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Message-ID: <d5546b48ea829316a8dbd2ecc27bbf05e70e8188.camel@ndufresne.ca>
Subject: Re: [RESEND PATCH v0 3/5] wave5 : Support runtime suspend/resume.
From: Nicolas Dufresne <nicolas@ndufresne.ca>
To: "jackson.lee" <jackson.lee@chipsnmedia.com>, "mchehab@kernel.org"
	 <mchehab@kernel.org>, "linux-media@vger.kernel.org"
	 <linux-media@vger.kernel.org>, "linux-kernel@vger.kernel.org"
	 <linux-kernel@vger.kernel.org>, Nas Chung <nas.chung@chipsnmedia.com>
Cc: "lafley.kim" <lafley.kim@chipsnmedia.com>, "b-brnich@ti.com"
	 <b-brnich@ti.com>
Date: Tue, 20 Feb 2024 14:06:34 -0500
In-Reply-To: <SE1P216MB1303CEEF6DFAB5FA7C69D645ED502@SE1P216MB1303.KORP216.PROD.OUTLOOK.COM>
References: <20240131013046.15687-1-jackson.lee@chipsnmedia.com>
	 <20240131013046.15687-4-jackson.lee@chipsnmedia.com>
	 <efe24b949a60034bf618eb3b8a8ba82e8a5dc99c.camel@ndufresne.ca>
	 <SE1P216MB130326E2C4BA7E723A8955C9ED512@SE1P216MB1303.KORP216.PROD.OUTLOOK.COM>
	 <20489b01f1ac9ab3e434ea4c17b4e0ccd84afa36.camel@ndufresne.ca>
	 <SE1P216MB1303CEEF6DFAB5FA7C69D645ED502@SE1P216MB1303.KORP216.PROD.OUTLOOK.COM>
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Le mardi 20 f=C3=A9vrier 2024 =C3=A0 05:12 +0000, jackson.lee a =C3=A9crit=
=C2=A0:
> Hello Nicolas
>=20
> Thanks your comment.
>=20
>=20
> A pause is common state for media player, but our VPU could trigger an in=
terrupt regardless of a player state.
> So at a pause state if a power turns off, our driver becomes hang-up.
> I think power on/off should be controlled in the open/close function.

Please, avoid top posting, this breaks the discussion completely. Walk thro=
ugh
the comments, and reply to them underneath so we can have a proper discussi=
on.

In our experience, and with the rework of the driver we did during up-strea=
ming,
there is no more un-solicited IRQ. The way the driver state machine has bee=
n
built, when the m2m framework is idle (no jobs are active or pending), it m=
eans
the firmware is stalled, waiting on some application action. Combined with =
a
timer of course, so we don't actively suspend/resume, this seems adequate p=
lace
to do power management. If that application action never occurred passed a
decent delay, we can suspend. Later on, user actions like qbuf, will lead t=
o
device_run() to be called again, and it would be a good place to resume it.
There is of course other places where you'll have to make sure the hardware=
 is
resumed, like on close, as you want to remove the instance. There is also s=
mall
queries here and there that need to be surrounded with resume/put, but with=
 the
redesign, most of the HW access now take place inside device_run() only.

Open/Close is not invalid, but it has a lot of issues, as any random applic=
ation
can endup disabling the kernel ability to save power. Personally, I think w=
e
should at least give it a try, and document valid reason not to do so if we=
 find
hardware issues. Otherwise, this sounds like all we care is ticking the box
"this driver has runtime PM" without actually caring about effective power
saving.

Nicolas

>=20
> Thanks.
>=20
> > Le lundi 19 f=C3=A9vrier 2024 =C3=A0 04:04 +0000, jackson.lee a =C3=A9c=
rit=C2=A0:
> > > Hi Nicolas
> > >=20
> > >=20
> > > > This seems very unnatural. We do the get() in "start_streaming()",
> > > > but the
> > > > put() is only done when the device is closed, or when the driver is
> > > > removed. As this is not balanced, you seem to have to check the
> > > > suspended condition all over the place.
