Quoting Jagan Teki (2020-08-31 09:14:36)
> The current rockchip fractional approximation overflow the desired
> rate if parent rate is lower than the (rate * 20) for few clocks like
> dclk_vopb_frac.
>
> The overflow condition has observed in px30 for dclk_vopb_frac
> clock with an input rate of 71.1MHz and parent rate of 24MHz is,
>
> [ 2.543280] rockchip-drm display-subsystem: bound ff460000.vop (ops
> vop_component_ops)
Can you remove timestamps?
> [ 2.557313] rockchip-drm display-subsystem: bound ff470000.vop (ops
> vop_component_ops)
> [ 2.566356] rockchip-drm display-subsystem: bound ff140000.syscon:lvds
> (ops rockchip_lvds_component_ops)
> [ 2.576999] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [ 2.592177] Unexpected kernel BRK exception at EL1
> [ 2.597551] Internal error: ptrace BRK handler: f20003e8 [#1] PREEMPT SMP
> [ 2.605143] Modules linked in:
> [ 2.608566] CPU: 1 PID: 31 Comm: kworker/1:1 Tainted: G U
> 5.8.0-rc1-15632-g97edd822b844 #30
> [ 2.619363] Hardware name: Engicam PX30.Core C.TOUCH 2.0 10.1" Open Frame
> (DT)
> [ 2.627460] Workqueue: events deferred_probe_work_func
> [ 2.633209] pstate: 20000005 (nzCv daif -PAN -UAO BTYPE=--)
> [ 2.639445] pc : rational_best_approximation+0xc4/0xd0
> [ 2.645194] lr : rockchip_fractional_approximation+0xa8/0xe0
> [ 2.651520] sp : ffff800011ea31c0
> [ 2.655222] x29: ffff800011ea31c0 x28: ffff00007a4ecd50
> [ 2.661162] x27: ffff00007d042600 x26: 000000000439fca3
> [ 2.667102] x25: 0000000000000000 x24: ffff800011ac9948
> [ 2.673033] x23: ffff800011ea3308 x22: ffff00007d042418
> [ 2.678973] x21: ffff800011ea3240 x20: ffff800011ea3238
> [ 2.684904] x19: ea47000000000000 x18: 0000000000000000
> [ 2.690836] x17: 0000000000000500 x16: 0000000000000001
> [ 2.696775] x15: ffffffffffffffff x14: 0000000000000000
> [ 2.702707] x13: 0000000000000000 x12: 0000003c00000000
> [ 2.708647] x11: 0000000000000030 x10: 0101010101010101
> [ 2.714586] x9 : 0000032000000320 x8 : 7f7f7f7f7f7f7f7f
> [ 2.720517] x7 : 000000a3c59050d3 x6 : 0000000000000030
> [ 2.726457] x5 : ffff800011ea3240 x4 : ffff800011ea3238
> [ 2.732397] x3 : 000000000000ffff x2 : 000000000000ffff
> [ 2.738329] x1 : 00000000016e3600 x0 : 0000000001497e00
> [ 2.744269] Call trace:
> [ 2.747005] rational_best_approximation+0xc4/0xd0
> [ 2.752365] clk_fd_round_rate+0x8c/0x110
> [ 2.756846] clk_composite_round_rate+0x30/0x40
> [ 2.761917] clk_core_determine_round_nolock.part.30+0x44/0x80
> [ 2.768442] clk_core_round_rate_nolock+0x78/0x80
> [ 2.773701] clk_mux_determine_rate_flags+0xd8/0x200
> [ 2.779253] clk_mux_determine_rate+0x10/0x20
> [ 2.784124] clk_core_determine_round_nolock.part.30+0x1c/0x80
> [ 2.790639] clk_core_round_rate_nolock+0x78/0x80
> [ 2.795900] clk_core_round_rate_nolock+0x5c/0x80
> [ 2.801159] clk_round_rate+0x64/0xf0
