Re: [PATCH 1/9] drm/arcpgu: replace struct drm_simple_display_pipe with regular atomic helpers

On Mon Jul 6, 2026 at 4:01 PM CST, Thomas Zimmermann wrote:
> Hi
>
> Am 04.07.26 um 20:31 schrieb Ze Huang:
>> Instantiate plane, CRTC and encoder directly and wire them up with
>> standard atomic helpers.
>>
>> This removes arcpgu's dependency on deprecated simple-KMS display pipe
>> interface.
>>
>> Signed-off-by: Ze Huang <[email protected]>
>> ---
>>   drivers/gpu/drm/tiny/arcpgu.c | 165 +++++++++++++++++++++++++++++++++---------
>>   1 file changed, 131 insertions(+), 34 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/tiny/arcpgu.c b/drivers/gpu/drm/tiny/arcpgu.c
>> index c93d61ac0bb7..375cdb79e4e8 100644
>> --- a/drivers/gpu/drm/tiny/arcpgu.c
>> +++ b/drivers/gpu/drm/tiny/arcpgu.c
>> @@ -17,12 +17,12 @@
>>   #include <drm/drm_fbdev_dma.h>
>>   #include <drm/drm_fourcc.h>
>>   #include <drm/drm_framebuffer.h>
>> +#include <drm/drm_gem_atomic_helper.h>
>>   #include <drm/drm_gem_dma_helper.h>
>>   #include <drm/drm_gem_framebuffer_helper.h>
>>   #include <drm/drm_module.h>
>>   #include <drm/drm_of.h>
>>   #include <drm/drm_probe_helper.h>
>> -#include <drm/drm_simple_kms_helper.h>
>>   #include <linux/dma-mapping.h>
>>   #include <linux/module.h>
>>   #include <linux/of_reserved_mem.h>
>> @@ -52,14 +52,14 @@ struct arcpgu_drm_private {
>>   	struct drm_device	drm;
>>   	void __iomem		*regs;
>>   	struct clk		*clk;
>> -	struct drm_simple_display_pipe pipe;
>> +	struct drm_plane	plane;
>> +	struct drm_crtc		crtc;
>> +	struct drm_encoder	encoder;
>>   	struct drm_connector	sim_conn;
>>   };
>>   
>>   #define dev_to_arcpgu(x) container_of(x, struct arcpgu_drm_private, drm)
>>   
>> -#define pipe_to_arcpgu_priv(x) container_of(x, struct arcpgu_drm_private, pipe)
>> -
>>   static inline void arc_pgu_write(struct arcpgu_drm_private *arcpgu,
>>   				 unsigned int reg, u32 value)
>>   {
>> @@ -117,7 +117,7 @@ static const u32 arc_pgu_supported_formats[] = {
>>   
>>   static void arc_pgu_set_pxl_fmt(struct arcpgu_drm_private *arcpgu)
>>   {
>> -	const struct drm_framebuffer *fb = arcpgu->pipe.plane.state->fb;
>> +	const struct drm_framebuffer *fb = arcpgu->plane.state->fb;
>>   	uint32_t pixel_format = fb->format->format;
>>   	u32 format = DRM_FORMAT_INVALID;
>>   	int i;
>> @@ -139,10 +139,10 @@ static void arc_pgu_set_pxl_fmt(struct arcpgu_drm_private *arcpgu)
>>   	arc_pgu_write(arcpgu, ARCPGU_REG_CTRL, reg_ctrl);
>>   }
>>   
>> -static enum drm_mode_status arc_pgu_mode_valid(struct drm_simple_display_pipe *pipe,
>> -					       const struct drm_display_mode *mode)
>> +static enum drm_mode_status arcpgu_crtc_helper_mode_valid(struct drm_crtc *crtc,
>> +							  const struct drm_display_mode *mode)
>>   {
>> -	struct arcpgu_drm_private *arcpgu = pipe_to_arcpgu_priv(pipe);
>> +	struct arcpgu_drm_private *arcpgu = dev_to_arcpgu(crtc->dev);
>>   	long rate, clk_rate = mode->clock * 1000;
>>   	long diff = clk_rate / 200; /* +-0.5% allowed by HDMI spec */
>>   
>> @@ -155,7 +155,7 @@ static enum drm_mode_status arc_pgu_mode_valid(struct drm_simple_display_pipe *p
>>   
>>   static void arc_pgu_mode_set(struct arcpgu_drm_private *arcpgu)
>>   {
>> -	struct drm_display_mode *m = &arcpgu->pipe.crtc.state->adjusted_mode;
>> +	struct drm_display_mode *m = &arcpgu->crtc.state->adjusted_mode;
>>   	u32 val;
>>   
>>   	arc_pgu_write(arcpgu, ARCPGU_REG_FMT,
>> @@ -194,11 +194,10 @@ static void arc_pgu_mode_set(struct arcpgu_drm_private *arcpgu)
>>   	clk_set_rate(arcpgu->clk, m->crtc_clock * 1000);
>>   }
>>   
>> -static void arc_pgu_enable(struct drm_simple_display_pipe *pipe,
>> -			   struct drm_crtc_state *crtc_state,
>> -			   struct drm_plane_state *plane_state)
>> +static void arcpgu_crtc_helper_atomic_enable(struct drm_crtc *crtc,
>> +					     struct drm_atomic_commit *state)
>
> Since you're adding these functions anew, please use 'commit' for the 
> name of the drm_atomic_commit.  Here and everywhere else in the series.  
> You don't have to update existing functions, of course.
>
> The name 'state' is a bit off here and comes from when drm_atomic_commit 
> was still called drm_atomic_state.
>
> CRTCs, plane, etc have state, but the update of these states is called 
> commit.
>