> > > >=20
> > > > I think we could aim for start_streaming()/stop_streaming() for you=
r
> > > > get/put placement. At least they will be bound to an entirely balan=
ced
> > API.
> > > > But then, a media player in paused sate will prevent that device
> > > > from being suspended.
> > > >=20
> > > > If the HW is capable of preserving enough state, and From the short
> > > > doc I have it gives me the impression it can preserve that, I'd
> > > > suggest to follow what hantro driver is doing. What is does is that
> > > > it will do get() in device_run(), and put() whenever the job
> > > > completes. This driver has been designed so when there is no job, i=
t
> > > > means the firmware is currently idle and looking for more work. So
> > > > it seems like the perfect moment to do suspend it.
> > > >=20
> > >=20
> > > Thanks your comment,
> > >=20
> > > Currently they are not balanced,
> > > If we puts "the put functon" into the stop_streaming, our hw is stall=
ed
> > until doing wake-up command, so our v4l2 device become block.
> > > so I'd like to update the below instead of calling get at the
> > start_streaming function.
> > >=20
> > >=20
> > > @@ -1867,6 +1868,13 @@ static int wave5_vpu_open_dec(struct file
> > > *filp)
> > >=20
> > >         wave5_vdi_allocate_sram(inst->dev);
> > >=20
> > > +       err =3D pm_runtime_resume_and_get(inst->dev->dev);
> > > +       if (err) {
> > > +               dev_err(inst->dev->dev, "decoder runtime resume
> > failed %d\n", err);
> > > +               ret =3D -EINVAL;
> > > +               goto cleanup_inst;
> > > +       }
> > > +
> > >         return 0;
> >=20
> > I guess we need to discuss the power management strategy for this devic=
e.
> > If you do resume_and_get() in open(), and then put in close(), that see=
ms
> > balanced. But in term of power saving, it might not be very strong. If =
you
> > have a media player that is set to pause and then placed in the backgro=
und,
> > you still keep the IP running. This is extremely common, since applicat=
ion
> > cannot close their device without loosing the reference frames, and thu=
s
> > having to do extra work on resume to seek back to the previous sync poi=
nt
> > and drop unneeded frames.
> >=20
> > It seems like the whole point of asking the firmware to save the state =
and
> > suspend is to be able to do so while there is meaningful sate in the fi=
rt
> > place.
> > If we are to suspend only when there is no meaningful state, we could j=
ust
> > free all resources and power it off completely. (This is just for
> > illustration, its probably to slow to boot the firmware at runtime)
> >=20
> >=20
> > I understand you suffered lockup with a start_streaming() for
> > resume_and_get(), and stop_streaming() for put(), this may simply indic=
ate
> > that some hardware access are needed between these two. Can you write d=
own
> > a power management plan that would effectively save power in common use
> > cases ? We can certainly help in refactoring the code to make that happ=
en.
> >=20
> > Nicolas
> >=20
> > >=20
> > > > Le mercredi 31 janvier 2024 =C3=A0 10:30 +0900, jackson.lee a =C3=
=A9crit=C2=A0:
> > > > > There are two device run-time PM callbacks defined in 'struct
> > > > dev_pm_ops'
> > > > > int (*runtime_suspend)(struct device *dev); int
> > > > > (*runtime_resume)(struct device *dev);
> > > >=20
> > > > I wonder how useful is it to teach everyone what the generic 'struc=
t
> > > > dev_pm_ops'
> > > > contains. Perhaps you simply wanted that this patch implement both
> > > > suspend and resume ops ?
