Re: [PATCH 6/8] drm/mipi-dbi: Support shadow-plane state

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 25.11.22 um 18:48 schrieb Noralf Trønnes:
> 
> 
> Den 21.11.2022 11.45, skrev Thomas Zimmermann:
>> Introduce struct drm_mipi_dbi_plane_state that contains state related to
>> MIPI DBI. It currently only inherits from struct drm_shadow_plane_state,
>> so that MIPI DBI drivers can use the vmap'ed GEM-buffer memory. Implement
>> state helpers, the {begin,end}_fb_access helpers and wire up everything.
>>
>> With this commit, MIPI DBI drivers can access the GEM object's memory
>> that is provided by shadow-plane state. The actual changes to drivers
>> are implemented separately. The new struct drm_mipi_dbi_plane was added
>> to avoid exposing struct drm_shadow_plane_state directly. The latter is
>> a detail of the actual implementation and having it in the MIPI driver
>> interface seems unintuitive.
> 
> I don't understand this reasoning. The update functions still uses
> drm_shadow_plane_state in order to access ->data[0]. If you want to
> avoid exposing it, can't you add an accessor function for ->data[0]
> instead? That would actually be useful to me at least since when I first
> read the shadow plane code I didn't understand what data really was
> referring to. fb_map would have been more clear to me.

There's nothing wrong with accessing shadow-plane state directly. I 
simply found it non-intuitive to leave MIPI without it's own plane-state 
structure.  From the perspective of a MIPI-based driver, up-casting to a 
shadow-plane state feels arbitrary. Upcasting to a MIPI plane state 
appears logical.

Anyway, if using the shadow-plane state without the mipi plane state is 
preferred, I'll change the code accordingly.

