On 21/02/2020 10:27, CK Hu wrote: > Hi, Enric: > > On Fri, 2020-02-21 at 09:56 +0100, Enric Balletbo i Serra wrote: >> Hi CK, >> >> Thanks for your quick answer. >> >> On 21/2/20 5:39, CK Hu wrote: >>> Hi, Enric: >>> >>> On Thu, 2020-02-20 at 18:21 +0100, Enric Balletbo i Serra wrote: >>>> Dear all, >>>> >>>> Those patches are intended to solve an old standing issue on some >>>> Mediatek devices (mt8173, mt2701 and mt2712) in a slightly different way >>>> to the precedent series. >>>> >>>> Up to now both drivers, clock and drm are probed with the same device tree >>>> compatible. But only the first driver get probed, which in effect breaks >>>> graphics on those devices. >>>> >>>> The version eight of the series tries to solve the problem with a >>>> different approach than the previous series but similar to how is solved >>>> on other Mediatek devices. >>>> >>>> The MMSYS (Multimedia subsystem) in Mediatek SoCs has some registers to >>>> control clock gates (which is used in the clk driver) and some registers >>>> to set the routing and enable the differnet blocks of the display >>>> and MDP (Media Data Path) subsystem. On this series the clk driver is >>>> not a pure clock controller but a system controller that can provide >>>> access to the shared registers between the different drivers that need >>>> it (mediatek-drm and mediatek-mdp). And the biggest change is, that in >>>> this version, clk driver is the entry point (parent) which will trigger >>>> the probe of the corresponding mediatek-drm driver and pass its MMSYS >>>> platform data for display configuration. >>> >>> When mmsys is a system controller, I prefer to place mmsys in >>> drivers/soc/mediatek, and it share registers for clock, display, and mdp >>> driver. This means the probe function is placed in >>> drivers/soc/mediatek ,its display clock function, mdp clock function are >>> placed in drivers/clk, display routing are placed in drivers/gpu/drm, >>> and mdp routing are placed in dirvers/video. >>> >> >> I understand what you mean but I am not sure this makes the code clearer and >> useful. The driver in drivers/soc/mediatek will be a simple dummy implementation >> of a "simple-mfd" device (a driver that simply matches with >> "mediatek,mt8173-mmsys" and instantiates the "clk-mt8173-mm" and the >> "mediatek-drm" driver (note that mediatek-mdp" is already instantiated via >> device-tree). >> > > It's clear that mmsys is neither a pure clock controller nor a pure > routing controller for display and mdp. > >> It'd be nice had a proper device-tree with a "simple-mfd" for mmsys from the >> beginning representing how really hardwware is, but I think that, change this >> now, will break backward compatibility. > > Maybe this is a solution. Current device tree would work only on old > kernel version with a bug, so this mean there is no any device tree > works on kernel version without bug. Why do we compatible with such > device tree? > The idea behind this is, that the device-tree could be passed by some boot firmware, so that the OS do not care about it. For this we need a stable DTS as otherwise newer kernel with older FW would break. DTS is supposed to be just a different description of the HW like ACPI. So it has to be compatible (newer kernel with older DTS and if possible vice versa). Regards, Matthias > Regards, > CK > >> >> IMHO I think that considering the clk driver as entry point is fine, but this is >> something that the clock maintainers should decide. >> >> Also note that this is not only a MT8173 problem I am seeing the same problem on >> all other Mediatek SoCs. >> >> Thanks. >> >>> Regards, >>> CK >>> >>>> >>>> All this series was tested on the Acer