> > > >=20
> > > > >=20
> > > > > Signed-off-by: Jackson Lee <jackson.lee@chipsnmedia.com>
> > > > > Signed-off-by: Nas Chung <nas.chung@chipsnmedia.com>
> > > > > ---
> > > > >  .../platform/chips-media/wave5/wave5-hw.c     |  5 +-
> > > > >  .../chips-media/wave5/wave5-vpu-dec.c         |  9 +++
> > > > >  .../chips-media/wave5/wave5-vpu-enc.c         |  9 +++
> > > > >  .../platform/chips-media/wave5/wave5-vpu.c    | 68
> > +++++++++++++++++++
> > > > >  .../platform/chips-media/wave5/wave5-vpuapi.c |  7 ++
> > > > > .../media/platform/chips-media/wave5/wave5.h  |  3 +
> > > > >  6 files changed, 99 insertions(+), 2 deletions(-)
> > > > >=20
> > > > > diff --git a/drivers/media/platform/chips-media/wave5/wave5-hw.c
> > > > > b/drivers/media/platform/chips-media/wave5/wave5-hw.c
> > > > > index 8ad7f3a28ae1..8aade5a38439 100644
> > > > > --- a/drivers/media/platform/chips-media/wave5/wave5-hw.c
> > > > > +++ b/drivers/media/platform/chips-media/wave5/wave5-hw.c
> > > > > @@ -503,6 +503,7 @@ int wave5_vpu_build_up_dec_param(struct
> > > > > vpu_instance
> > > > *inst,
> > > > >  	/* This register must be reset explicitly */
> > > > >  	vpu_write_reg(inst->dev, W5_CMD_EXT_ADDR, 0);
> > > > >  	vpu_write_reg(inst->dev, W5_CMD_NUM_CQ_DEPTH_M1,
> > > > > (COMMAND_QUEUE_DEPTH - 1));
> > > > > +	vpu_write_reg(inst->dev, W5_CMD_ERR_CONCEAL, 0);
> > > >=20
> > > > In some way, the relation between suspend and this register write i=
s
> > > > not obvious. If its not related, please do this in its own patch.
> > > > Otherwise you want to explain why you needed this (possibly just in
> > > > the commit message).
> > > >=20
> > > > >=20
> > > > >  	ret =3D send_firmware_command(inst, W5_CREATE_INSTANCE, true,
> > > > > NULL,
> > > > NULL);
> > > > >  	if (ret) {
> > > > > @@ -1075,8 +1076,8 @@ int wave5_vpu_re_init(struct device *dev, u=
8
> > > > > *fw,
> > > > size_t size)
> > > > >  	return setup_wave5_properties(dev);  }
> > > > >=20
> > > > > -static int wave5_vpu_sleep_wake(struct device *dev, bool
> > > > > i_sleep_wake,
> > > > const uint16_t *code,
> > > > > -				size_t size)
> > > > > +int wave5_vpu_sleep_wake(struct device *dev, bool i_sleep_wake,
> > > > > +const
> > > > uint16_t *code,
> > > > > +			 size_t size)
> > > > >  {
> > > > >  	u32 reg_val;
> > > > >  	struct vpu_buf *common_vb;
> > > > > diff --git
> > > > > a/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
> > > > > b/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
> > > > > index ef227af72348..328a7a8f26c5 100644
> > > > > --- a/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
> > > > > +++ b/drivers/media/platform/chips-media/wave5/wave5-vpu-dec.c
> > > > > @@ -5,6 +5,7 @@
> > > > >   * Copyright (C) 2021-2023 CHIPS&MEDIA INC
> > > > >   */
> > > > >=20
> > > > > +#include <linux/pm_runtime.h>
> > > > >  #include "wave5-helper.h"
> > > > >=20
> > > > >  #define VPU_DEC_DEV_NAME "C&M Wave5 VPU decoder"
> > > > > @@ -1387,9 +1388,17 @@ static int
> > > > > wave5_vpu_dec_start_streaming(struct
> > > > > vb2_queue *q, unsigned int count
> > > > >=20
> > > > >  	if (q->type =3D=3D V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE && inst-
> > > state
> > > > > =3D=3D
> > > > VPU_INST_STATE_NONE) {
> > > > >  		struct dec_open_param open_param;
> > > > > +		int err =3D 0;
> > > > >=20