Best regards
Thomas

> 
> Noralf.
> 
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>>   drivers/gpu/drm/drm_mipi_dbi.c | 113 +++++++++++++++++++++++++++++++++
>>   drivers/gpu/drm/tiny/ili9225.c |   5 ++
>>   drivers/gpu/drm/tiny/st7586.c  |   5 ++
>>   include/drm/drm_mipi_dbi.h     |  30 ++++++++-
>>   4 files changed, 152 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c
>> index 40e59a3a6481e..3030344d25b48 100644
>> --- a/drivers/gpu/drm/drm_mipi_dbi.c
>> +++ b/drivers/gpu/drm/drm_mipi_dbi.c
>> @@ -436,6 +436,119 @@ void mipi_dbi_pipe_disable(struct drm_simple_display_pipe *pipe)
>>   }
>>   EXPORT_SYMBOL(mipi_dbi_pipe_disable);
>>   
>> +/**
>> + * mipi_dbi_pipe_begin_fb_access - MIPI DBI pipe begin-access helper
>> + * @pipe: Display pipe
>> + * @plane_state: Plane state
>> + *
>> + * This function implements struct &drm_simple_display_funcs.begin_fb_access.
>> + *
>> + * See drm_gem_begin_shadow_fb_access() for details and mipi_dbi_pipe_cleanup_fb()
>> + * for cleanup.
>> + *
>> + * Returns:
>> + * 0 on success, or a negative errno code otherwise.
>> + */
>> +int mipi_dbi_pipe_begin_fb_access(struct drm_simple_display_pipe *pipe,
>> +				  struct drm_plane_state *plane_state)
>> +{
>> +	return drm_gem_begin_shadow_fb_access(&pipe->plane, plane_state);
>> +}
>> +EXPORT_SYMBOL(mipi_dbi_pipe_begin_fb_access);
>> +
>> +/**
>> + * mipi_dbi_pipe_end_fb_access - MIPI DBI pipe end-access helper
>> + * @pipe: Display pipe
>> + * @plane_state: Plane state
>> + *
>> + * This function implements struct &drm_simple_display_funcs.end_fb_access.
>> + *
>> + * See mipi_dbi_pipe_begin_fb_access().
>> + */
>> +void mipi_dbi_pipe_end_fb_access(struct drm_simple_display_pipe *pipe,
>> +				 struct drm_plane_state *plane_state)
>> +{
>> +	drm_gem_end_shadow_fb_access(&pipe->plane, plane_state);
>> +}
>> +EXPORT_SYMBOL(mipi_dbi_pipe_end_fb_access);
>> +
>> +/**
>> + * mipi_dbi_pipe_reset_plane - MIPI DBI plane-reset helper
>> + * @pipe: Display pipe
>> + *
>> + * This function implements struct &drm_simple_display_funcs.reset_plane
>> + * for MIPI DBI planes.
>> + */
>> +void mipi_dbi_pipe_reset_plane(struct drm_simple_display_pipe *pipe)
>> +{
>> +	struct drm_plane *plane = &pipe->plane;
>> +	struct mipi_dbi_plane_state *mipi_dbi_plane_state;
>> +
>> +	if (plane->state) {
>> +		mipi_dbi_pipe_destroy_plane_state(pipe, plane->state);
>> +		plane->state = NULL; /* must be set to NULL here */
>> +	}
>> +
>> +	mipi_dbi_plane_state = kzalloc(sizeof(*mipi_dbi_plane_state), GFP_KERNEL);
>> +	if (!mipi_dbi_plane_state)
>> +		return;
>> +	__drm_gem_reset_shadow_plane(plane, &mipi_dbi_plane_state->shadow_plane_state);
>> +}
>> +EXPORT_SYMBOL(mipi_dbi_pipe_reset_plane);
>> +
>> +/**
>> + * mipi_dbi_pipe_duplicate_plane_state - duplicates MIPI DBI plane state
>> + * @pipe: Display pipe
>> + *
>> + * This function implements struct &drm_simple_display_funcs.duplicate_plane_state
>> + * for MIPI DBI planes.
>> + *
>> + * See drm_gem_duplicate_shadow_plane_state() for additional details.
>> + *
>> + * Returns:
>> + * A pointer to a new plane state on success, or NULL otherwise.
>> + */
>> +struct drm_plane_state *mipi_dbi_pipe_duplicate_plane_state(struct drm_simple_display_pipe *pipe)
>> +{
>> +	struct drm_plane *plane = &pipe->plane;
>> +	struct drm_plane_state *plane_state = plane->state;
>> +	struct mipi_dbi_plane_state *new_mipi_dbi_plane_state;
>> +	struct drm_shadow_plane_state *new_shadow_plane_state;
>> +
>> +	if (!plane_state)
>> +		return NULL;
>> +
>> +	new_mipi_dbi_plane_state = kzalloc(sizeof(*new_mipi_dbi_plane_state), GFP_KERNEL);
>> +	if (!new_mipi_dbi_plane_state)
>> +		return NULL;
>> +	new_shadow_plane_state = &new_mipi_dbi_plane_state->shadow_plane_state;
>> +
>> +	__drm_gem_duplicate_shadow_plane_state(plane, new_shadow_plane_state);
>> +
>> +	return &new_shadow_plane_state->base;
>> +}
>> +EXPORT_SYMBOL(mipi_dbi_pipe_duplicate_plane_state);
>> +
>> +/**
>> + * mipi_dbi_pipe_destroy_plane_state - cleans up MIPI DBI plane state
>> + * @pipe: Display pipe
>> + * @plane_state: Plane state
>> + *
>> + * This function implements struct drm_simple_display_funcs.destroy_plane_state
>> + * for MIPI DBI planes.
>> + *
>> + * See drm_gem_destroy_shadow_plane_state() for additional details.
>> + */
>> +void mipi_dbi_pipe_destroy_plane_state(struct drm_simple_display_pipe *pipe,
>> +				       struct drm_plane_state *plane_state)
>> +{
>> +	struct mipi_dbi_plane_state *mipi_dbi_plane_state = to_mipi_dbi_plane_state(plane_state);
>> +
