Re: [PATCHv3/RFC 1/4] drm/arm: Factor out generic afbc helpers

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Nov 21, 2019 at 06:22:44PM +0100, Andrzej Pietrasiewicz wrote:
> These are useful for other users of afbc, e.g. rockchip.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
>  drivers/gpu/drm/Makefile          |  2 +-
>  drivers/gpu/drm/drm_afbc.c        | 84 +++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_fourcc.c      | 11 +++-
>  drivers/gpu/drm/drm_framebuffer.c | 71 +++++++++++++++++++++++++-
>  include/drm/drm_afbc.h            | 35 +++++++++++++
>  5 files changed, 199 insertions(+), 4 deletions(-)
>  create mode 100644 drivers/gpu/drm/drm_afbc.c
>  create mode 100644 include/drm/drm_afbc.h
> 
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index d9bcc9f2a0a4..3a58f30b83a6 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -44,7 +44,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_dsc.o drm_probe_helper
>  		drm_simple_kms_helper.o drm_modeset_helper.o \
>  		drm_scdc_helper.o drm_gem_framebuffer_helper.o \
>  		drm_atomic_state_helper.o drm_damage_helper.o \
> -		drm_format_helper.o drm_self_refresh_helper.o
> +		drm_format_helper.o drm_self_refresh_helper.o drm_afbc.o

Just a quick drive-by:
- you can't put this into helpers and call from core code. This should be
  core code. Also, I'd have just stuffed it into drm_format.c.

