Re: [DPU PATCH v3] drm/msm: Use atomic private_obj instead of subclassing

[Jeykumar Sankaran <jsanka-sgV2jX0FEOL9JmXXK+q4OQ@public.gmane.org>]

On 2018-03-20 04:01, Archit Taneja wrote:
> Hi,
> 
> On Tuesday 20 March 2018 01:28 AM, Sean Paul wrote:
>> Instead of subclassing atomic state, store driver private data in
>> private_obj/state. This allows us to remove the swap_state driver hook
>> for mdp5 and get closer to using the atomic helpers entirely.
>> 
>> Changes in v2:
>>   - Use state->state in disp duplicate_state callback (Jeykumar)
>> Changes in v3:
>>   - Update comment describing msm_kms_state (Jeykumar)
>> 
> 
> One difference w.r.t the patchset
> "drm/msm/mdp5: Use the new private_obj state" is that this
> adds the atomic private_obj for all kms backends, whereas the one
> I'd done originally just added it for mdp5, so this patch set
> is better in that respect.
> 
> The other difference is how we 'get' the private state. In this patch,
> the helper drm_atomic_get_private_obj_state() is used every time to
> get the private object state.
> 
> I'd tried to do the same initially, but I noticed that
> drm_atomic_get_private_obj_state() doesn't return the correct
> state post swapping of states. So, instead of relying on the helper,
> I created a helper called mdp5_get_existing_global_state() that
> returns the desired state(the state pointer in 
> msm_kms>state->base.state
> in this patch) in all funcs that are called post-swap.
> 
> 
> You could read about the issue on the the thread: "[RFC 1/3]
> drm/msm/mdp5: Add global state as a private atomic object"
> 
> The problem was quite apparent with db410c, where SMP blocks are
> assigned to planes. If the latest SMP state isn't referred when
> configuring SMP registers, we see underruns immediately.
> 
> An easy way to reproduce this is to use modset on db410c. I think
> it might occur with this patch too. It might be worth trying it
> out.
> 
> Thanks,
> Archit
> 
Hello Archit, Now that I am trying to use the private obj to maintain 
resource pool in DPU, I realize the need for retrieving existing / new 
state API's. Don't you think this support is missing in the DRM core 
fwk, considering how drm_atomic_get_existing_XXXX_state, 
drm_atomic_get_old_XXXX_state, drm_atomic_get_new_XXXX_state API's are 
available for CRTC/PLANE and CONNECTORS but not for private_obj's?

Thanks,
Jeykumar S.
>> Cc: Jeykumar Sankaran <jsanka@codeaurora.org>
>> Reviewed-by: Jeykumar Sankaran <jsanka@codeaurora.org>
>> Signed-off-by: Sean Paul <seanpaul@chromium.org>
>> ---
>>   drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c | 37 ++++++--------
>>   drivers/gpu/drm/msm/msm_atomic.c         | 30 -----------
>>   drivers/gpu/drm/msm/msm_drv.c            | 65 
>> ++++++++++++++++++++++--
>>   drivers/gpu/drm/msm/msm_drv.h            |  4 +-
>>   drivers/gpu/drm/msm/msm_kms.h            | 27 +++++-----
>>   5 files changed, 94 insertions(+), 69 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c 
>> b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
>> index 6d8e3a9a6fc0..f1a248419655 100644
>> --- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
>> +++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_kms.c
