Message-ID:
 <SE1P216MB1303932A0D3FC399179115D9ED572@SE1P216MB1303.KORP216.PROD.OUTLOOK.COM>
Date: Wed, 21 Feb 2024 02:27:50 +0000
From: jackson.lee <jackson.lee@...psnmedia.com>
To: Nicolas Dufresne <nicolas@...fresne.ca>, "mchehab@...nel.org"
	<mchehab@...nel.org>, "linux-media@...r.kernel.org"
	<linux-media@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, Nas Chung <nas.chung@...psnmedia.com>
CC: lafley.kim <lafley.kim@...psnmedia.com>, "b-brnich@...com"
	<b-brnich@...com>
Subject: RE: [RESEND PATCH v0 3/5] wave5 : Support runtime suspend/resume.

Hello Nicolas


Thanks for your comment

> Le mardi 20 février 2024 à 05:12 +0000, jackson.lee a écrit :
> > A pause is common state for media player, but our VPU could trigger an
> interrupt 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
> through the comments, and reply to them underneath so we can have a proper
> discussion.
> 
> In our experience, and with the rework of the driver we did during up-
> streaming, there is no more un-solicited IRQ. The way the driver state
> machine has been built, when the m2m framework is idle (no jobs are active
> or pending), it means 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 place 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 to
> device_run() to be called again, and it would be a good place to resume it.

The above comment means like the below ?
The wave5_vpu_dec_finish_decode is called by IRQ if there is a decoded frame.
And at the end of the function, if there is no data queued, v4l2_m2m_job_finish is called.
You means suspend is called in that function and if app feeds new data into v4l2 driver, the device_run then is called,
In the device_run, resume is called.


I have a question, 
If app is paused or resumed , the v4l2's vidioc_decoder_cmd is always called ?

Thanks.


