Re: [RFC v2 1/1] drm/lima: Add optional devfreq support

[Robin Murphy]

Hi Martin,

On 2019-12-27 5:37 pm, Martin Blumenstingl wrote:
> Most platforms with a Mali-400 or Mali-450 GPU also have support for
> changing the GPU clock frequency. Add devfreq support so the GPU clock
> rate is updated based on the actual GPU usage when the
> "operating-points-v2" property is present in the board.dts.
>
> The actual devfreq code is taken from panfrost_devfreq.c and modified so
> it matches what the lima hardware needs:
> - a call to dev_pm_opp_set_clkname() during initialization because there
>    are two clocks on Mali-4x0 IPs. "core" is the one that actually clocks
>    the GPU so we need to control it using devfreq.
> - locking when reading or writing the devfreq statistics because (unlike
>    than panfrost) we have multiple PP and GP IRQs which may finish jobs
>    concurrently.

I gave this a quick try on my RK3328, and the clock scaling indeed kicks 
in nicely on the glmark2 scenes that struggle, however something appears 
to be missing in terms of regulator association, as the appropriate OPP 
voltages aren't reflected in the GPU supply (fortunately the initial 
voltage seems close enough to that of the highest OPP not to cause major 
problems, on my box at least). With panfrost on RK3399 I do see the 
supply voltage scaling accordingly, but I don't know my way around 
devfreq well enough to know what matters in the difference :/

Thanks,
Robin.

> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> ---
>   drivers/gpu/drm/lima/Kconfig        |   1 +
>   drivers/gpu/drm/lima/Makefile       |   3 +-
>   drivers/gpu/drm/lima/lima_devfreq.c | 183 ++++++++++++++++++++++++++++
>   drivers/gpu/drm/lima/lima_devfreq.h |  15 +++
>   drivers/gpu/drm/lima/lima_device.c  |   4 +
>   drivers/gpu/drm/lima/lima_device.h  |  17 +++
>   drivers/gpu/drm/lima/lima_drv.c     |  14 ++-
>   drivers/gpu/drm/lima/lima_sched.c   |   7 ++
>   drivers/gpu/drm/lima/lima_sched.h   |   3 +
>   9 files changed, 244 insertions(+), 3 deletions(-)
>   create mode 100644 drivers/gpu/drm/lima/lima_devfreq.c
>   create mode 100644 drivers/gpu/drm/lima/lima_devfreq.h
>
> diff --git a/drivers/gpu/drm/lima/Kconfig b/drivers/gpu/drm/lima/Kconfig
> index 571dc369a7e9..cdd24b68b5d4 100644
> --- a/drivers/gpu/drm/lima/Kconfig
> +++ b/drivers/gpu/drm/lima/Kconfig
> @@ -10,5 +10,6 @@ config DRM_LIMA
>          depends on OF
>          select DRM_SCHED
>          select DRM_GEM_SHMEM_HELPER
> +       select PM_DEVFREQ
>          help
>            DRM driver for ARM Mali 400/450 GPUs.
> diff --git a/drivers/gpu/drm/lima/Makefile b/drivers/gpu/drm/lima/Makefile
> index a85444b0a1d4..5e5c29875e9c 100644
> --- a/drivers/gpu/drm/lima/Makefile
> +++ b/drivers/gpu/drm/lima/Makefile
> @@ -14,6 +14,7 @@ lima-y := \
>   	lima_sched.o \
>   	lima_ctx.o \
>   	lima_dlbu.o \
> -	lima_bcast.o
> +	lima_bcast.o \
> +	lima_devfreq.o
>   
>   obj-$(CONFIG_DRM_LIMA) += lima.o
> diff --git a/drivers/gpu/drm/lima/lima_devfreq.c b/drivers/gpu/drm/lima/lima_devfreq.c
> new file mode 100644
> index 000000000000..a5fd6b8faa77
> --- /dev/null
> +++ b/drivers/gpu/drm/lima/lima_devfreq.c
> @@ -0,0 +1,183 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2019 Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> + *
> + * Based on panfrost_devfreq.c:
> + *   Copyright 2019 Collabora ltd.