>> @@ -74,36 +74,32 @@ struct mdp5_state *mdp5_get_state(struct 
>> drm_atomic_state *s)
>>   {
>>   	struct msm_drm_private *priv = s->dev->dev_private;
>>   	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(priv->kms));
>> -	struct msm_kms_state *state = to_kms_state(s);
>> -	struct mdp5_state *new_state;
>> +	struct msm_kms_state *kms_state;
>>   	int ret;
>> 
>> -	if (state->state)
>> -		return state->state;
>> -
>>   	ret = drm_modeset_lock(&mdp5_kms->state_lock, s->acquire_ctx);
>>   	if (ret)
>>   		return ERR_PTR(ret);
>> 
>> -	new_state = kmalloc(sizeof(*mdp5_kms->state), GFP_KERNEL);
>> -	if (!new_state)
>> -		return ERR_PTR(-ENOMEM);
>> +	kms_state = msm_kms_get_state(s);
>> +	if (IS_ERR_OR_NULL(kms_state))
>> +		return (struct mdp5_state *)kms_state; /* casting ERR_PTR */
>> 
>> -	/* Copy state: */
>> -	new_state->hwpipe = mdp5_kms->state->hwpipe;
>> -	new_state->hwmixer = mdp5_kms->state->hwmixer;
>> -	if (mdp5_kms->smp)
>> -		new_state->smp = mdp5_kms->state->smp;
>> +	return kms_state->state;
>> +}
>> 
>> -	state->state = new_state;
>> +static void *mdp5_duplicate_state(void *state)
>> +{
>> +	if (!state)
>> +		return kzalloc(sizeof(struct mdp5_state), GFP_KERNEL);
>> 
>> -	return new_state;
>> +	return kmemdup(state, sizeof(struct mdp5_state), GFP_KERNEL);
>>   }
>> 
>> -static void mdp5_swap_state(struct msm_kms *kms, struct 
>> drm_atomic_state *state)
>> +static void mdp5_destroy_state(void *state)
>>   {
>> -	struct mdp5_kms *mdp5_kms = to_mdp5_kms(to_mdp_kms(kms));
>> -	swap(to_kms_state(state)->state, mdp5_kms->state);
>> +	struct mdp5_state *mdp_state = state;
>> +	kfree(mdp_state);
>>   }
>> 
>>   static void mdp5_prepare_commit(struct msm_kms *kms, struct 
>> drm_atomic_state *state)
>> @@ -229,7 +225,8 @@ static const struct mdp_kms_funcs kms_funcs = {
>>   		.irq             = mdp5_irq,
>>   		.enable_vblank   = mdp5_enable_vblank,
>>   		.disable_vblank  = mdp5_disable_vblank,
>> -		.swap_state      = mdp5_swap_state,
>> +		.duplicate_state = mdp5_duplicate_state,
>> +		.destroy_state	 = mdp5_destroy_state,
>>   		.prepare_commit  = mdp5_prepare_commit,
>>   		.complete_commit = mdp5_complete_commit,
>>   		.wait_for_crtc_commit_done = mdp5_wait_for_crtc_commit_done,
>> @@ -726,8 +723,6 @@ static void mdp5_destroy(struct platform_device 
>> *pdev)
>> 
>>   	if (mdp5_kms->rpm_enabled)
>>   		pm_runtime_disable(&pdev->dev);
>> -
>> -	kfree(mdp5_kms->state);
>>   }
>> 
>>   static int construct_pipes(struct mdp5_kms *mdp5_kms, int cnt,
>> diff --git a/drivers/gpu/drm/msm/msm_atomic.c 
>> b/drivers/gpu/drm/msm/msm_atomic.c
>> index 7e54eb65d096..1f53262ea46b 100644
>> --- a/drivers/gpu/drm/msm/msm_atomic.c
>> +++ b/drivers/gpu/drm/msm/msm_atomic.c
>> @@ -169,9 +169,6 @@ int msm_atomic_commit(struct drm_device *dev,
>>   	 */
>>   	BUG_ON(drm_atomic_helper_swap_state(state, false) < 0);
>> 
>> -	if (to_kms_state(state)->state)
>> -		priv->kms->funcs->swap_state(priv->kms, state);
>> -
>>   	/*
>>   	 * Provide the driver a chance to prepare for output fences. This 
>> is
>>   	 * done after the point of no return, but before asynchronous 
>> commits
>> @@ -210,30 +207,3 @@ int msm_atomic_commit(struct drm_device *dev,
>>   	drm_atomic_helper_cleanup_planes(dev, state);
>>   	return ret;