> [ 2.805254] vop_crtc_mode_fixup+0x2c/0x60
> [ 2.809828] drm_atomic_helper_check_modeset+0x95c/0xae0
> [ 2.815767] drm_atomic_helper_check+0x1c/0xa0
> [ 2.820738] drm_atomic_check_only+0x43c/0x760
> [ 2.825705] drm_atomic_commit+0x18/0x60
> [ 2.830095] drm_client_modeset_commit_atomic.isra.16+0x17c/0x250
> [ 2.836911] drm_client_modeset_commit_locked+0x58/0x1a0
> [ 2.842851] drm_client_modeset_commit+0x2c/0x50
> [ 2.848014] drm_fb_helper_restore_fbdev_mode_unlocked+0x70/0xd0
> [ 2.854730] drm_fb_helper_set_par+0x2c/0x60
> [ 2.859497] fbcon_init+0x3c0/0x540
> [ 2.863400] visual_init+0xac/0x100
> [ 2.867298] do_bind_con_driver+0x1e4/0x3a0
> [ 2.871973] do_take_over_console+0x140/0x200
> [ 2.876843] do_fbcon_takeover+0x6c/0xe0
> [ 2.881228] fbcon_fb_registered+0x10c/0x120
> [ 2.886005] register_framebuffer+0x1f0/0x340
> [ 2.890878] __drm_fb_helper_initial_config_and_unlock+0x318/0x4a0
> [ 2.897790] drm_fb_helper_initial_config+0x3c/0x50
> [ 2.903244] rockchip_drm_fbdev_init+0x5c/0xf0
> [ 2.908202] rockchip_drm_bind+0x194/0x1e0
> [ 2.912785] try_to_bring_up_master+0x164/0x1d0
> [ 2.917851] component_master_add_with_match+0xac/0xf0
> [ 2.923597] rockchip_drm_platform_probe+0x238/0x2e0
> [ 2.929150] platform_drv_probe+0x50/0xa0
> [ 2.933631] really_probe+0xd4/0x330
> [ 2.937628] driver_probe_device+0x54/0xb0
> [ 2.942207] __device_attach_driver+0x80/0xc0
> [ 2.947078] bus_for_each_drv+0x78/0xd0
> [ 2.951365] __device_attach+0xd4/0x130
> [ 2.955652] device_initial_probe+0x10/0x20
> [ 2.960328] bus_probe_device+0x90/0xa0
> [ 2.964616] deferred_probe_work_func+0x6c/0xa0
> [ 2.969685] process_one_work+0x1e4/0x360
> [ 2.974166] worker_thread+0x208/0x480
> [ 2.978358] kthread+0x150/0x160
> [ 2.981968] ret_from_fork+0x10/0x18
Wow this stack is huge.
> [ 2.985970] Code: d65f03c0 d2800008 d2800027 17ffffe8 (d4207d00)
>
> This happened because the fractional divider does not apply if parent_rate
> is lower than (rate * 20).
>
> So, this patch is trying to fix that overflow clock and switch to half-div
> instead computing fractioanl approximation.
>
> Some part of the patch is referenced from below BSP commit:
>
> commit <88a5404a2277> ("clk: rockchip: fix up the
> rockchip_fractional_approximation")
>
> commit <4186a0e4239b> ("clk: rockchip: Add supprot to limit input rate
> for fractional divider")
Not sure what these are. Do we need random commit hashes in the log that
reference not-upstream patches? Seems like it could be left below the
triple dash and anyone can reference the mailing list if they really
care.
>
> Signed-off-by: Jagan Teki <ja...@amarulasolutions.com>
> Signed-off-by: Finley Xiao <finley.x...@rock-chips.com>
> ---
Any Fixes tag?
> drivers/clk/rockchip/clk-px30.c | 12 ++++++------
> drivers/clk/rockchip/clk.c | 9 +++++++++
> 2 files changed, 15 insertions(+), 6 deletions(-)
>