Thanks for your explanation.

I will change to name 'commit' for type drm_atomic_commit, here and
everywhere else in the series.

>
>>   {
>> -	struct arcpgu_drm_private *arcpgu = pipe_to_arcpgu_priv(pipe);
>> +	struct arcpgu_drm_private *arcpgu = dev_to_arcpgu(crtc->dev);
>>   
>>   	arc_pgu_mode_set(arcpgu);
>>   
>> @@ -208,9 +207,10 @@ static void arc_pgu_enable(struct drm_simple_display_pipe *pipe,
>>   		      ARCPGU_CTRL_ENABLE_MASK);
>>   }
>>   
>> -static void arc_pgu_disable(struct drm_simple_display_pipe *pipe)
>> +static void arcpgu_crtc_helper_atomic_disable(struct drm_crtc *crtc,
>> +					      struct drm_atomic_commit *state)
>>   {
>> -	struct arcpgu_drm_private *arcpgu = pipe_to_arcpgu_priv(pipe);
>> +	struct arcpgu_drm_private *arcpgu = dev_to_arcpgu(crtc->dev);
>>   
>>   	clk_disable_unprepare(arcpgu->clk);
>>   	arc_pgu_write(arcpgu, ARCPGU_REG_CTRL,
>> @@ -218,35 +218,106 @@ static void arc_pgu_disable(struct drm_simple_display_pipe *pipe)
>>   			      ~ARCPGU_CTRL_ENABLE_MASK);
>>   }
>>   
>> -static void arc_pgu_update(struct drm_simple_display_pipe *pipe,
>> -			   struct drm_plane_state *state)
>> +static void arcpgu_plane_helper_atomic_update(struct drm_plane *plane,
>> +					      struct drm_atomic_commit *state)
>>   {
>>   	struct arcpgu_drm_private *arcpgu;
>>   	struct drm_gem_dma_object *gem;
>>   
>> -	if (!pipe->plane.state->fb)
>> +	if (!plane->state->fb)
>>   		return;
>>   
>> -	arcpgu = pipe_to_arcpgu_priv(pipe);
>> -	gem = drm_fb_dma_get_gem_obj(pipe->plane.state->fb, 0);
>> +	arcpgu = dev_to_arcpgu(plane->dev);
>> +	gem = drm_fb_dma_get_gem_obj(plane->state->fb, 0);
>>   	arc_pgu_write(arcpgu, ARCPGU_REG_BUF0_ADDR, gem->dma_addr);
>>   }
>>   
>> -static const struct drm_simple_display_pipe_funcs arc_pgu_pipe_funcs = {
>> -	.update = arc_pgu_update,
>> -	.mode_valid = arc_pgu_mode_valid,
>> -	.enable	= arc_pgu_enable,
>> -	.disable = arc_pgu_disable,
>> -};
>> -
>>   static const struct drm_mode_config_funcs arcpgu_drm_modecfg_funcs = {
>> -	.fb_create  = drm_gem_fb_create,
>> +	.fb_create = drm_gem_fb_create,
>>   	.atomic_check = drm_atomic_helper_check,
>>   	.atomic_commit = drm_atomic_helper_commit,
>>   };
>>   
>>   DEFINE_DRM_GEM_DMA_FOPS(arcpgu_drm_ops);
>>   
>> +static int arcpgu_plane_helper_atomic_check(struct drm_plane *plane,
>> +					    struct drm_atomic_commit *state)
>> +{
>> +	struct drm_plane_state *plane_state = drm_atomic_get_new_plane_state(state, plane);
>> +	struct drm_crtc *crtc = plane_state->crtc;
>> +	struct drm_crtc_state *crtc_state = NULL;
>> +	int ret;
>> +
>> +	if (crtc)
>> +		crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
>> +
>> +	ret = drm_atomic_helper_check_plane_state(plane_state, crtc_state,
>> +						  DRM_PLANE_NO_SCALING,
>> +						  DRM_PLANE_NO_SCALING,
>> +						  false, false);
>> +	return ret;
>
>
> Return directly here.
>

