[PATCH] drm/stm: repair runtime power management

[Yannick FERTRE]

On 3/9/20 12:57 PM, Marek Vasut wrote:
> 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 ?
Hi Marek,
I tested the patch &  it generate an error when I try wake up / sleep 
the board STM32MP1 DK2 with weston application.
It need an additional patch 
drm-stm-ltdc-remove-call-of-pm-runtime-functions.

Thanks for the patch.

Tested-by: Yannick Fertre <yannick.fertre at st.com>


> 
>>   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
>>
> 
>