mainlining shenanigans
1bf6ad622b
If we restrict this helper to only kms drivers (which is the case) we can look up the correct mode easily ourselves. But it's a bit tricky: - All legacy drivers look at crtc->hwmode. But that is updated already at the beginning of the modeset helper, which means when we disable a pipe. Hence the final timestamps might be a bit off. But since this is an existing bug I'm not going to change it, but just try to be bug-for-bug compatible with the current code. This only applies to radeon&amdgpu. - i915 tries to get it perfect by updating crtc->hwmode when the pipe is off (i.e. vblank->enabled = false). - All other atomic drivers look at crtc->state->adjusted_mode. Those that look at state->requested_mode simply don't adjust their mode, so it's the same. That has two problems: Accessing crtc->state from interrupt handling code is unsafe, and it's updated before we shut down the pipe. For nonblocking modesets it's even worse. For atomic drivers try to implement what i915 does. To do that we add a new hwmode field to the vblank structure, and update it from drm_calc_timestamping_constants(). For atomic drivers that's called from the right spot by the helper library already, so all fine. But for safety let's enforce that. For legacy driver this function is only called at the end (oh the fun), which is broken, so again let's not bother and just stay bug-for-bug compatible. The benefit is that we can use drm_calc_vbltimestamp_from_scanoutpos directly to implement ->get_vblank_timestamp in every driver, deleting a lot of code. v2: Completely new approach, trying to mimick the i915 solution. v3: Fixup kerneldoc. v4: Drop the WARN_ON to check that the vblank is off, atomic helpers currently unconditionally call this. Recomputing the same stuff should be harmless. v5: Fix typos and move misplaced hunks to the right patches (Neil). v6: Undo hunk movement (kbuild). Cc: Mario Kleiner <mario.kleiner@tuebingen.mpg.de> Cc: Eric Anholt <eric@anholt.net> Cc: Rob Clark <robdclark@gmail.com> Cc: linux-arm-msm@vger.kernel.org Cc: freedreno@lists.freedesktop.org Cc: Alex Deucher <alexander.deucher@amd.com> Cc: Christian König <christian.koenig@amd.com> Cc: Ben Skeggs <bskeggs@redhat.com> Reviewed-by: Neil Armstrong <narmstrong@baylibre.com> Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com> Link: http://patchwork.freedesktop.org/patch/msgid/20170509140329.24114-4-daniel.vetter@ffwll.ch |
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Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.