Re: [RFC v2 3/8] drm/panthor: Add panthor_perf_init and panthor_perf_unplug

[Lukas Zapolskas <lukas.zapolskas@arm.com>]

(please excuse the line-wrapping on the previous email,
it seems that it was soft-wrapped).

On 27/01/2025 12:46, Adrián Larumbe wrote:
> On 11.12.2024 16:50, Lukas Zapolskas wrote:
>> Added the panthor_perf system initialization and unplug code to allow
>> for the handling of userspace sessions to be added in follow-up patches.
>>
>> Signed-off-by: Lukas Zapolskas <lukas.zapolskas@arm.com>
>> ---
>>   drivers/gpu/drm/panthor/panthor_device.c |  7 +++
>>   drivers/gpu/drm/panthor/panthor_device.h |  5 +-
>>   drivers/gpu/drm/panthor/panthor_perf.c   | 77 ++++++++++++++++++++++++
>>   drivers/gpu/drm/panthor/panthor_perf.h   |  3 +
>>   4 files changed, 91 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
>> index 00f7b8ce935a..1a81a436143b 100644
>> --- a/drivers/gpu/drm/panthor/panthor_device.c
>> +++ b/drivers/gpu/drm/panthor/panthor_device.c
>> @@ -19,6 +19,7 @@
>>   #include "panthor_fw.h"
>>   #include "panthor_gpu.h"
>>   #include "panthor_mmu.h"
>> +#include "panthor_perf.h"
>>   #include "panthor_regs.h"
>>   #include "panthor_sched.h"
>>   
>> @@ -97,6 +98,7 @@ void panthor_device_unplug(struct panthor_device *ptdev)
>>   	/* Now, try to cleanly shutdown the GPU before the device resources
>>   	 * get reclaimed.
>>   	 */
>> +	panthor_perf_unplug(ptdev);
>>   	panthor_sched_unplug(ptdev);
>>   	panthor_fw_unplug(ptdev);
>>   	panthor_mmu_unplug(ptdev);
>> @@ -262,6 +264,10 @@ int panthor_device_init(struct panthor_device *ptdev)
>>   	if (ret)
>>   		goto err_unplug_fw;
>>   
>> +	ret = panthor_perf_init(ptdev);
>> +	if (ret)
>> +		goto err_unplug_fw;
>> +
>>   	/* ~3 frames */
>>   	pm_runtime_set_autosuspend_delay(ptdev->base.dev, 50);
>>   	pm_runtime_use_autosuspend(ptdev->base.dev);
>> @@ -275,6 +281,7 @@ int panthor_device_init(struct panthor_device *ptdev)
>>   
>>   err_disable_autosuspend:
>>   	pm_runtime_dont_use_autosuspend(ptdev->base.dev);
>> +	panthor_perf_unplug(ptdev);
>>   	panthor_sched_unplug(ptdev);
>>   
>>   err_unplug_fw:
>> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
>> index 636542c1dcbd..aca33d03036c 100644
>> --- a/drivers/gpu/drm/panthor/panthor_device.h
>> +++ b/drivers/gpu/drm/panthor/panthor_device.h
>> @@ -26,7 +26,7 @@ struct panthor_heap_pool;
>>   struct panthor_job;
>>   struct panthor_mmu;
>>   struct panthor_fw;
>> -struct panthor_perfcnt;
>> +struct panthor_perf;
>>   struct panthor_vm;
>>   struct panthor_vm_pool;
>>   
>> @@ -137,6 +137,9 @@ struct panthor_device {
>>   	/** @devfreq: Device frequency scaling management data. */
>>   	struct panthor_devfreq *devfreq;
>>   
>> +	/** @perf: Performance counter management data. */
>> +	struct panthor_perf *perf;
>> +
>>   	/** @unplug: Device unplug related fields. */
>>   	struct {
>>   		/** @lock: Lock used to serialize unplug operations. */
>> diff --git a/drivers/gpu/drm/panthor/panthor_perf.c b/drivers/gpu/drm/panthor/panthor_perf.c
>> index 0e3d769c1805..e0dc6c4b0cf1 100644
>> --- a/drivers/gpu/drm/panthor/panthor_perf.c
>> +++ b/drivers/gpu/drm/panthor/panthor_perf.c
>> @@ -13,6 +13,24 @@
>>   #include "panthor_perf.h"
>>   #include "panthor_regs.h"
>>   
>> +struct panthor_perf {
>> +	/**
>> +	 * @block_set: The global counter set configured onto the HW.
>> +	 */
>> +	u8 block_set;
> 
> I think this field is not used in any further patches. Only in the sampler
> struct definition later on you include the same field and assign it from
> the ioctl setup arguments.