> + */
> +#include <linux/clk.h>
> +#include <linux/devfreq.h>
> +#include <linux/devfreq_cooling.h>
> +#include <linux/device.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_opp.h>
> +
> +#include "lima_device.h"
> +#include "lima_devfreq.h"
> +
> +static void lima_devfreq_update_utilization(struct lima_device *ldev)
> +{
> +	unsigned long irqflags;
> +	ktime_t now, last;
> +
> +	if (!ldev->devfreq.devfreq)
> +		return;
> +
> +	spin_lock_irqsave(&ldev->devfreq.lock, irqflags);
> +
> +	now = ktime_get();
> +	last = ldev->devfreq.time_last_update;
> +
> +	if (atomic_read(&ldev->devfreq.busy_count) > 0)
> +		ldev->devfreq.busy_time += ktime_sub(now, last);
> +	else
> +		ldev->devfreq.idle_time += ktime_sub(now, last);
> +
> +	ldev->devfreq.time_last_update = now;
> +
> +	spin_unlock_irqrestore(&ldev->devfreq.lock, irqflags);
> +}
> +
> +static int lima_devfreq_target(struct device *dev, unsigned long *freq,
> +			       u32 flags)
> +{
> +	struct dev_pm_opp *opp;
> +	int err;
> +
> +	opp = devfreq_recommended_opp(dev, freq, flags);
> +	if (IS_ERR(opp))
> +		return PTR_ERR(opp);
> +	dev_pm_opp_put(opp);
> +
> +	err = dev_pm_opp_set_rate(dev, *freq);
> +	if (err)
> +		return err;
> +
> +	return 0;
> +}
> +
> +static void lima_devfreq_reset(struct lima_device *ldev)
> +{
> +	unsigned long irqflags;
> +
> +	spin_lock_irqsave(&ldev->devfreq.lock, irqflags);
> +
> +	ldev->devfreq.busy_time = 0;
> +	ldev->devfreq.idle_time = 0;
> +	ldev->devfreq.time_last_update = ktime_get();
> +
> +	spin_unlock_irqrestore(&ldev->devfreq.lock, irqflags);
> +}
> +
> +static int lima_devfreq_get_dev_status(struct device *dev,
> +				       struct devfreq_dev_status *status)
> +{
> +	struct lima_device *ldev = dev_get_drvdata(dev);
> +	unsigned long irqflags;
> +
> +	lima_devfreq_update_utilization(ldev);
> +
> +	status->current_frequency = clk_get_rate(ldev->clk_gpu);
> +
> +	spin_lock_irqsave(&ldev->devfreq.lock, irqflags);
> +
> +	status->total_time = ktime_to_ns(ktime_add(ldev->devfreq.busy_time,
> +						   ldev->devfreq.idle_time));
> +	status->busy_time = ktime_to_ns(ldev->devfreq.busy_time);
> +
> +	spin_unlock_irqrestore(&ldev->devfreq.lock, irqflags);
> +
> +	lima_devfreq_reset(ldev);
> +
> +	dev_dbg(ldev->dev, "busy %lu total %lu %lu %% freq %lu MHz\n",
> +		status->busy_time, status->total_time,
> +		status->busy_time / (status->total_time / 100),
> +		status->current_frequency / 1000 / 1000);
> +
> +	return 0;
> +}
> +
> +static struct devfreq_dev_profile lima_devfreq_profile = {
> +	.polling_ms = 50, /* ~3 frames */
> +	.target = lima_devfreq_target,
> +	.get_dev_status = lima_devfreq_get_dev_status,
> +};
> +
> +int lima_devfreq_init(struct lima_device *ldev)
> +{
> +	struct thermal_cooling_device *cooling;
> +	struct device *dev = &ldev->pdev->dev;
> +	struct devfreq *devfreq;
> +	struct dev_pm_opp *opp;
> +	unsigned long cur_freq;
> +	int ret;
> +
> +	spin_lock_init(&ldev->devfreq.lock);
> +
> +	ldev->devfreq.opp_table = dev_pm_opp_set_clkname(dev, "core");
> +	if (IS_ERR(ldev->devfreq.opp_table))
> +		return PTR_ERR(ldev->devfreq.opp_table);
> +
> +	ret = dev_pm_opp_of_add_table(dev);
> +	if (ret == -ENODEV) /* Optional, continue without devfreq */
> +		return 0;
> +	else if (ret)
> +		return ret;
> +
> +	lima_devfreq_reset(ldev);
> +
> +	cur_freq = clk_get_rate(ldev->clk_gpu);
> +
> +	opp = devfreq_recommended_opp(dev, &cur_freq, 0);
> +	if (IS_ERR(opp))
> +		return PTR_ERR(opp);
> +
> +	lima_devfreq_profile.initial_freq = cur_freq;
> +	dev_pm_opp_put(opp);
> +