> > > > >  		memset(&open_param, 0, sizeof(struct dec_open_param));
> > > > >=20
> > > > > +		err =3D pm_runtime_resume_and_get(inst->dev->dev);
> > > > > +		if (err) {
> > > > > +			dev_err(inst->dev->dev, "decoder runtime resume
> > > > failed %d\n", err);
> > > > > +			ret =3D -EINVAL;
> > > > > +			goto return_buffers;
> > > > > +		}
> > > > > +
> > > > >  		ret =3D wave5_vpu_dec_allocate_ring_buffer(inst);
> > > > >  		if (ret)
> > > > >  			goto return_buffers;
> > > > > diff --git
> > > > > a/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c
> > > > > b/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c
> > > > > index 761775216cd4..ff73d69de41c 100644
> > > > > --- a/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c
> > > > > +++ b/drivers/media/platform/chips-media/wave5/wave5-vpu-enc.c
> > > > > @@ -5,6 +5,7 @@
> > > > >   * Copyright (C) 2021-2023 CHIPS&MEDIA INC
> > > > >   */
> > > > >=20
> > > > > +#include <linux/pm_runtime.h>
> > > > >  #include "wave5-helper.h"
> > > > >=20
> > > > >  #define VPU_ENC_DEV_NAME "C&M Wave5 VPU encoder"
> > > > > @@ -1387,9 +1388,17 @@ static int
> > > > > wave5_vpu_enc_start_streaming(struct
> > > > > vb2_queue *q, unsigned int count
> > > > >=20
> > > > >  	if (inst->state =3D=3D VPU_INST_STATE_NONE && q->type =3D=3D
> > > > V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE) {
> > > > >  		struct enc_open_param open_param;
> > > > > +		int err =3D 0;
> > > > >=20
> > > > >  		memset(&open_param, 0, sizeof(struct enc_open_param));
> > > > >=20
> > > > > +		err =3D pm_runtime_resume_and_get(inst->dev->dev);
> > > > > +		if (err) {
> > > > > +			dev_err(inst->dev->dev, "encoder runtime resume
> > > > failed %d\n", err);
> > > > > +			ret =3D -EINVAL;
> > > > > +			goto return_buffers;
> > > > > +		}
> > > > > +
> > > > >  		wave5_set_enc_openparam(&open_param, inst);
> > > > >=20
> > > > >  		ret =3D wave5_vpu_enc_open(inst, &open_param); diff --
> > git
> > > > > a/drivers/media/platform/chips-media/wave5/wave5-vpu.c
> > > > > b/drivers/media/platform/chips-media/wave5/wave5-vpu.c
> > > > > index 0d90b5820bef..f81409740a56 100644
> > > > > --- a/drivers/media/platform/chips-media/wave5/wave5-vpu.c
> > > > > +++ b/drivers/media/platform/chips-media/wave5/wave5-vpu.c
> > > > > @@ -10,6 +10,7 @@
> > > > >  #include <linux/clk.h>
> > > > >  #include <linux/firmware.h>
> > > > >  #include <linux/interrupt.h>
> > > > > +#include <linux/pm_runtime.h>
> > > > >  #include "wave5-vpu.h"
> > > > >  #include "wave5-regdefine.h"
> > > > >  #include "wave5-vpuconfig.h"
> > > > > @@ -117,6 +118,65 @@ static int wave5_vpu_load_firmware(struct
> > > > > device
> > > > *dev, const char *fw_name,
> > > > >  	return 0;
> > > > >  }
> > > > >=20
> > > > > +static __maybe_unused int wave5_pm_suspend(struct device *dev) {
> > > > > +	struct vpu_device *vpu =3D dev_get_drvdata(dev);
> > > > > +
> > > > > +	if (pm_runtime_suspended(dev))
> > > > > +		return 0;
> > > > > +
> > > > > +	wave5_vpu_sleep_wake(dev, true, NULL, 0);
> > > > > +	clk_bulk_disable_unprepare(vpu->num_clks, vpu->clks);
> > > > > +
> > > > > +	return 0;
> > > > > +}
> > > > > +
> > > > > +static __maybe_unused int wave5_pm_resume(struct device *dev) {
> > > > > +	struct vpu_device *vpu =3D dev_get_drvdata(dev);
> > > > > +	int ret =3D 0;
> > > > > +