Will have to correct that, it should be used for the FW programming and
checking whether a session creation request can be satisfied.

> 
>> +	/** @next_session: The ID of the next session. */
>> +	u32 next_session;
>> +
>> +	/** @session_range: The number of sessions supported at a time. */
>> +	struct xa_limit session_range;
>> +
>> +	/**
>> +	 * @sessions: Global map of sessions, accessed by their ID.
>> +	 */
>> +	struct xarray sessions;
>> +};
>> +
>>   /**
>>    * PANTHOR_PERF_COUNTERS_PER_BLOCK - On CSF architectures pre-11.x, the number of counters
>>    * per block was hardcoded to be 64. Arch 11.0 onwards supports the PRFCNT_FEATURES GPU register,
>> @@ -45,3 +63,62 @@ void panthor_perf_info_init(struct panthor_device *ptdev)
>>   	perf_info->shader_blocks = hweight64(ptdev->gpu_info.shader_present);
>>   }
>>   
>> +/**
>> + * panthor_perf_init - Initialize the performance counter subsystem.
>> + * @ptdev: Panthor device
>> + *
>> + * The performance counters require the FW interface to be available to setup the
>> + * sampling ringbuffers, so this must be called only after FW is initialized.
>> + *
>> + * Return: 0 on success, negative error code on failure.
>> + */
>> +int panthor_perf_init(struct panthor_device *ptdev)
>> +{
>> +	struct panthor_perf *perf;
>> +
>> +	if (!ptdev)
>> +		return -EINVAL;
>> +
>> +	perf = devm_kzalloc(ptdev->base.dev, sizeof(*perf), GFP_KERNEL);
>> +	if (ZERO_OR_NULL_PTR(perf))
>> +		return -ENOMEM;
>> +
>> +	xa_init_flags(&perf->sessions, XA_FLAGS_ALLOC);
>> +
>> +	/* Currently, we only support a single session at a time. */
>> +	perf->session_range = (struct xa_limit) {
>> +		.min = 0,
>> +		.max = 1,
>> +	};
> 
> I guess at the moment we only allow a single session because periodic sampling
> isn't yet implemented. Does that mean multisession support will not be made
> available for manual samplers in the future?

The RFC was intended to purely give a functional implementation without
periodic or multi-client sampling. Multi-client will be available for
both periodic and manual sessions, once periodic is implemented.

>> +
>> +	drm_info(&ptdev->base, "Performance counter subsystem initialized");
>> +
>> +	ptdev->perf = perf;
>> +
>> +	return 0;
>> +}
>> +
>> +/**
>> + * panthor_perf_unplug - Terminate the performance counter subsystem.
>> + * @ptdev: Panthor device.
>> + *
>> + * This function will terminate the performance counter control structures and any remaining
>> + * sessions, after waiting for any pending interrupts.
>> + */
>> +void panthor_perf_unplug(struct panthor_device *ptdev)
>> +{
>> +	struct panthor_perf *perf = ptdev->perf;
>> +
>> +	if (!perf)
>> +		return;
>> +
>> +	if (!xa_empty(&perf->sessions))
>> +		drm_err(&ptdev->base,
>> +				"Performance counter sessions active when unplugging the driver!");
>> +
>> +	xa_destroy(&perf->sessions);
>> +
>> +	devm_kfree(ptdev->base.dev, ptdev->perf);
> 
> If we always call devm_kfree, then what is the point of allocating ptdev->perf
> with devm_kzalloc?

You're right, it's not necessary. The panthor_perf object could in
theory be allocated with devm, since the lifetime matches that of the
panthor_device, but it's simpler to drop the devm allocations.

> 
>> +	ptdev->perf = NULL;
>> +}
>> diff --git a/drivers/gpu/drm/panthor/panthor_perf.h b/drivers/gpu/drm/panthor/panthor_perf.h
>> index cff537a370c9..90af8b18358c 100644
>> --- a/drivers/gpu/drm/panthor/panthor_perf.h
>> +++ b/drivers/gpu/drm/panthor/panthor_perf.h
>> @@ -9,4 +9,7 @@ struct panthor_device;
>>   
>>   void panthor_perf_info_init(struct panthor_device *ptdev);
>>   
>> +int panthor_perf_init(struct panthor_device *ptdev);
>> +void panthor_perf_unplug(struct panthor_device *ptdev);
>> +
>>   #endif /* __PANTHOR_PERF_H__ */
>> -- 
>> 2.25.1
> 
> 
> Adrian Larumbe