- If you want to keep your separate file, please include it in the doc
  template, next to the format handling functions.
>  
>  drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
>  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
> diff --git a/drivers/gpu/drm/drm_afbc.c b/drivers/gpu/drm/drm_afbc.c
> new file mode 100644
> index 000000000000..f308c4719546
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_afbc.c
> @@ -0,0 +1,84 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * (C) 2019 Collabora Ltd.
> + *
> + * author: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> + *
> + */
> +#include <linux/module.h>
> +
> +#include <drm/drm_afbc.h>
> +#include <drm/drm_device.h>
> +#include <drm/drm_fourcc.h>
> +#include <drm/drm_gem.h>
> +#include <drm/drm_mode.h>
> +#include <drm/drm_print.h>
> +
> +/**
> + * drm_afbc_get_superblk_wh - extract afbc block width/height from modifier
> + * @modifier: the modifier to be looked at
> + * @w: address of a place to store the block width
> + * @h: address of a place to store the block height
> + *
> + * Returns: true if the modifier describes a supported block size
> + */
> +bool drm_afbc_get_superblk_wh(u64 modifier, u32 *w, u32 *h)
> +{
> +	switch (modifier & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK) {
> +	case AFBC_FORMAT_MOD_BLOCK_SIZE_16x16:
> +		*w = 16;
> +		*h = 16;
> +		break;
> +	case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8:
> +		*w = 32;
> +		*h = 8;
> +		break;
> +	case AFBC_FORMAT_MOD_BLOCK_SIZE_64x4:
> +		/* fall through */
> +	case AFBC_FORMAT_MOD_BLOCK_SIZE_32x8_64x4:
> +		/* fall through */
> +	default:
> +		DRM_DEBUG_KMS("Invalid AFBC_FORMAT_MOD_BLOCK_SIZE: %lld.\n",
> +			      modifier & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK);
> +		return false;
> +	}
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(drm_afbc_get_superblk_wh);
> +
> +/**
> + * drm_afbc_get_parameters - extract afbc parameters from mode command
> + * @mode_cmd: mode command to be looked at
> + * @afbc: address of a struct to be filled in
> + */
> +void drm_afbc_get_parameters(const struct drm_mode_fb_cmd2 *mode_cmd,
> +			     struct drm_afbc *afbc)
> +{
> +	drm_afbc_get_superblk_wh(mode_cmd->modifier[0],
> +				 &afbc->tile_w, &afbc->tile_h);
> +	afbc->width = mode_cmd->pitches[0];
> +	afbc->height =
> +		DIV_ROUND_UP(mode_cmd->height, afbc->tile_h) * afbc->tile_h;
> +	afbc->offset = mode_cmd->offsets[0];
> +}
> +EXPORT_SYMBOL(drm_afbc_get_parameters);
> +
> +/**
> + * drm_is_afbc - test if the modifier describes an afbc buffer
> + * @modifier - modifier to be tested
> + *
> + * Returns: true if the modifier describes an afbc buffer
> + */
> +bool drm_is_afbc(u64 modifier)
> +{
> +	/* is it ARM AFBC? */
> +	if ((modifier & DRM_FORMAT_MOD_ARM_AFBC(0)) == 0)
> +		return false;
> +
> +	/* Block size must be known */
> +	if ((modifier & AFBC_FORMAT_MOD_BLOCK_SIZE_MASK) == 0)
> +		return false;
> +
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(drm_is_afbc);
> diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
> index c630064ccf41..8d9f197cc0ab 100644
> --- a/drivers/gpu/drm/drm_fourcc.c
> +++ b/drivers/gpu/drm/drm_fourcc.c
> @@ -27,6 +27,7 @@
>  #include <linux/export.h>
>  #include <linux/kernel.h>
>  
> +#include <drm/drm_afbc.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_fourcc.h>
>  
> @@ -322,8 +323,14 @@ drm_get_format_info(struct drm_device *dev,
>  {
>  	const struct drm_format_info *info = NULL;
>  
> -	if (dev->mode_config.funcs->get_format_info)
> -		info = dev->mode_config.funcs->get_format_info(mode_cmd);
> +	/* bypass driver callback if afbc */
> +	if (!drm_is_afbc(mode_cmd->modifier[0]))
> +		if (dev->mode_config.funcs->get_format_info) {
> +			const struct drm_mode_config_funcs *funcs;
> +
> +			funcs = dev->mode_config.funcs;
> +			info = funcs->get_format_info(mode_cmd);
> +		}
>  
>  	if (!info)
>  		info = drm_format_info(mode_cmd->pixel_format);
> diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
> index 57564318ceea..303eea624a02 100644
> --- a/drivers/gpu/drm/drm_framebuffer.c
> +++ b/drivers/gpu/drm/drm_framebuffer.c
> @@ -23,6 +23,7 @@
>  #include <linux/export.h>
>  #include <linux/uaccess.h>
>  
> +#include <drm/drm_afbc.h>
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_uapi.h>
>  #include <drm/drm_auth.h>
> @@ -31,6 +32,7 @@
>  #include <drm/drm_file.h>
>  #include <drm/drm_fourcc.h>
>  #include <drm/drm_framebuffer.h>
> +#include <drm/drm_gem.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_util.h>
>  
> @@ -168,7 +170,69 @@ static int fb_plane_height(int height,
>  	return DIV_ROUND_UP(height, format->vsub);
>  }
>  
> +static int afbc_check(struct drm_file *file_priv,
> +		      const struct drm_mode_fb_cmd2 *r, int i,
> +		      const struct drm_format_info *info)
> +{
> +	struct drm_gem_object *obj;
> +	int bpp = info->cpp[0] * 8;
> +	int tiles;
> +	u32 w, h, height, tile_sz, afbc_size;
> +	int result = 0;
> +
> +	if (i) {
> +		DRM_DEBUG_KMS("AFBC supported only for plane 0\n");
> +
> +		return 1;
> +	}
> +
> +	/* get tile w/h */
> +	if (!drm_afbc_get_superblk_wh(r->modifier[0], &w, &h))
> +		return 1;
> +
> +	/* pitch must be divisible by tile width */
> +	if (r->pitches[0] % w) {
> +		DRM_DEBUG_KMS("Invalid pitch for plane %d\n", i);
> +
> +		return 1;
> +	}
> +
> +	obj = drm_gem_object_lookup(file_priv, r->handles[0]);

I think this is a bit ugly ... I'd split this into a new
framebuffer_check_post() function which is called after fb_create, at that
point you do have the objects already looked up.

Also I suggested that this could be done as a helper implementation for
fb_create, wrapping it around the default gem implementation. That way you
could keep all the afbc stuff in helpers entirely (but drivers could screw
things up, so there's a tradeoff).

