[PATCH] drm/stm: repair runtime power management

[Marek Vasut]

On 3/9/20 11:35 AM, Yannick FERTRE wrote:
> Hello Marek,

Hi,

(please stop top-posting)

> Thank for your patch. Pm_runtime_put_sync is also done into function ltdc_crtc_mode_fixup.
> To avoid several call of Pm_runtime_put_sync, it could be better to check pm_runtime activity:
> 
> +	int ret;
>  
>  	DRM_DEBUG_DRIVER("\n");
>  
> +	if (!pm_runtime_active(ddev->dev)) {
> +		ret = pm_runtime_get_sync(ddev->dev);
> +		if (ret) {
> +			DRM_ERROR("Failed to enable crtc, cannot get sync\n");
> +			return;
> +		}
> +	}
> +

Where should this go ? And wouldn't that only hide nastier PM imbalance
issues ?

>  Best regards
> 
> Yannick Fertré
> 
> 
> -----Original Message-----
> From: Marek Vasut <marex at denx.de> 
> Sent: samedi 29 février 2020 23:17
> To: dri-devel at lists.freedesktop.org
> Cc: Marek Vasut <marex at denx.de>; Yannick FERTRE <yannick.fertre at st.com>; Philippe CORNU <philippe.cornu at st.com>; Benjamin Gaignard <benjamin.gaignard at linaro.org>; Vincent ABRIOU <vincent.abriou at st.com>; Maxime Coquelin <mcoquelin.stm32 at gmail.com>; Alexandre TORGUE <alexandre.torgue at st.com>; linux-stm32 at st-md-mailman.stormreply.com; linux-arm-kernel at lists.infradead.org
> Subject: [PATCH] drm/stm: repair runtime power management
> 
> 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);
>  
> --
> 2.25.0
> 


-- 
Best regards,
Marek Vasut