>> +	__drm_gem_destroy_shadow_plane_state(&mipi_dbi_plane_state->shadow_plane_state);
>> +	kfree(mipi_dbi_plane_state);
>> +}
>> +EXPORT_SYMBOL(mipi_dbi_pipe_destroy_plane_state);
>> +
>>   static int mipi_dbi_connector_get_modes(struct drm_connector *connector)
>>   {
>>   	struct mipi_dbi_dev *dbidev = drm_to_mipi_dbi_dev(connector->dev);
>> diff --git a/drivers/gpu/drm/tiny/ili9225.c b/drivers/gpu/drm/tiny/ili9225.c
>> index 0115c4090f9e7..9e55ce28b4552 100644
>> --- a/drivers/gpu/drm/tiny/ili9225.c
>> +++ b/drivers/gpu/drm/tiny/ili9225.c
>> @@ -349,6 +349,11 @@ static const struct drm_simple_display_pipe_funcs ili9225_pipe_funcs = {
>>   	.enable		= ili9225_pipe_enable,
>>   	.disable	= ili9225_pipe_disable,
>>   	.update		= ili9225_pipe_update,
>> +	.begin_fb_access = mipi_dbi_pipe_begin_fb_access,
>> +	.end_fb_access	= mipi_dbi_pipe_end_fb_access,
>> +	.reset_plane	= mipi_dbi_pipe_reset_plane,
>> +	.duplicate_plane_state = mipi_dbi_pipe_duplicate_plane_state,
>> +	.destroy_plane_state = mipi_dbi_pipe_destroy_plane_state,
>>   };
>>   
>>   static const struct drm_display_mode ili9225_mode = {
>> diff --git a/drivers/gpu/drm/tiny/st7586.c b/drivers/gpu/drm/tiny/st7586.c
>> index e773b1f2fd5f3..76b13cefc904f 100644
>> --- a/drivers/gpu/drm/tiny/st7586.c
>> +++ b/drivers/gpu/drm/tiny/st7586.c
>> @@ -277,6 +277,11 @@ static const struct drm_simple_display_pipe_funcs st7586_pipe_funcs = {
>>   	.enable		= st7586_pipe_enable,
>>   	.disable	= st7586_pipe_disable,
>>   	.update		= st7586_pipe_update,
>> +	.begin_fb_access = mipi_dbi_pipe_begin_fb_access,
>> +	.end_fb_access	= mipi_dbi_pipe_end_fb_access,
>> +	.reset_plane	= mipi_dbi_pipe_reset_plane,
>> +	.duplicate_plane_state = mipi_dbi_pipe_duplicate_plane_state,
>> +	.destroy_plane_state = mipi_dbi_pipe_destroy_plane_state,
>>   };
>>   
>>   static const struct drm_display_mode st7586_mode = {
>> diff --git a/include/drm/drm_mipi_dbi.h b/include/drm/drm_mipi_dbi.h
>> index 36ac8495566b0..0213d4aae0326 100644
>> --- a/include/drm/drm_mipi_dbi.h
>> +++ b/include/drm/drm_mipi_dbi.h
>> @@ -10,6 +10,7 @@
>>   
>>   #include <linux/mutex.h>
>>   #include <drm/drm_device.h>
>> +#include <drm/drm_gem_atomic_helper.h>
>>   #include <drm/drm_simple_kms_helper.h>
>>   
>>   struct drm_rect;
>> @@ -18,6 +19,19 @@ struct iosys_map;
>>   struct regulator;
>>   struct spi_device;
>>   
>> +/**
>> + * struct mipi_dbi_plane_state - MIPI DBI plane state
>> + */
>> +struct mipi_dbi_plane_state {
>> +	struct drm_shadow_plane_state shadow_plane_state;
>> +};
>> +
>> +static inline struct mipi_dbi_plane_state *
>> +to_mipi_dbi_plane_state(struct drm_plane_state *plane_state)
>> +{
>> +	return container_of(plane_state, struct mipi_dbi_plane_state, shadow_plane_state.base);
>> +}
>> +
>>   /**
>>    * struct mipi_dbi - MIPI DBI interface
>>    */
>> @@ -164,6 +178,15 @@ void mipi_dbi_enable_flush(struct mipi_dbi_dev *dbidev,
>>   			   struct drm_crtc_state *crtc_state,
>>   			   struct drm_plane_state *plan_state);
>>   void mipi_dbi_pipe_disable(struct drm_simple_display_pipe *pipe);
>> +int mipi_dbi_pipe_begin_fb_access(struct drm_simple_display_pipe *pipe,
>> +				  struct drm_plane_state *plane_state);
>> +void mipi_dbi_pipe_end_fb_access(struct drm_simple_display_pipe *pipe,
>> +				 struct drm_plane_state *plane_state);
>> +void mipi_dbi_pipe_reset_plane(struct drm_simple_display_pipe *pipe);
>> +struct drm_plane_state *mipi_dbi_pipe_duplicate_plane_state(struct drm_simple_display_pipe *pipe);
>> +void mipi_dbi_pipe_destroy_plane_state(struct drm_simple_display_pipe *pipe,
>> +				       struct drm_plane_state *plane_state);
>> +
>>   void mipi_dbi_hw_reset(struct mipi_dbi *dbi);
>>   bool mipi_dbi_display_is_on(struct mipi_dbi *dbi);
>>   int mipi_dbi_poweron_reset(struct mipi_dbi_dev *dbidev);
>> @@ -223,6 +246,11 @@ static inline void mipi_dbi_debugfs_init(struct drm_minor *minor) {}
>>   	.mode_valid = mipi_dbi_pipe_mode_valid, \
>>   	.enable = (enable_), \
>>   	.disable = mipi_dbi_pipe_disable, \
>> -	.update = mipi_dbi_pipe_update
>> +	.update = mipi_dbi_pipe_update, \
>> +	.begin_fb_access = mipi_dbi_pipe_begin_fb_access, \
>> +	.end_fb_access = mipi_dbi_pipe_end_fb_access, \
>> +	.reset_plane = mipi_dbi_pipe_reset_plane, \
>> +	.duplicate_plane_state = mipi_dbi_pipe_duplicate_plane_state, \
>> +	.destroy_plane_state = mipi_dbi_pipe_destroy_plane_state
>>   
>>   #endif /* __LINUX_MIPI_DBI_H */

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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