OK

>
>> +}
>> +
>> +static const struct drm_plane_helper_funcs arcpgu_plane_helper_funcs = {
>> +	.prepare_fb	= drm_gem_plane_helper_prepare_fb,
>> +	.atomic_check	= arcpgu_plane_helper_atomic_check,
>> +	.atomic_update	= arcpgu_plane_helper_atomic_update,
>> +};
>> +
>> +static bool arcpgu_plane_format_mod_supported(struct drm_plane *plane,
>> +					      u32 format,
>> +					      u64 modifier)
>> +{
>> +	return modifier == DRM_FORMAT_MOD_LINEAR;
>> +}
>
> Please remove this function. It doesn't really do anything besides DRM's 
> standard behavior.
>


Will do

>> +
>> +static const struct drm_plane_funcs arcpgu_plane_funcs = {
>> +	.update_plane		= drm_atomic_helper_update_plane,
>> +	.disable_plane		= drm_atomic_helper_disable_plane,
>> +	.destroy		= drm_plane_cleanup,
>> +	.reset			= drm_atomic_helper_plane_reset,
>> +	.atomic_duplicate_state	= drm_atomic_helper_plane_duplicate_state,
>> +	.atomic_destroy_state	= drm_atomic_helper_plane_destroy_state,
>> +	.format_mod_supported	= arcpgu_plane_format_mod_supported,
>> +};
>> +
>> +static int arcpgu_crtc_helper_atomic_check(struct drm_crtc *crtc,
>> +					   struct drm_atomic_commit *state)
>> +{
>> +	struct drm_crtc_state *crtc_state = drm_atomic_get_new_crtc_state(state, crtc);
>> +	int ret;
>> +
>> +	if (!crtc_state->enable)
>> +		goto out;
>> +
>> +	ret = drm_atomic_helper_check_crtc_primary_plane(crtc_state);
>> +	if (ret)
>> +		return ret;
>> +
>> +out:
>> +	return drm_atomic_add_affected_planes(state, crtc);
>
> Instead of using out, I'd rather use
>
>    if (crtc->enable) {
>        //do checks
>    }
>
>    return add_affected planes.
>
> Seems more natural to me.
>

