Re: [PATCH v4 02/10] drm/i915/dsb: DSB context creation.

["Sharma, Shashank" <shashank.sharma@intel.com>]

> -----Original Message-----
> From: Intel-gfx [mailto:intel-gfx-bounces@lists.freedesktop.org] On Behalf Of Jani
> Nikula
> Sent: Friday, August 30, 2019 7:06 PM
> To: Manna, Animesh <animesh.manna@intel.com>; intel-gfx@lists.freedesktop.org
> Cc: Thierry, Michel <michel.thierry@intel.com>
> Subject: Re: [Intel-gfx] [PATCH v4 02/10] drm/i915/dsb: DSB context creation.
> 
> On Fri, 30 Aug 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)
> >
> > 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>
> > 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      | 83 +++++++++++++++++++
> >  drivers/gpu/drm/i915/display/intel_dsb.h      | 31 +++++++
> >  drivers/gpu/drm/i915/i915_drv.h               |  1 +
> >  5 files changed, 119 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 61277a87dbe7..da36867189cb 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[MAX_DSB_PER_PIPE];
> >  };
> >
> >  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..007ef13481d5
> > --- /dev/null
> > +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> > @@ -0,0 +1,83 @@
> > +// 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;
> > +	intel_wakeref_t wakeref;
> > +	int i;
> > +
> > +	for (i = 0; i < MAX_DSB_PER_PIPE; i++)
> > +		if (!crtc->dsb[i].cmd_buf)
> > +			break;
> > +
> > +	if (WARN_ON(i == MAX_DSB_PER_PIPE))
> > +		return NULL;
> > +
> > +	dsb = &crtc->dsb[i];
> > +	dsb->id = i;
> > +	dsb->crtc = crtc;
> > +	if (!HAS_DSB(i915))
> > +		return dsb;
> 
> Why do you go through any of the trouble if there is no DSB? Just early return NULL,
> and make the write functions handle NULL dsb pointer.
> 
I agree on this. Even I thought it would be better if we populate the DSB ptr only when we find a valid DSB support on the platform. And the caller of get() can understand this and act accordingly. 
> > +
> > +	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;
> > +	struct drm_i915_private *i915;
> > +
> > +	if (!dsb)
> > +		return;
> > +
> > +	crtc = dsb->crtc;
> > +	i915 = to_i915(crtc->base.dev);
> > +
> > +	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);
> > +		dsb->cmd_buf = NULL;
> > +		mutex_unlock(&i915->drm.struct_mutex);
> > +	}
> > +}
> > 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..4a4091cadc1e
> > --- /dev/null
> > +++ b/drivers/gpu/drm/i915/display/intel_dsb.h
> > @@ -0,0 +1,31 @@
> > +/* 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 {
> > +	struct intel_crtc *crtc;
> > +	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 804bfe7aec2b..7aa11e3dd413
> > 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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