On 24.01.2018 10:51, Philippe CORNU wrote: > Hi Brian, > > On 01/23/2018 10:15 PM, Brian Norris wrote: >> Hi Philippe, >> >> On Thu, Jan 18, 2018 at 11:40:48AM +0000, Philippe CORNU wrote: >>> On 01/11/2018 12:16 PM, Philippe CORNU wrote: >>>> To be honest, I do not really like the memcpy here too and I agree with >>>> you regarding the BE issue. >>>> >>>> My first "stm" driver (ie. before using this "freescale/rockchip" >>>> dw-mipi-dsi driver with the memcpy) used the "exact" same code as the >>>> Tegra dsi tegra_dsi_writesl() function with the 2 loops. >>>> >>>> https://elixir.free-electrons.com/linux/v4.14/source/drivers/gpu/drm/tegra/dsi.c#L1248 >>>> >>>> >>>> IMHO, it is better than memcpy... >>>> I added these 3 "documentation" lines, maybe we may reuse them or >>>> something similar... >>>> >>>> /* >>>> * Write 8-bit payload data into the 32-bit payload data register. >>>> * ex: payload data "0x01, 0x02, 0x03, 0x04, 0x05, 0x06" will become >>>> * "0x04030201 0x00000605" 32-bit writes >>>> */ >>>> >>>> Not sure it helps to fix the BE issue but we may add a TODO stating that >>>> "this loop has not been tested on BE"... >>>> >>>> What is your opinion? >> I'm sorry, I don't think I noticed your reply here. I'm trying to unbury >> some email, but that's sometimes a losing battle... >> >> That code actually does look correct, and it's perhaps marginally >> better-looking in my opinion. It's up to you if you want to propose >> another patch :) At this point, it's only a matter of nice code, not >> correctness I believe. >> >>> As your patch has been merged, I have few short questions and for each >>> related new patch, I would like to know if you prefer that I implement >>> it or if you prefer to do it by yourself, it's really like you want, on >>> my side, no problem to make them all, some or none, I don't want us to >>> implement these in parallel :-) >>> >>> * Do you have any opinion regarding Tegra-like loops vs the memcpy? (see >>> my comment above) If you think the Tegra-like loops is a better approach >>> than memcpy, there is a small patch to write. >> My opinion is above. >> > I do not know yet if I will send a patch but several reasons may push me > to do it: > * Andrzej proposed a nicer code in his last review so it means the > actual code with memcpy's is "not so nice" (even if it works fine) I was not against memcpy, I have just suggested to abstract the code out to some helper function. Regarding memcpy vs loop I would prefer memcpy - simpler code, but it is looks less important that abstracting out. Regards Andrzej > * Several dsi drivers use the Tegra-like loops (Tegra, intel,... ) and > in vc4/exynos/mtk drivers memcpy is not used, msm uses memcpy... well, > not sure it is then a good argument, different solutions for different hw... > * Coming cadence dsi bridge driver uses Tegra-like loops. > * I think my read function will also have Tegra-like loops, if it is the > case, it could be nice to have something homogeneous... > > Anyway, it is not an important point : ) > >>> * Returned value with number of bytes received/transferred: there is a >>> small patch to write >> I don't think I followed that one very well. I'm not sure my opinion >> really matters, as long as you get someone else to agree. I do not plan >> to write any such patch in the near term. >> >>> * Regarding read operations: I propose to add a TODO + DRM_WARN in case >>> someone want to use the API for read operations. Note that I plan to >>> implement the read feature but I do not know yet when and maybe Rockchip >>> people already have something ~ready? >> The warning would be nice to do now, regardless. >> >> Rockchip folks wrote up something for read support here [1], but it's >> based on a semi-forked version of the driver (we're trying to clean up >> the divergence, but it's not there yet). Perhaps it would provide useful >> fodder for your work. I don't think Rockchip is immediately working on >> upstreaming this particular patch, so it's totally fair to handle it >> yourself. It's got the GPL sign-off ;) >> >> Brian >> >> [1] https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/863347 >> > Very good information, I will have a look, > many thanks > Philippe :-) _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
