[PATCH] drm/stm: repair runtime power management

[Philippe CORNU]

On 2/29/20 11:16 PM, Marek Vasut wrote:
> Add missing pm_runtime_get_sync() into ltdc_crtc_atomic_enable() to
> match pm_runtime_put_sync() in ltdc_crtc_atomic_disable(), otherwise
> the LTDC might suspend via runtime PM, disable clock, and then fail
> to resume later on.
> 
> The test which triggers it is roughly -- run qt5 application which
> uses eglfs platform and etnaviv, stop the application, sleep for 15
> minutes, run the application again. This leads to a timeout waiting
> for vsync, because the LTDC has suspended, but did not resume.
> 
> Fixes: 35ab6cfbf211 ("drm/stm: support runtime power management")
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Yannick Fertré <yannick.fertre at st.com>
> Cc: Philippe Cornu <philippe.cornu at st.com>
> Cc: Benjamin Gaignard <benjamin.gaignard at linaro.org>
> Cc: Vincent Abriou <vincent.abriou at st.com>
> Cc: Maxime Coquelin <mcoquelin.stm32 at gmail.com>
> Cc: Alexandre Torgue <alexandre.torgue at st.com>
> To: dri-devel at lists.freedesktop.org
> Cc: linux-stm32 at st-md-mailman.stormreply.com
> Cc: linux-arm-kernel at lists.infradead.org
> ---
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 297 at drivers/gpu/drm/drm_atomic_helper.c:1494 drm_atomic_helper_wait_for_vblanks+0x1dc/0x200
> [CRTC:35:crtc-0] vblank wait timed out
> Modules linked in:
> CPU: 0 PID: 297 Comm: QSGRenderThread Not tainted 5.6.0-rc3-next-20200228-00010-g318bf0fc08ef #2
> Hardware name: STM32 (Device Tree Support)
> [<c010f18c>] (unwind_backtrace) from [<c010afb8>] (show_stack+0x10/0x14)
> [<c010afb8>] (show_stack) from [<c07b1d3c>] (dump_stack+0xb4/0xd0)
> [<c07b1d3c>] (dump_stack) from [<c011d8b8>] (__warn+0xd4/0xf0)
> [<c011d8b8>] (__warn) from [<c011dc4c>] (warn_slowpath_fmt+0x78/0xa8)
> [<c011dc4c>] (warn_slowpath_fmt) from [<c04a266c>] (drm_atomic_helper_wait_for_vblanks+0x1dc/0x200)
> [<c04a266c>] (drm_atomic_helper_wait_for_vblanks) from [<c04a510c>] (drm_atomic_helper_commit_tail+0
> x50/0x60)
> [<c04a510c>] (drm_atomic_helper_commit_tail) from [<c04a52a8>] (commit_tail+0x12c/0x13c)
> [<c04a52a8>] (commit_tail) from [<c04a53b4>] (drm_atomic_helper_commit+0xf4/0x100)
> [<c04a53b4>] (drm_atomic_helper_commit) from [<c04a2d38>] (drm_atomic_helper_set_config+0x58/0x6c)
> [<c04a2d38>] (drm_atomic_helper_set_config) from [<c04b1994>] (drm_mode_setcrtc+0x450/0x550)
> [<c04b1994>] (drm_mode_setcrtc) from [<c04ad570>] (drm_ioctl_kernel+0x90/0xe8)
> [<c04ad570>] (drm_ioctl_kernel) from [<c04ad8ac>] (drm_ioctl+0x2e4/0x32c)
> [<c04ad8ac>] (drm_ioctl) from [<c0246784>] (vfs_ioctl+0x20/0x38)
> [<c0246784>] (vfs_ioctl) from [<c02470f0>] (ksys_ioctl+0xbc/0x7b0)
> [<c02470f0>] (ksys_ioctl) from [<c0101000>] (ret_fast_syscall+0x0/0x54)
> Exception stack(0xee8f3fa8 to 0xee8f3ff0)
> 3fa0:                   00000005 adcbeb18 00000005 c06864a2 adcbeb18 00000001
> 3fc0: 00000005 adcbeb18 c06864a2 00000036 00000029 00000023 00000023 00000007
> 3fe0: b113b098 adcbeafc b1125413 b6155cf8
> ---[ end trace 2ad5ba954ceb767a ]---
> ---
>   drivers/gpu/drm/stm/ltdc.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 99bf93e8b36f..301de0498078 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -425,9 +425,12 @@ static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
>   				    struct drm_crtc_state *old_state)
>   {
>   	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
> +	struct drm_device *ddev = crtc->dev;
>   
>   	DRM_DEBUG_DRIVER("\n");
>   
> +	pm_runtime_get_sync(ddev->dev);
> +
>   	/* Sets the background color value */
>   	reg_write(ldev->regs, LTDC_BCCR, BCCR_BCBLACK);
>   
> 
Hi Marek,
Many thanks for your patch,
Acked-by: Philippe Cornu <philippe.cornu at st.com>
Tested-by: Yannick Fertre <yannick.fertre at st.com>


Hi Benjamin,
Could you please apply "drm/stm: ltdc: remove call of pm-runtime 
functions" **before** this one. Thank you.

Philippe :-)