Re: [PATCH v6 02/10] drm/i915/dsb: DSB context creation.

[Jani Nikula <jani.nikula@intel.com>]

On Thu, 12 Sep 2019, Animesh Manna <animesh.manna@intel.com> wrote:
> This patch adds a function, which will internally get the gem buffer
> for DSB engine. The GEM buffer is from global GTT, and is mapped into
> CPU domain, contains the data + opcode to be feed to DSB engine.
>
> v1: Initial version.
>
> v2:
> - removed some unwanted code. (Chris)
> - Used i915_gem_object_create_internal instead of _shmem. (Chris)
> - cmd_buf_tail removed and can be derived through vma object. (Chris)
>
> v3: vma realeased if i915_gem_object_pin_map() failed. (Shashank)
>
> v4: for simplification and based on current usage added single dsb
> object in intel_crtc. (Shashank)
>
> v5: seting NULL to cmd_buf moved outside of mutex in dsb-put(). (Shashank)
>
> Cc: Imre Deak <imre.deak@intel.com>
> Cc: Michel Thierry <michel.thierry@intel.com>
> Cc: Jani Nikula <jani.nikula@intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: Shashank Sharma <shashank.sharma@intel.com>
> Signed-off-by: Animesh Manna <animesh.manna@intel.com>
> ---
>  drivers/gpu/drm/i915/Makefile                 |  1 +
>  .../drm/i915/display/intel_display_types.h    |  3 +
>  drivers/gpu/drm/i915/display/intel_dsb.c      | 70 +++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_dsb.h      | 30 ++++++++
>  drivers/gpu/drm/i915/i915_drv.h               |  1 +
>  5 files changed, 105 insertions(+)
>  create mode 100644 drivers/gpu/drm/i915/display/intel_dsb.c
>  create mode 100644 drivers/gpu/drm/i915/display/intel_dsb.h
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 658b930d34a8..6313e7b4bd78 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -172,6 +172,7 @@ i915-y += \
>  	display/intel_display_power.o \
>  	display/intel_dpio_phy.o \
>  	display/intel_dpll_mgr.o \
> +	display/intel_dsb.o \
>  	display/intel_fbc.o \
>  	display/intel_fifo_underrun.o \
>  	display/intel_frontbuffer.o \
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index d5cc4b810d9e..49c902b00484 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1033,6 +1033,9 @@ struct intel_crtc {
>  
>  	/* scalers available on this crtc */
>  	int num_scalers;
> +
> +	/* per pipe DSB related info */
> +	struct intel_dsb dsb;
>  };
>  
>  struct intel_plane {
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.c b/drivers/gpu/drm/i915/display/intel_dsb.c
> new file mode 100644
> index 000000000000..7c1b1574788c
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2019 Intel Corporation
> + *
> + */
> +
> +#include "i915_drv.h"
> +#include "intel_display_types.h"
> +
> +#define DSB_BUF_SIZE    (2 * PAGE_SIZE)
> +
> +struct intel_dsb *
> +intel_dsb_get(struct intel_crtc *crtc)
> +{
> +	struct drm_device *dev = crtc->base.dev;
> +	struct drm_i915_private *i915 = to_i915(dev);
> +	struct drm_i915_gem_object *obj;
> +	struct i915_vma *vma;
> +	struct intel_dsb *dsb = &crtc->dsb;
> +	intel_wakeref_t wakeref;
> +
> +	if ((!HAS_DSB(i915)) || dsb->cmd_buf)
> +		return dsb;

This might work now, but this is racy.

> +
> +	dsb->id = DSB1;
> +	wakeref = intel_runtime_pm_get(&i915->runtime_pm);
> +
> +	obj = i915_gem_object_create_internal(i915, DSB_BUF_SIZE);
> +	if (IS_ERR(obj))
> +		goto err;
> +
> +	mutex_lock(&i915->drm.struct_mutex);
> +	vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, PIN_MAPPABLE);
> +	mutex_unlock(&i915->drm.struct_mutex);
> +	if (IS_ERR(vma)) {
> +		DRM_ERROR("Vma creation failed\n");
> +		i915_gem_object_put(obj);
> +		goto err;
> +	}
> +
> +	dsb->cmd_buf = i915_gem_object_pin_map(vma->obj, I915_MAP_WC);
> +	if (IS_ERR(dsb->cmd_buf)) {
> +		DRM_ERROR("Command buffer creation failed\n");
> +		i915_vma_unpin_and_release(&vma, 0);
> +		dsb->cmd_buf = NULL;
> +		goto err;
> +	}
> +	dsb->vma = vma;
> +
> +err:
> +	intel_runtime_pm_put(&i915->runtime_pm, wakeref);
> +	return dsb;
> +}
> +
> +void intel_dsb_put(struct intel_dsb *dsb)
> +{
> +	struct intel_crtc *crtc = container_of(dsb, typeof(*crtc), dsb);
> +	struct drm_i915_private *i915 = to_i915(crtc->base.dev);
> +
> +	if (!dsb)
> +		return;

If dsb == NULL, the above dereference probably oopses before this check.

BR,
Jani.

> +
> +	if (dsb->cmd_buf) {
> +		mutex_lock(&i915->drm.struct_mutex);
> +		i915_gem_object_unpin_map(dsb->vma->obj);
> +		i915_vma_unpin_and_release(&dsb->vma, 0);
> +		mutex_unlock(&i915->drm.struct_mutex);
> +		dsb->cmd_buf = NULL;
> +	}
> +}
> diff --git a/drivers/gpu/drm/i915/display/intel_dsb.h b/drivers/gpu/drm/i915/display/intel_dsb.h
> new file mode 100644
> index 000000000000..27eb68eb5392
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: MIT
> + *
> + * Copyright © 2019 Intel Corporation
> + */
> +
> +#ifndef _INTEL_DSB_H
> +#define _INTEL_DSB_H
> +
> +struct intel_crtc;
> +struct i915_vma;
> +
> +enum dsb_id {
> +	INVALID_DSB = -1,
> +	DSB1,
> +	DSB2,
> +	DSB3,
> +	MAX_DSB_PER_PIPE
> +};
> +
> +struct intel_dsb {
> +	enum dsb_id id;
> +	u32 *cmd_buf;
> +	struct i915_vma *vma;
> +};
> +
> +struct intel_dsb *
> +intel_dsb_get(struct intel_crtc *crtc);
> +void intel_dsb_put(struct intel_dsb *dsb);
> +
> +#endif
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 6c6af007f29d..069a06edb5c6 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -67,6 +67,7 @@
>  #include "display/intel_display.h"
>  #include "display/intel_display_power.h"
>  #include "display/intel_dpll_mgr.h"
> +#include "display/intel_dsb.h"
>  #include "display/intel_frontbuffer.h"
>  #include "display/intel_gmbus.h"
>  #include "display/intel_opregion.h"

-- 
Jani Nikula, Intel Open Source Graphics Center
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