R13 Chromebook only. >>>> >>>> For reference, here are the links to the old discussions: >>>> >>>> * v7: https://patchwork.kernel.org/project/linux-mediatek/list/?series=241217 >>>> * v6: https://patchwork.kernel.org/project/linux-mediatek/list/?series=213219 >>>> * v5: https://patchwork.kernel.org/project/linux-mediatek/list/?series=44063 >>>> * v4: >>>> * https://patchwork.kernel.org/patch/10530871/ >>>> * https://patchwork.kernel.org/patch/10530883/ >>>> * https://patchwork.kernel.org/patch/10530885/ >>>> * https://patchwork.kernel.org/patch/10530911/ >>>> * https://patchwork.kernel.org/patch/10530913/ >>>> * v3: >>>> * https://patchwork.kernel.org/patch/10367857/ >>>> * https://patchwork.kernel.org/patch/10367861/ >>>> * https://patchwork.kernel.org/patch/10367877/ >>>> * https://patchwork.kernel.org/patch/10367875/ >>>> * https://patchwork.kernel.org/patch/10367885/ >>>> * https://patchwork.kernel.org/patch/10367883/ >>>> * https://patchwork.kernel.org/patch/10367889/ >>>> * https://patchwork.kernel.org/patch/10367907/ >>>> * https://patchwork.kernel.org/patch/10367909/ >>>> * https://patchwork.kernel.org/patch/10367905/ >>>> * v2: No relevant discussion, see v3 >>>> * v1: >>>> * https://patchwork.kernel.org/patch/10016497/ >>>> * https://patchwork.kernel.org/patch/10016499/ >>>> * https://patchwork.kernel.org/patch/10016505/ >>>> * https://patchwork.kernel.org/patch/10016507/ >>>> >>>> Best regards, >>>> Enric >>>> >>>> Changes in v8: >>>> - Be a builtin_platform_driver like other mediatek mmsys drivers. >>>> - New patches introduced in this series. >>>> >>>> Changes in v7: >>>> - Add R-by from CK >>>> - Add R-by from CK >>>> - Fix check of return value of of_clk_get >>>> - Fix identation >>>> - Free clk_data->clks as well >>>> - Get rid of private data structure >>>> >>>> Enric Balletbo i Serra (2): >>>> drm/mediatek: Move MMSYS configuration to include/linux/platform_data >>>> clk/drm: mediatek: Fix mediatek-drm device probing >>>> >>>> Matthias Brugger (4): >>>> drm/mediatek: Use regmap for register access >>>> drm/mediatek: Omit warning on probe defers >>>> media: mtk-mdp: Check return value of of_clk_get >>>> clk: mediatek: mt8173: Switch MMSYS to platform driver >>>> >>>> drivers/clk/mediatek/Kconfig | 6 + >>>> drivers/clk/mediatek/Makefile | 1 + >>>> drivers/clk/mediatek/clk-mt2701-mm.c | 30 +++ >>>> drivers/clk/mediatek/clk-mt2712-mm.c | 44 +++++ >>>> drivers/clk/mediatek/clk-mt8173-mm.c | 172 ++++++++++++++++++ >>>> drivers/clk/mediatek/clk-mt8173.c | 104 ----------- >>>> drivers/gpu/drm/mediatek/mtk_disp_color.c | 5 +- >>>> drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 5 +- >>>> drivers/gpu/drm/mediatek/mtk_disp_rdma.c | 5 +- >>>> drivers/gpu/drm/mediatek/mtk_dpi.c | 12 +- >>>> drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 4 +- >>>> drivers/gpu/drm/mediatek/mtk_drm_ddp.c | 53 +++--- >>>> drivers/gpu/drm/mediatek/mtk_drm_ddp.h | 4 +- >>>> drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h | 56 +----- >>>> drivers/gpu/drm/mediatek/mtk_drm_drv.c | 113 +----------- >>>> drivers/gpu/drm/mediatek/mtk_drm_drv.h | 13 +- >>>> drivers/gpu/drm/mediatek/mtk_dsi.c | 8 +- >>>> drivers/gpu/drm/mediatek/mtk_hdmi.c | 4 +- >>>> drivers/media/platform/mtk-mdp/mtk_mdp_comp.c | 6 + >>>> include/linux/platform_data/mtk_mmsys.h | 73 ++++++++ >>>> 20 files changed, 401 insertions(+), 317 deletions(-) >>>> create mode 100644 drivers/clk/mediatek/clk-mt8173-mm.c >>>> create mode 100644 include/linux/platform_data/mtk_mmsys.h >>>> >>> >> >> _______________________________________________ >> Linux-mediatek mailing list >> Linux-mediatek@xxxxxxxxxxxxxxxxxxx >> http://lists.infradead.org/mailman/listinfo/linux-mediatek >