> > > > > +	wave5_vpu_sleep_wake(dev, false, NULL, 0);
> > > > > +	ret =3D clk_bulk_prepare_enable(vpu->num_clks, vpu->clks);
> > > > > +	if (ret) {
> > > > > +		dev_err(dev, "Enabling clocks, fail: %d\n", ret);
> > > > > +		return ret;
> > > > > +	}
> > > > > +
> > > > > +	return ret;
> > > > > +}
> > > > > +
> > > > > +static __maybe_unused int wave5_suspend(struct device *dev) {
> > > > > +	struct vpu_device *vpu =3D dev_get_drvdata(dev);
> > > > > +	struct vpu_instance *inst;
> > > > > +
> > > > > +	list_for_each_entry(inst, &vpu->instances, list)
> > > > > +		v4l2_m2m_suspend(inst->v4l2_m2m_dev);
> > > > > +
> > > > > +	return pm_runtime_force_suspend(dev); }
> > > > > +
> > > > > +static __maybe_unused int wave5_resume(struct device *dev) {
> > > > > +	struct vpu_device *vpu =3D dev_get_drvdata(dev);
> > > > > +	struct vpu_instance *inst;
> > > > > +	int ret =3D 0;
> > > > > +
> > > > > +	ret =3D pm_runtime_force_resume(dev);
> > > > > +	if (ret < 0)
> > > > > +		return ret;
> > > > > +
> > > > > +	list_for_each_entry(inst, &vpu->instances, list)
> > > > > +		v4l2_m2m_resume(inst->v4l2_m2m_dev);
> > > > > +
> > > > > +	return ret;
> > > > > +}
> > > >=20
> > > > The functions wave5_suspend() and wave5_resume() are not just
> > > > "maybe_unsued" but actually never used. What was the intention ?
> > > > Considering the usage of __maybe_unused has been such a bad friend
> > > > for this one, could you instead bracket the functions with an
> > explicit ?
> > > >=20
> > > > #ifdef CONFIG_PM
> > > > #endif
> > > >=20
> > > > This way the compiler will have a word if you implement something
> > > > that you forgot to actually use.
> > > >=20
> > > > > +
> > > > > +static const struct dev_pm_ops wave5_pm_ops =3D {
> > > > > +	SET_RUNTIME_PM_OPS(wave5_pm_suspend, wave5_pm_resume,
> > NULL) };
> > > > > +
> > > > >  static int wave5_vpu_probe(struct platform_device *pdev)  {
> > > > >  	int ret;
> > > > > @@ -232,6 +292,10 @@ static int wave5_vpu_probe(struct
> > > > > platform_device
> > > > *pdev)
> > > > >  		 (match_data->flags & WAVE5_IS_DEC) ? "'DECODE'" : "");
> > > > >  	dev_info(&pdev->dev, "Product Code:      0x%x\n", dev-
> > > product_code);
> > > > >  	dev_info(&pdev->dev, "Firmware Revision: %u\n", fw_revision);
> > > > > +
> > > > > +	pm_runtime_enable(&pdev->dev);
> > > > > +	wave5_vpu_sleep_wake(&pdev->dev, true, NULL, 0);
> > > > > +
> > > > >  	return 0;
> > > > >=20
> > > > >  err_enc_unreg:
> > > > > @@ -254,6 +318,9 @@ static int wave5_vpu_remove(struct
> > > > > platform_device
> > > > > *pdev)  {
> > > > >  	struct vpu_device *dev =3D dev_get_drvdata(&pdev->dev);
> > > > >=20
> > > > > +	pm_runtime_put_sync(&pdev->dev);
> > > > > +	pm_runtime_disable(&pdev->dev);
> > > > > +
> > > > >  	mutex_destroy(&dev->dev_lock);
> > > > >  	mutex_destroy(&dev->hw_lock);
> > > > >  	clk_bulk_disable_unprepare(dev->num_clks, dev->clks); @@ -
> > 281,6
> > > > > +348,7 @@ static struct platform_driver wave5_vpu_driver =3D {
> > > > >  	.driver =3D {
> > > > >  		.name =3D VPU_PLATFORM_DEVICE_NAME,
> > > > >  		.of_match_table =3D of_match_ptr(wave5_dt_ids),
> > > > > +		.pm =3D &wave5_pm_ops,
> > > > >  		},
> > > > >  	.probe =3D wave5_vpu_probe,
> > > > >  	.remove =3D wave5_vpu_remove,
> > > > > diff --git
> > > > > a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
