented. You could have a look at extending the soft fp emulation; I started looking at that ages ago but it was more fun to design an FPU 🙂 | 11:03 |
| openpowerbot_ | [slack] <Boris Shingarov> On an unrelated subject: | 16:32 |
| openpowerbot_ | [slack] <Boris Shingarov> What maps the DRAM at 0x40000000 to 0x00000000? | 16:32 |
| openpowerbot_ | [slack] <Boris Shingarov> I am trying to place u-boot in BRAM (for a board where SPI flash is not [yet] accessible) and the constant 0x0c000000 is coded in a whole bunch of config places, which I find to be reasonable to assume that the main DRAM is mapped to 0x0. `microwatt/include/microwatt_soc.h` represents this as | 16:32 |
| openpowerbot_ | [slack] <Boris Shingarov> ```#define MEMORY_BASE 0x00000000 /* "Main" memory alias, either BRAM or DRAM */ | 16:32 |
| openpowerbot_ | [slack] <Boris Shingarov> #define DRAM_BASE 0x40000000 /* DRAM if present */ | 16:32 |
| openpowerbot_ | [slack] <Boris Shingarov> #define BRAM_BASE 0x80000000 /* Internal BRAM */``` | 16:32 |
| openpowerbot_ | [slack] <Boris Shingarov> but where in the gateware source is this alias? It looks like when I have **both** DRAM and BRAM, both do work fine when I address them at the high addresses, but DRAM is not mapped to 0. Perhaps this is a simple switch? | 16:32 |
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