Re: [RFC PATCH 1/1] drm/meson: Support drm_panic

[Neil Armstrong <neil.armstrong@linaro.org>]

Hi !

On 01/10/2024 23:04, Yao Zi wrote:
> This patch implements drm_plane_helper_funcs.get_scanout_buffer for
> primary plane, enabling meson-drm to work with drm_panic.
> 
> This implementation tries to use current framebuffer as scanout buffer.
> In case of AFBC enabled, we disable the decoder path and adjust OSD1
> parameters in get_scanout_buffer to make the buffer linear.
> 
> Tested on TTY and Wayland session (Sway).

Thanks for enabling this!

> 
> Signed-off-by: Yao Zi <ziyao@disroot.org>
> ---
>   drivers/gpu/drm/meson/meson_plane.c | 47 +++++++++++++++++++++++++++--
>   1 file changed, 44 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/meson/meson_plane.c b/drivers/gpu/drm/meson/meson_plane.c
> index b43ac61201f3..b2def784c00d 100644
> --- a/drivers/gpu/drm/meson/meson_plane.c
> +++ b/drivers/gpu/drm/meson/meson_plane.c
> @@ -20,6 +20,8 @@
>   #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_panic.h>
>   
>   #include "meson_plane.h"
>   #include "meson_registers.h"
> @@ -419,10 +421,49 @@ static void meson_plane_atomic_disable(struct drm_plane *plane,
>   	priv->viu.osd1_enabled = false;
>   }
>   
> +static int meson_plane_get_scanout_buffer(struct drm_plane *plane,
> +					  struct drm_scanout_buffer *sb)
> +{
> +	struct meson_plane *meson_plane = to_meson_plane(plane);
> +	struct meson_drm *priv = meson_plane->priv;
> +	struct drm_framebuffer *fb;
> +
> +	if (!meson_plane->enabled)
> +		return -ENODEV;
> +
> +	if (priv->viu.osd1_afbcd) {
> +		if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_GXM)) {

This should be meson_vpu_is_compatible(priv, VPU_COMPATIBLE_G12A)

You should call:

			if (priv->afbcd.ops) {
				priv->afbcd.ops->reset(priv);
				priv->afbcd.ops->disable(priv);
			}

> +			writel_relaxed(0, priv->io_base +
> +					  _REG(VIU_OSD1_BLK1_CFG_W4));
> +			writel_relaxed(0, priv->io_base +
> +					  _REG(VIU_OSD1_BLK2_CFG_W4));
> +			writel_bits_relaxed(OSD_ENDIANNESS_LE, OSD_ENDIANNESS_LE,
> +					    priv->io_base +
> +					    _REG(VIU_OSD1_BLK0_CFG_W0));

This won't work, drop it, the canvas isn't correctly configured, you should instead call:
			meson_canvas_config(priv->canvas, priv->canvas_id_osd1,
					    priv->viu.osd1_addr,
					    priv->viu.osd1_stride,
					    priv->viu.osd1_height,
					    MESON_CANVAS_WRAP_NONE,
					    MESON_CANVAS_BLKMODE_LINEAR, 0);

> +			meson_viu_g12a_disable_osd1_afbc(priv);
> +		} else if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_G12A)) {

And here meson_vpu_is_compatible(priv, VPU_COMPATIBLE_GXM)

> +			writel_bits_relaxed(OSD_DPATH_MALI_AFBCD, 0,
> +					    priv->io_base +
> +					    _REG(VIU_OSD1_CTRL_STAT2));

Ok, you should also call meson_canvas_config()

You should call:

			if (priv->afbcd.ops) {
				priv->afbcd.ops->reset(priv);
				priv->afbcd.ops->disable(priv);
			}

> +			meson_viu_gxm_disable_osd1_afbc(priv);
> +		}
> +	}

I thing the code should look like:

if (priv->viu.osd1_afbcd) {
	meson_canvas_config(priv->canvas, priv->canvas_id_osd1,
			    priv->viu.osd1_addr,
			    priv->viu.osd1_stride,
			    priv->viu.osd1_height,
			    MESON_CANVAS_WRAP_NONE,
			    MESON_CANVAS_BLKMODE_LINEAR, 0);

	if (priv->afbcd.ops) {
		priv->afbcd.ops->reset(priv);
		priv->afbcd.ops->disable(priv);
	}

	if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_G12A)) {
		writel_bits_relaxed(OSD_ENDIANNESS_LE, OSD_ENDIANNESS_LE,
				    priv->io_base +
				    _REG(VIU_OSD1_BLK0_CFG_W0));
		meson_viu_g12a_disable_osd1_afbc(priv);
	} else if (meson_vpu_is_compatible(priv, VPU_COMPATIBLE_GXM)) {
		writel_bits_relaxed(OSD_DPATH_MALI_AFBCD, 0,
				    priv->io_base +
				    _REG(VIU_OSD1_CTRL_STAT2));
		meson_viu_gxm_disable_osd1_afbc(priv);
	}
}

AFBC is quite hard to test since it requires DRM_FORMAT_XBGR8888, but
I think sway should perhaps support it, Mesa should also support AFBC.

At some point I made some memory dumps of AFBC buffers, perhaps they could
be useful here.

Another way would be to simply ignore the AFBC case, and bail out since
it would be a very rare case.

> +
> +	fb = plane->state->fb;
> +	sb->format	= fb->format;
> +	sb->width	= fb->width;
> +	sb->height	= fb->height;
> +	sb->pitch[0]	= fb->pitches[0];
> +	drm_gem_fb_vmap(fb, sb->map, NULL);
> +
> +	return 0;
> +}
> +
>   static const struct drm_plane_helper_funcs meson_plane_helper_funcs = {
> -	.atomic_check	= meson_plane_atomic_check,
> -	.atomic_disable	= meson_plane_atomic_disable,
> -	.atomic_update	= meson_plane_atomic_update,
> +	.atomic_check		= meson_plane_atomic_check,
> +	.atomic_disable		= meson_plane_atomic_disable,
> +	.atomic_update		= meson_plane_atomic_update,
> +	.get_scanout_buffer	= meson_plane_get_scanout_buffer,
>   };
>   
>   static bool meson_plane_format_mod_supported(struct drm_plane *plane,

Thanks,
Neil