>>   }
>> -
>> -struct drm_atomic_state *msm_atomic_state_alloc(struct drm_device 
>> *dev)
>> -{
>> -	struct msm_kms_state *state = kzalloc(sizeof(*state), GFP_KERNEL);
>> -
>> -	if (!state || drm_atomic_state_init(dev, &state->base) < 0) {
>> -		kfree(state);
>> -		return NULL;
>> -	}
>> -
>> -	return &state->base;
>> -}
>> -
>> -void msm_atomic_state_clear(struct drm_atomic_state *s)
>> -{
>> -	struct msm_kms_state *state = to_kms_state(s);
>> -	drm_atomic_state_default_clear(&state->base);
>> -	kfree(state->state);
>> -	state->state = NULL;
>> -}
>> -
>> -void msm_atomic_state_free(struct drm_atomic_state *state)
>> -{
>> -	kfree(to_kms_state(state)->state);
>> -	drm_atomic_state_default_release(state);
>> -	kfree(state);
>> -}
>> diff --git a/drivers/gpu/drm/msm/msm_drv.c 
>> b/drivers/gpu/drm/msm/msm_drv.c
>> index 5219792e93bc..4c0740dc7854 100644
>> --- a/drivers/gpu/drm/msm/msm_drv.c
>> +++ b/drivers/gpu/drm/msm/msm_drv.c
>> @@ -121,9 +121,62 @@ static const struct drm_mode_config_funcs 
>> mode_config_funcs = {
>>   	.output_poll_changed = msm_fb_output_poll_changed,
>>   	.atomic_check = drm_atomic_helper_check,
>>   	.atomic_commit = msm_atomic_commit,
>> -	.atomic_state_alloc = msm_atomic_state_alloc,
>> -	.atomic_state_clear = msm_atomic_state_clear,
>> -	.atomic_state_free = msm_atomic_state_free,
>> +};
>> +
>> +static inline
>> +struct msm_kms *obj_to_kms(struct drm_private_obj *obj)
>> +{
>> +	return container_of(obj, struct msm_kms, base);
>> +}
>> +
>> +static inline
>> +struct msm_kms_state *state_to_kms_state(struct drm_private_state 
>> *state)
>> +{
>> +	return container_of(state, struct msm_kms_state, base);
>> +}
>> +
>> +struct msm_kms_state *msm_kms_get_state(struct drm_atomic_state *s)
>> +{
>> +	struct msm_drm_private *priv = s->dev->dev_private;
>> +	struct drm_private_obj *obj = &priv->kms->base;
>> +	struct drm_private_state *state;
>> +
>> +	state = drm_atomic_get_private_obj_state(s, obj);
>> +	if (IS_ERR_OR_NULL(state))
>> +		return (struct msm_kms_state *)state; /* casting ERR_PTR */
>> +
>> +	return state_to_kms_state(state);
>> +}
>> +
>> +static struct drm_private_state *
>> +msm_kms_duplicate_state(struct drm_private_obj *obj)
>> +{
>> +	struct msm_kms *kms = obj_to_kms(obj);
>> +	struct msm_kms_state *state = state_to_kms_state(obj->state);
>> +	struct msm_kms_state *new_state;
>> +
>> +	if (kms->funcs->duplicate_state)
>> +		new_state = kms->funcs->duplicate_state(state->state);
>> +
>> +	__drm_atomic_helper_private_obj_duplicate_state(obj, 
>> &new_state->base);
>> +
>> +	return &new_state->base;
>> +}
>> +
>> +static void msm_kms_destroy_state(struct drm_private_obj *obj,
>> +				  struct drm_private_state *state)
>> +{
>> +	struct msm_kms *kms = obj_to_kms(obj);
>> +	struct msm_kms_state *kms_state = state_to_kms_state(obj->state);
>> +
>> +	if (kms->funcs->destroy_state)
>> +		kms->funcs->destroy_state(kms_state->state);
>> +	kfree(kms_state);
>> +}
>> +
>> +static const struct drm_private_state_funcs kms_state_funcs = {
>> +	.atomic_duplicate_state = msm_kms_duplicate_state,
>> +	.atomic_destroy_state = msm_kms_destroy_state,
>>   };
>> 
>>   #ifdef CONFIG_DRM_MSM_REGISTER_LOGGING
>> @@ -341,6 +394,8 @@ static int msm_drm_uninit(struct device *dev)