> +	devfreq = devm_devfreq_add_device(dev, &lima_devfreq_profile,
> +					  DEVFREQ_GOV_SIMPLE_ONDEMAND, NULL);
> +	if (IS_ERR(devfreq)) {
> +		dev_err(dev, "Couldn't initialize GPU devfreq\n");
> +		dev_pm_opp_of_remove_table(dev);
> +		return PTR_ERR(devfreq);
> +	}
> +
> +	ldev->devfreq.devfreq = devfreq;
> +
> +	cooling = of_devfreq_cooling_register(dev->of_node, devfreq);
> +	if (IS_ERR(cooling))
> +		dev_info(dev, "Failed to register cooling device\n");
> +	else
> +		ldev->devfreq.cooling = cooling;
> +
> +	return 0;
> +}
> +
> +void lima_devfreq_fini(struct lima_device *ldev)
> +{
> +	if (ldev->devfreq.cooling)
> +		devfreq_cooling_unregister(ldev->devfreq.cooling);
> +
> +	if (ldev->devfreq.opp_table) {
> +		dev_pm_opp_put_clkname(ldev->devfreq.opp_table);
> +		ldev->devfreq.opp_table = NULL;
> +	}
> +
> +	dev_pm_opp_of_remove_table(&ldev->pdev->dev);
> +}
> +
> +void lima_devfreq_record_busy(struct lima_device *ldev)
> +{
> +	lima_devfreq_update_utilization(ldev);
> +	atomic_inc(&ldev->devfreq.busy_count);
> +}
> +
> +void lima_devfreq_record_idle(struct lima_device *ldev)
> +{
> +	int count;
> +
> +	lima_devfreq_update_utilization(ldev);
> +	count = atomic_dec_if_positive(&ldev->devfreq.busy_count);
> +	WARN_ON(count < 0);
> +}
> diff --git a/drivers/gpu/drm/lima/lima_devfreq.h b/drivers/gpu/drm/lima/lima_devfreq.h
> new file mode 100644
> index 000000000000..fe4f8a437033
> --- /dev/null
> +++ b/drivers/gpu/drm/lima/lima_devfreq.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright 2019 Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx> */
> +
> +#ifndef __LIMA_DEVFREQ_H__
> +#define __LIMA_DEVFREQ_H__
> +
> +struct lima_device;
> +
> +int lima_devfreq_init(struct lima_device *ldev);
> +void lima_devfreq_fini(struct lima_device *ldev);
> +
> +void lima_devfreq_record_busy(struct lima_device *ldev);
> +void lima_devfreq_record_idle(struct lima_device *ldev);
> +
> +#endif
> diff --git a/drivers/gpu/drm/lima/lima_device.c b/drivers/gpu/drm/lima/lima_device.c
> index 19829b543024..7f1f7a1c03e5 100644
> --- a/drivers/gpu/drm/lima/lima_device.c
> +++ b/drivers/gpu/drm/lima/lima_device.c
> @@ -214,6 +214,8 @@ static int lima_init_gp_pipe(struct lima_device *dev)
>   	struct lima_sched_pipe *pipe = dev->pipe + lima_pipe_gp;
>   	int err;
>   
> +	pipe->ldev = dev;
> +
>   	err = lima_sched_pipe_init(pipe, "gp");
>   	if (err)
>   		return err;
> @@ -244,6 +246,8 @@ static int lima_init_pp_pipe(struct lima_device *dev)
>   	struct lima_sched_pipe *pipe = dev->pipe + lima_pipe_pp;
>   	int err, i;
>   
> +	pipe->ldev = dev;
> +
>   	err = lima_sched_pipe_init(pipe, "pp");
>   	if (err)
>   		return err;
> diff --git a/drivers/gpu/drm/lima/lima_device.h b/drivers/gpu/drm/lima/lima_device.h
> index 31158d86271c..26f0efdd17f1 100644
> --- a/drivers/gpu/drm/lima/lima_device.h
> +++ b/drivers/gpu/drm/lima/lima_device.h
> @@ -5,6 +5,7 @@
>   #define __LIMA_DEVICE_H__
>   
>   #include <drm/drm_device.h>
> +#include <linux/atomic.h>
>   #include <linux/delay.h>
>   
>   #include "lima_sched.h"
> @@ -94,6 +95,22 @@ struct lima_device {
>   
>   	u32 *dlbu_cpu;
>   	dma_addr_t dlbu_dma;
> +
> +	struct {
> +		struct devfreq *devfreq;
> +		struct opp_table *opp_table;
> +		struct thermal_cooling_device *cooling;
> +		ktime_t busy_time;
> +		ktime_t idle_time;
> +		ktime_t time_last_update;
> +		atomic_t busy_count;
> +		/*
> +		 * Protect busy_time, idle_time and time_last_update because
> +		 * these can be updated concurrently - for example by the GP
> +		 * and PP interrupts.
