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

[Noralf Trønnes]

Den 28.11.2022 13.10, skrev Thomas Zimmermann:
> 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.
> 

I prefer to drop this. When I see the subclassed plane state without any
additional state members I'm left wondering why this is done and I start
looking for a TODO.

Noralf.

> Best regards
> Thomas
> 
>>
>> Noralf.
>>
>>>
>>> Signed-off-by: Thomas Zimmermann <tzimmermann at 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 */
>