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[Why] ramp_up_dispclk_with_dpp is to change dispclk, dppclk and dprefclk according to bandwidth requirement. call stack: rv1_update_clocks --> update_clocks --> dcn10_prepare_bandwidth / dcn10_optimize_bandwidth --> prepare_bandwidth / optimize_bandwidth. before change dcn hw, prepare_bandwidth will be called first to allow enough clock, watermark for change, after end of dcn hw change, optimize_bandwidth is executed to lower clock to save power for new dcn hw settings. below is sequence of commit_planes_for_stream: step 1: prepare_bandwidth - raise clock to have enough bandwidth step 2: lock_doublebuffer_enable step 3: pipe_control_lock(true) - make dchubp register change will not take effect right way step 4: apply_ctx_for_surface - program dchubp step 5: pipe_control_lock(false) - dchubp register change take effect step 6: optimize_bandwidth --> dc_post_update_surfaces_to_stream for full_date, optimize clock to save power at end of step 1, dcn clocks (dprefclk, dispclk, dppclk) may be changed for new dchubp configuration. but real dcn hub dchubps are still running with old configuration until end of step 5. this need clocks settings at step 1 should not less than that before step 1. this is checked by two conditions: 1. if (should_set_clock(safe_to_lower , new_clocks->dispclk_khz, clk_mgr_base->clks.dispclk_khz) || new_clocks->dispclk_khz == clk_mgr_base->clks.dispclk_khz) 2. request_dpp_div = new_clocks->dispclk_khz > new_clocks->dppclk_khz the second condition is based on new dchubp configuration. dppclk for new dchubp may be different from dppclk before step 1. for example, before step 1, dchubps are as below: pipe 0: recout=(0,40,1920,980) viewport=(0,0,1920,979) pipe 1: recout=(0,0,1920,1080) viewport=(0,0,1920,1080) for dppclk for pipe0 need dppclk = dispclk new dchubp pipe split configuration: pipe 0: recout=(0,0,960,1080) viewport=(0,0,960,1080) pipe 1: recout=(960,0,960,1080) viewport=(960,0,960,1080) dppclk only needs dppclk = dispclk /2. dispclk, dppclk are not lock by otg master lock. they take effect after step 1. during this transition, dispclk are the same, but dppclk is changed to half of previous clock for old dchubp configuration between step 1 and step 6. This may cause p-state warning intermittently. [How] for new_clocks->dispclk_khz == clk_mgr_base->clks.dispclk_khz, we need make sure dppclk are not changed to less between step 1 and 6. for new_clocks->dispclk_khz > clk_mgr_base->clks.dispclk_khz, new display clock is raised, but we do not know ratio of new_clocks->dispclk_khz and clk_mgr_base->clks.dispclk_khz, new_clocks->dispclk_khz /2 does not guarantee equal or higher than old dppclk. we could ignore power saving different between dppclk = displck and dppclk = dispclk / 2 between step 1 and step 6. as long as safe_to_lower = false, set dpclk = dispclk to simplify condition check. CC: Stable <stable@vger.kernel.org> Signed-off-by: Hersen Wu <hersenxs.wu@amd.com> Reviewed-by: Aric Cyr <Aric.Cyr@amd.com> Acked-by: Eryk Brol <eryk.brol@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.