What's definitely not ok is calling drm_gem_object_lookup unconditionally
from core code here. For consistency I think the helper approach would be
good, since currently the size related checks are done in
drm_gem_fb_create() - i.e. in the helpers, not in core. Otoh having checks
split like this is also ugly, so maybe we should have a
framebuffer_check_post for everyone, and move all the size checks into
core (not just for afbc).
-Daniel

> +	if (!obj) {
> +		DRM_DEBUG_KMS("Failed to lookup GEM object\n");
> +
> +		return 1;
> +	}
> +
> +	/* estimate height based on tile size and height from userspace */
> +	height = DIV_ROUND_UP(r->height, h) * h;
> +
> +	tiles = (r->pitches[0] / w) * (height / h);
> +	afbc_size = ALIGN(tiles * AFBC_HEADER_SIZE, AFBC_SUPERBLK_ALIGNMENT);
> +
> +	tile_sz = (bpp * w * h) / BITS_PER_BYTE;
> +	afbc_size += tiles * ALIGN(tile_sz, AFBC_SUPERBLK_ALIGNMENT);
> +
> +	result = obj->size < afbc_size;
> +
> +	drm_gem_object_put_unlocked(obj);
> +
> +	return result;
> +}
> +
> +static int modifier_check(struct drm_file *file_priv,
> +			  const struct drm_mode_fb_cmd2 *r, int i,
> +			  const struct drm_format_info *info)
> +{
> +	/* non-afbc format */
> +	if (!drm_is_afbc(r->modifier[i]))
> +		return 0;
> +
> +	return afbc_check(file_priv, r, i, info);
> +}
> +
>  static int framebuffer_check(struct drm_device *dev,
> +			     struct drm_file *file_priv,
>  			     const struct drm_mode_fb_cmd2 *r)
>  {
>  	const struct drm_format_info *info;
> @@ -204,6 +268,9 @@ static int framebuffer_check(struct drm_device *dev,
>  		unsigned int block_size = info->char_per_block[i];
>  		u64 min_pitch = drm_format_info_min_pitch(info, i, width);
>  
> +		if (drm_is_afbc(r->modifier[i]))
> +			block_size = 0;
> +
>  		if (!block_size && (r->modifier[i] == DRM_FORMAT_MOD_LINEAR)) {
>  			DRM_DEBUG_KMS("Format requires non-linear modifier for plane %d\n", i);
>  			return -EINVAL;
> @@ -253,6 +320,8 @@ static int framebuffer_check(struct drm_device *dev,
>  			break;
>  
>  		default:
> +			if (modifier_check(file_priv, r, i, info))
> +				return -EINVAL;
>  			break;
>  		}
>  	}
> @@ -317,7 +386,7 @@ drm_internal_framebuffer_create(struct drm_device *dev,
>  		return ERR_PTR(-EINVAL);
>  	}
>  
> -	ret = framebuffer_check(dev, r);
> +	ret = framebuffer_check(dev, file_priv, r);
>  	if (ret)
>  		return ERR_PTR(ret);
>  
> diff --git a/include/drm/drm_afbc.h b/include/drm/drm_afbc.h
> new file mode 100644
> index 000000000000..fb4d4549f77e
> --- /dev/null
> +++ b/include/drm/drm_afbc.h
> @@ -0,0 +1,35 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * (C) 2019 Collabora Ltd.
> + *
> + * author: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> + *
> + */
> +#ifndef __DRM_AFBC_H__
> +#define __DRM_AFBC_H__
> +
> +#include <linux/types.h>
> +
> +struct drm_device;
> +struct drm_mode_fb_cmd2;
> +struct drm_gem_object;
> +
> +struct drm_afbc {
> +	u32 tile_w;
> +	u32 tile_h;
> +	u32 width;
> +	u32 height;
> +	u32 offset;
> +};
> +
> +#define AFBC_HEADER_SIZE		16
> +#define AFBC_SUPERBLK_ALIGNMENT		128
> +
> +bool drm_afbc_get_superblk_wh(u64 modifier, u32 *w, u32 *h);
> +
> +void drm_afbc_get_parameters(const struct drm_mode_fb_cmd2 *mode_cmd,
> +			     struct drm_afbc *afbc);
> +
> +bool drm_is_afbc(u64 modifier);
> +
> +#endif /* __DRM_AFBC_H__ */
> -- 
> 2.17.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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