> > > > > b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
> > > > > index 1a3efb638dde..f1f8e4fc8474 100644
> > > > > --- a/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
> > > > > +++ b/drivers/media/platform/chips-media/wave5/wave5-vpuapi.c
> > > > > @@ -6,6 +6,7 @@
> > > > >   */
> > > > >=20
> > > > >  #include <linux/bug.h>
> > > > > +#include <linux/pm_runtime.h>
> > > > >  #include "wave5-vpuapi.h"
> > > > >  #include "wave5-regdefine.h"
> > > > >  #include "wave5.h"
> > > > > @@ -232,6 +233,9 @@ int wave5_vpu_dec_close(struct vpu_instance
> > > > > *inst,
> > > > > u32 *fail_res)
> > > > >=20
> > > > >  	wave5_vdi_free_dma_memory(vpu_dev, &p_dec_info->vb_task);
> > > > >=20
> > > > > +	if (!pm_runtime_suspended(inst->dev->dev))
> > > > > +		pm_runtime_put_sync(inst->dev->dev);
> > > > > +
> > > > >  unlock_and_return:
> > > > >  	mutex_unlock(&vpu_dev->hw_lock);
> > > > >=20
> > > > > @@ -734,6 +738,9 @@ int wave5_vpu_enc_close(struct vpu_instance
> > > > > *inst,
> > > > > u32 *fail_res)
> > > > >=20
> > > > >  	wave5_vdi_free_dma_memory(vpu_dev, &p_enc_info->vb_task);
> > > > >=20
> > > > > +	if (!pm_runtime_suspended(inst->dev->dev))
> > > > > +		pm_runtime_put_sync(inst->dev->dev);
> > > >=20
> > > > This seems very unnatural. We do the get() in "start_streaming()",
> > > > but the
> > > > put() is only done when the device is closed, or when the driver is
> > > > removed. As this is not balanced, you seem to have to check the
> > > > suspended condition all over the place.
> > > >=20
> > > > I think we could aim for start_streaming()/stop_streaming() for you=
r
> > > > get/put placement. At least they will be bound to an entirely balan=
ced
> > API.
> > > > But then, a media player in paused sate will prevent that device
> > > > from being suspended.
> > > >=20
> > > > If the HW is capable of preserving enough state, and From the short
> > > > doc I have it gives me the impression it can preserve that, I'd
> > > > suggest to follow what hantro driver is doing. What is does is that
> > > > it will do get() in device_run(), and put() whenever the job
> > > > completes. This driver has been designed so when there is no job, i=
t
> > > > means the firmware is currently idle and looking for more work. So
> > > > it seems like the perfect moment to do suspend it.
> > > >=20
> > > > Nicolas
> > > >=20
> > > > > +
> > > > >  	mutex_unlock(&vpu_dev->hw_lock);
> > > > >=20
> > > > >  	return 0;
> > > > > diff --git a/drivers/media/platform/chips-media/wave5/wave5.h
> > > > > b/drivers/media/platform/chips-media/wave5/wave5.h
> > > > > index 063028eccd3b..6125eff938a8 100644
> > > > > --- a/drivers/media/platform/chips-media/wave5/wave5.h
> > > > > +++ b/drivers/media/platform/chips-media/wave5/wave5.h
> > > > > @@ -56,6 +56,9 @@ int wave5_vpu_get_version(struct vpu_device
> > > > > *vpu_dev, u32 *revision);
> > > > >=20
> > > > >  int wave5_vpu_init(struct device *dev, u8 *fw, size_t size);
> > > > >=20
> > > > > +int wave5_vpu_sleep_wake(struct device *dev, bool i_sleep_wake,
> > > > > +const
> > > > uint16_t *code,
> > > > > +			 size_t size);
> > > > > +
> > > > >  int wave5_vpu_reset(struct device *dev, enum sw_reset_mode
> > > > > reset_mode);
> > > > >=20
> > > > >  int wave5_vpu_build_up_dec_param(struct vpu_instance *inst,
> > > > > struct dec_open_param *param);
> > >=20
>=20