> 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 small 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
> application can endup disabling the kernel ability to save power.
> Personally, I think we 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
> 
> >
> > Thanks.
> >
> > > Le lundi 19 février 2024 à 04:04 +0000, jackson.lee a écrit :
> > > > Hi Nicolas
> > > >
> > > >
> > > > > 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.
> > > > >
> > > > > I think we could aim for start_streaming()/stop_streaming() for
> > > > > your get/put placement. At least they will be bound to an
> > > > > entirely balanced
> > > API.
> > > > > But then, a media player in paused sate will prevent that device
> > > > > from being suspended.
> > > > >
> > > > > 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, it means the firmware is currently idle
> > > > > and looking for more work. So it seems like the perfect moment to
> do suspend it.
> > > > >
> > > >
> > > > Thanks your comment,
> > > >
> > > > Currently they are not balanced,
> > > > If we puts "the put functon" into the stop_streaming, our hw is
> > > > stalled
> > > 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.
> > > >
> > > >
> > > > @@ -1867,6 +1868,13 @@ static int wave5_vpu_open_dec(struct file
> > > > *filp)
> > > >
> > > >         wave5_vdi_allocate_sram(inst->dev);
> > > >
> > > > +       err = pm_runtime_resume_and_get(inst->dev->dev);
> > > > +       if (err) {
> > > > +               dev_err(inst->dev->dev, "decoder runtime resume
> > > failed %d\n", err);
> > > > +               ret = -EINVAL;
> > > > +               goto cleanup_inst;
> > > > +       }
> > > > +
> > > >         return 0;
> > >
> > > I guess we need to discuss the power management strategy for this
> device.
> > > If you do resume_and_get() in open(), and then put in close(), that
> > > seems 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 background, you still keep the IP running. This is
> > > extremely common, since application cannot close their device
> > > without loosing the reference frames, and thus having to do extra
> > > work on resume to seek back to the previous sync point and drop
> unneeded frames.
> > >
> > > 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 firt place.
> > > If we are to suspend only when there is no meaningful state, we
> > > could just free all resources and power it off completely. (This is
> > > just for illustration, its probably to slow to boot the firmware at
> > > runtime)
> > >
> > >
> > > I understand you suffered lockup with a start_streaming() for
> > > resume_and_get(), and stop_streaming() for put(), this may simply
> > > indicate that some hardware access are needed between these two. Can
> > > you write down a power management plan that would effectively save
> > > power in common use cases ? We can certainly help in refactoring the
> code to make that happen.
> > >
> > > Nicolas
> > >
> > > >
> > > > > Le mercredi 31 janvier 2024 à 10:30 +0900, jackson.lee a écrit :
> > > > > > 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);
> > > > >
> > > > > I wonder how useful is it to teach everyone what the generic
> > > > > 'struct dev_pm_ops'
> > > > > contains. Perhaps you simply wanted that this patch implement
> > > > > both suspend and resume ops ?
> > > > >
> > > > > >
> > > > > > Signed-off-by: Jackson Lee <jackson.lee@...psnmedia.com>
> > > > > > Signed-off-by: Nas Chung <nas.chung@...psnmedia.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(-)
> > > > > >
> > > > > > 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);
> > > > >
> > > > > In some way, the relation between suspend and this register
> > > > > write is 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).
> > > > >
> > > > > >
> > > > > >  	ret = send_firmware_command(inst, W5_CREATE_INSTANCE, true,
> > > > > > NULL,
> > > > > NULL);
> > > > > >  	if (ret) {
> > > > > > @@ -1075,8 +1076,8 @@ int wave5_vpu_re_init(struct device
> > > > > > *dev, u8 *fw,
> > > > > size_t size)
> > > > > >  	return setup_wave5_properties(dev);  }
> > > > > >
> > > > > > -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
> > > > > >   */
> > > > > >
> > > > > > +#include <linux/pm_runtime.h>
> > > > > >  #include "wave5-helper.h"
> > > > > >
> > > > > >  #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
> > > > > >
> > > > > >  	if (q->type == V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE && inst-
> > > > state
> > > > > > ==
> > > > > VPU_INST_STATE_NONE) {
> > > > > >  		struct dec_open_param open_param;
> > > > > > +		int err = 0;
> > > > > >
> > > > > >  		memset(&open_param, 0, sizeof(struct dec_open_param));
> > > > > >
> > > > > > +		err = pm_runtime_resume_and_get(inst->dev->dev);
> > > > > > +		if (err) {
> > > > > > +			dev_err(inst->dev->dev, "decoder runtime resume
> > > > > failed %d\n", err);
> > > > > > +			ret = -EINVAL;
> > > > > > +			goto return_buffers;
> > > > > > +		}
> > > > > > +
> > > > > >  		ret = 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
> > > > > >   */
> > > > > >
> > > > > > +#include <linux/pm_runtime.h>
> > > > > >  #include "wave5-helper.h"
> > > > > >
> > > > > >  #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
> > > > > >
> > > > > >  	if (inst->state == VPU_INST_STATE_NONE && q->type ==
> > > > > V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE) {
> > > > > >  		struct enc_open_param open_param;
> > > > > > +		int err = 0;
> > > > > >
> > > > > >  		memset(&open_param, 0, sizeof(struct enc_open_param));
> > > > > >
> > > > > > +		err = pm_runtime_resume_and_get(inst->dev->dev);
> > > > > > +		if (err) {
> > > > > > +			dev_err(inst->dev->dev, "encoder runtime resume
> > > > > failed %d\n", err);
> > > > > > +			ret = -EINVAL;
> > > > > > +			goto return_buffers;
> > > > > > +		}
> > > > > > +
> > > > > >  		wave5_set_enc_openparam(&open_param, inst);
> > > > > >
> > > > > >  		ret = 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;
> > > > > >  }
> > > > > >
> > > > > > +static __maybe_unused int wave5_pm_suspend(struct device *dev)
> {
> > > > > > +	struct vpu_device *vpu = 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 = dev_get_drvdata(dev);
> > > > > > +	int ret = 0;
> > > > > > +
> > > > > > +	wave5_vpu_sleep_wake(dev, false, NULL, 0);
> > > > > > +	ret = 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 = 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 = dev_get_drvdata(dev);
> > > > > > +	struct vpu_instance *inst;
> > > > > > +	int ret = 0;
> > > > > > +
> > > > > > +	ret = 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;
> > > > > > +}
> > > > >
> > > > > 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 ?
> > > > >
> > > > > #ifdef CONFIG_PM
> > > > > #endif
> > > > >
> > > > > This way the compiler will have a word if you implement
> > > > > something that you forgot to actually use.
> > > > >
> > > > > > +
> > > > > > +static const struct dev_pm_ops wave5_pm_ops = {
> > > > > > +	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;
> > > > > >
> > > > > >  err_enc_unreg:
> > > > > > @@ -254,6 +318,9 @@ static int wave5_vpu_remove(struct
> > > > > > platform_device
> > > > > > *pdev)  {
> > > > > >  	struct vpu_device *dev = dev_get_drvdata(&pdev->dev);
> > > > > >
> > > > > > +	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 = {
> > > > > >  	.driver = {
> > > > > >  		.name = VPU_PLATFORM_DEVICE_NAME,
> > > > > >  		.of_match_table = of_match_ptr(wave5_dt_ids),
> > > > > > +		.pm = &wave5_pm_ops,
> > > > > >  		},
> > > > > >  	.probe = wave5_vpu_probe,
> > > > > >  	.remove = 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 @@
> > > > > >   */
> > > > > >
> > > > > >  #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)
> > > > > >
> > > > > >  	wave5_vdi_free_dma_memory(vpu_dev, &p_dec_info->vb_task);
> > > > > >
> > > > > > +	if (!pm_runtime_suspended(inst->dev->dev))
> > > > > > +		pm_runtime_put_sync(inst->dev->dev);
> > > > > > +
> > > > > >  unlock_and_return:
> > > > > >  	mutex_unlock(&vpu_dev->hw_lock);
> > > > > >
> > > > > > @@ -734,6 +738,9 @@ int wave5_vpu_enc_close(struct
> > > > > > vpu_instance *inst,
> > > > > > u32 *fail_res)
> > > > > >
> > > > > >  	wave5_vdi_free_dma_memory(vpu_dev, &p_enc_info->vb_task);
> > > > > >
> > > > > > +	if (!pm_runtime_suspended(inst->dev->dev))
> > > > > > +		pm_runtime_put_sync(inst->dev->dev);
> > > > >
> > > > > 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.
> > > > >
> > > > > I think we could aim for start_streaming()/stop_streaming() for
> > > > > your get/put placement. At least they will be bound to an
> > > > > entirely balanced
> > > API.
> > > > > But then, a media player in paused sate will prevent that device
> > > > > from being suspended.
> > > > >
> > > > > 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, it means the firmware is currently idle
> > > > > and looking for more work. So it seems like the perfect moment to
> do suspend it.
> > > > >
> > > > > Nicolas
> > > > >
> > > > > > +
> > > > > >  	mutex_unlock(&vpu_dev->hw_lock);
> > > > > >
> > > > > >  	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);
> > > > > >
> > > > > >  int wave5_vpu_init(struct device *dev, u8 *fw, size_t size);
> > > > > >
> > > > > > +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);
> > > > > >
> > > > > >  int wave5_vpu_build_up_dec_param(struct vpu_instance *inst,
> > > > > > struct dec_open_param *param);
> > > >
> >

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