>>   		}
>>   	}
>> 
>> +	drm_atomic_private_obj_fini(&kms->base);
>> +
>>   	msm_gem_shrinker_cleanup(ddev);
>> 
>>   	drm_kms_helper_poll_fini(ddev);
>> @@ -770,6 +825,10 @@ static int msm_drm_init(struct device *dev, 
>> struct drm_driver *drv)
>>   	}
>>   #endif
>> 
>> +	drm_atomic_private_obj_init(&kms->base,
>> +				    &kms->state.base,
>> +				    &kms_state_funcs);
>> +
>>   	/* perform subdriver post initialization */
>>   	if (kms && kms->funcs && kms->funcs->postinit) {
>>   		ret = kms->funcs->postinit(kms);
>> diff --git a/drivers/gpu/drm/msm/msm_drv.h 
>> b/drivers/gpu/drm/msm/msm_drv.h
>> index 292496b682e8..8cab333df717 100644
>> --- a/drivers/gpu/drm/msm/msm_drv.h
>> +++ b/drivers/gpu/drm/msm/msm_drv.h
>> @@ -598,9 +598,7 @@ struct msm_format {
>> 
>>   int msm_atomic_commit(struct drm_device *dev,
>>   		struct drm_atomic_state *state, bool nonblock);
>> -struct drm_atomic_state *msm_atomic_state_alloc(struct drm_device 
>> *dev);
>> -void msm_atomic_state_clear(struct drm_atomic_state *state);
>> -void msm_atomic_state_free(struct drm_atomic_state *state);
>> +struct msm_kms_state *msm_kms_get_state(struct drm_atomic_state 
>> *state);
>> 
>>   void msm_gem_unmap_vma(struct msm_gem_address_space *aspace,
>>   		struct msm_gem_vma *vma, struct sg_table *sgt);
>> diff --git a/drivers/gpu/drm/msm/msm_kms.h 
>> b/drivers/gpu/drm/msm/msm_kms.h
>> index 09ba1e79db50..5c1bcaf65fd9 100644
>> --- a/drivers/gpu/drm/msm/msm_kms.h
>> +++ b/drivers/gpu/drm/msm/msm_kms.h
>> @@ -57,6 +57,8 @@ struct msm_kms_funcs {
>>   	void (*disable_vblank)(struct msm_kms *kms, struct drm_crtc *crtc);
>>   	/* swap global atomic state: */
>>   	void (*swap_state)(struct msm_kms *kms, struct drm_atomic_state 
>> *state);
>> +	void *(*duplicate_state)(void *state);
>> +	void (*destroy_state)(void *state);
>>   	/* modeset, bracketing atomic_commit(): */
>>   	void (*prepare_fence)(struct msm_kms *kms,
>>   			struct drm_atomic_state *state);
>> @@ -114,7 +116,20 @@ struct msm_kms_funcs {
>>   #endif
>>   };
>> 
>> +/**
>> + * Subclass of drm_private_state, to allow kms backend to have driver
>> + * private global state.  The kms backend can do whatever it wants
>> + * with the ->state ptr.
>> + */
>> +struct msm_kms_state {
>> +	struct drm_private_state base;
>> +	void *state;
>> +};
>> +
>>   struct msm_kms {
>> +	struct drm_private_obj base;
>> +	struct msm_kms_state state;
>> +
>>   	const struct msm_kms_funcs *funcs;
>> 
>>   	/* irq number to be passed on to drm_irq_install */
>> @@ -124,18 +139,6 @@ struct msm_kms {
>>   	struct msm_gem_address_space *aspace;
>>   };
>> 
>> -/**
>> - * Subclass of drm_atomic_state, to allow kms backend to have driver
>> - * private global state.  The kms backend can do whatever it wants
>> - * with the ->state ptr.  On ->atomic_state_clear() the ->state ptr
>> - * is kfree'd and set back to NULL.
>> - */
>> -struct msm_kms_state {
>> -	struct drm_atomic_state base;
>> -	void *state;
>> -};
>> -#define to_kms_state(x) container_of(x, struct msm_kms_state, base)
>> -
>>   static inline void msm_kms_init(struct msm_kms *kms,
>>   		const struct msm_kms_funcs *funcs)
>>   {
>> 

-- 
Jeykumar S
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