Will do

>> +}
>> +
>> +static const struct drm_crtc_helper_funcs arcpgu_crtc_helper_funcs = {
>> +	.mode_valid	= arcpgu_crtc_helper_mode_valid,
>> +	.atomic_check	= arcpgu_crtc_helper_atomic_check,
>> +	.atomic_enable	= arcpgu_crtc_helper_atomic_enable,
>> +	.atomic_disable	= arcpgu_crtc_helper_atomic_disable,
>> +};
>> +
>> +static const struct drm_crtc_funcs arcpgu_crtc_funcs = {
>> +	.reset			= drm_atomic_helper_crtc_reset,
>> +	.destroy		= drm_crtc_cleanup,
>> +	.set_config		= drm_atomic_helper_set_config,
>> +	.page_flip		= drm_atomic_helper_page_flip,
>> +	.atomic_duplicate_state	= drm_atomic_helper_crtc_duplicate_state,
>> +	.atomic_destroy_state	= drm_atomic_helper_crtc_destroy_state,
>> +};
>> +
>> +static const struct drm_encoder_funcs arcpgu_encoder_funcs = {
>> +	.destroy = drm_encoder_cleanup,
>> +};
>> +
>>   static int arcpgu_load(struct arcpgu_drm_private *arcpgu)
>>   {
>>   	struct platform_device *pdev = to_platform_device(arcpgu->drm.dev);
>> @@ -254,6 +325,9 @@ static int arcpgu_load(struct arcpgu_drm_private *arcpgu)
>>   	struct device_node *endpoint_node = NULL;
>>   	struct drm_connector *connector = NULL;
>>   	struct drm_device *drm = &arcpgu->drm;
>> +	struct drm_plane *plane;
>> +	struct drm_encoder *encoder;
>> +	struct drm_crtc *crtc;
>>   	int ret;
>>   
>>   	arcpgu->clk = devm_clk_get(drm->dev, "pxlclk");
>> @@ -301,12 +375,35 @@ static int arcpgu_load(struct arcpgu_drm_private *arcpgu)
>>   			return ret;
>>   	}
>>   
>> -	ret = drm_simple_display_pipe_init(drm, &arcpgu->pipe, &arc_pgu_pipe_funcs,
>> -					   arc_pgu_supported_formats,
>> -					   ARRAY_SIZE(arc_pgu_supported_formats),
>> -					   NULL, connector);
>> +	plane = &arcpgu->plane;
>> +	ret = drm_universal_plane_init(drm, plane, 0,
>> +				       &arcpgu_plane_funcs,
>> +				       arc_pgu_supported_formats,
>> +				       ARRAY_SIZE(arc_pgu_supported_formats),
>> +				       NULL,
>> +				       DRM_PLANE_TYPE_PRIMARY, NULL);
>>   	if (ret)
>>   		return ret;
>> +	drm_plane_helper_add(plane, &arcpgu_plane_helper_funcs);
>> +
>> +	crtc = &arcpgu->crtc;
>> +	ret = drm_crtc_init_with_planes(drm, crtc, plane, NULL,
>> +					&arcpgu_crtc_funcs, NULL);
>> +	if (ret)
>> +		return ret;
>> +	drm_crtc_helper_add(crtc, &arcpgu_crtc_helper_funcs);
>> +
>> +	encoder = &arcpgu->encoder;
>> +	ret = drm_encoder_init(drm, encoder, &arcpgu_encoder_funcs, DRM_MODE_ENCODER_NONE, NULL);
>> +	if (ret)
>> +		return ret;
>> +	encoder->possible_crtcs = drm_crtc_mask(crtc);
>
>
> I think plane, CRTC, and encoder should go before testing the 
> encoder_node at [1].
>
> Then comes the encoder_node test.  If true, do a single encoder-node 
> branch,  or else to a single connector-based branch.   That would 
> simplify the overall logic in this helper.
>
> [1] 
> https://elixir.bootlin.com/linux/v7.1.2/source/drivers/gpu/drm/tiny/arcpgu.c#L287
>

OK, will move them before the encoder_node test

>
>> +
>> +	if (connector) {
>> +		ret = drm_connector_attach_encoder(connector, encoder);
>> +		if (ret)
>> +			return ret;
>> +	}
>>   
>>   	if (encoder_node) {
>>   		/* Locate drm bridge from the hdmi encoder DT node */
>> @@ -315,7 +412,7 @@ static int arcpgu_load(struct arcpgu_drm_private *arcpgu)
>>   		if (!bridge)
>>   			return -EPROBE_DEFER;
>>   
>> -		ret = drm_simple_display_pipe_attach_bridge(&arcpgu->pipe, bridge);
>> +		ret = drm_bridge_attach(encoder, bridge, NULL, 0);
>>   		if (ret)
>>   			return ret;
>>   	}
>> @@ -342,7 +439,7 @@ static int arcpgu_show_pxlclock(struct seq_file *m, void *arg)
>>   	struct drm_device *drm = node->minor->dev;
>>   	struct arcpgu_drm_private *arcpgu = dev_to_arcpgu(drm);
>>   	unsigned long clkrate = clk_get_rate(arcpgu->clk);
>> -	unsigned long mode_clock = arcpgu->pipe.crtc.mode.crtc_clock * 1000;
>> +	unsigned long mode_clock = arcpgu->crtc.mode.crtc_clock * 1000;
>
> Here, mode is an obsolete field. The correct field is crtc->state->mode.

Will correct the field

>
> Best regards
> Thomas
>
>>   
>>   	seq_printf(m, "hw  : %lu\n", clkrate);
>>   	seq_printf(m, "mode: %lu\n", mode_clock);
>>

Thanks,
Ze