> +		 */
> +		spinlock_t lock;
> +	} devfreq;
>   };
>   
>   static inline struct lima_device *
> diff --git a/drivers/gpu/drm/lima/lima_drv.c b/drivers/gpu/drm/lima/lima_drv.c
> index 124efe4fa97b..b64b1777f220 100644
> --- a/drivers/gpu/drm/lima/lima_drv.c
> +++ b/drivers/gpu/drm/lima/lima_drv.c
> @@ -10,6 +10,7 @@
>   #include <drm/drm_prime.h>
>   #include <drm/lima_drm.h>
>   
> +#include "lima_devfreq.h"
>   #include "lima_drv.h"
>   #include "lima_gem.h"
>   #include "lima_vm.h"
> @@ -296,18 +297,26 @@ static int lima_pdev_probe(struct platform_device *pdev)
>   	if (err)
>   		goto err_out1;
>   
> +	err = lima_devfreq_init(ldev);
> +	if (err) {
> +		dev_err(&pdev->dev, "Fatal error during devfreq init\n");
> +		goto err_out2;
> +	}
> +
>   	/*
>   	 * Register the DRM device with the core and the connectors with
>   	 * sysfs.
>   	 */
>   	err = drm_dev_register(ddev, 0);
>   	if (err < 0)
> -		goto err_out2;
> +		goto err_out3;
>   
>   	return 0;
>   
> -err_out2:
> +err_out3:
>   	lima_device_fini(ldev);
> +err_out2:
> +	lima_devfreq_fini(ldev);
>   err_out1:
>   	drm_dev_put(ddev);
>   err_out0:
> @@ -321,6 +330,7 @@ static int lima_pdev_remove(struct platform_device *pdev)
>   	struct drm_device *ddev = ldev->ddev;
>   
>   	drm_dev_unregister(ddev);
> +	lima_devfreq_fini(ldev);
>   	lima_device_fini(ldev);
>   	drm_dev_put(ddev);
>   	lima_sched_slab_fini();
> diff --git a/drivers/gpu/drm/lima/lima_sched.c b/drivers/gpu/drm/lima/lima_sched.c
> index f522c5f99729..851c496a168b 100644
> --- a/drivers/gpu/drm/lima/lima_sched.c
> +++ b/drivers/gpu/drm/lima/lima_sched.c
> @@ -5,6 +5,7 @@
>   #include <linux/slab.h>
>   #include <linux/xarray.h>
>   
> +#include "lima_devfreq.h"
>   #include "lima_drv.h"
>   #include "lima_sched.h"
>   #include "lima_vm.h"
> @@ -213,6 +214,8 @@ static struct dma_fence *lima_sched_run_job(struct drm_sched_job *job)
>   	 */
>   	ret = dma_fence_get(task->fence);
>   
> +	lima_devfreq_record_busy(pipe->ldev);
> +
>   	pipe->current_task = task;
>   
>   	/* this is needed for MMU to work correctly, otherwise GP/PP
> @@ -280,6 +283,8 @@ static void lima_sched_handle_error_task(struct lima_sched_pipe *pipe,
>   	pipe->current_vm = NULL;
>   	pipe->current_task = NULL;
>   
> +	lima_devfreq_record_idle(pipe->ldev);
> +
>   	drm_sched_resubmit_jobs(&pipe->base);
>   	drm_sched_start(&pipe->base, true);
>   }
> @@ -348,6 +353,8 @@ void lima_sched_pipe_fini(struct lima_sched_pipe *pipe)
>   
>   void lima_sched_pipe_task_done(struct lima_sched_pipe *pipe)
>   {
> +	lima_devfreq_record_idle(pipe->ldev);
> +
>   	if (pipe->error)
>   		schedule_work(&pipe->error_work);
>   	else {
> diff --git a/drivers/gpu/drm/lima/lima_sched.h b/drivers/gpu/drm/lima/lima_sched.h
> index 928af91c1118..9ae7df7d7fbb 100644
> --- a/drivers/gpu/drm/lima/lima_sched.h
> +++ b/drivers/gpu/drm/lima/lima_sched.h
> @@ -6,6 +6,7 @@
>   
>   #include <drm/gpu_scheduler.h>
>   
> +struct lima_device;
>   struct lima_vm;
>   
>   struct lima_sched_task {
> @@ -41,6 +42,8 @@ struct lima_sched_pipe {
>   	u32 fence_seqno;
>   	spinlock_t fence_lock;
>   
> +	struct lima_device *ldev;
> +
>   	struct lima_sched_task *current_task;
>   	struct lima_vm *current_vm;
>