diff mbox series

[v3,02/11] drm/i915/dsb: DSB context creation.

Message ID 20190827191026.26175-3-animesh.manna@intel.com (mailing list archive)
State New, archived
Headers show
Series DSB enablement. | expand

Commit Message

Manna, Animesh Aug. 27, 2019, 7:10 p.m. UTC
The function will internally get the gem buffer from global GTT
which is mapped in cpu domain to feed the data + opcode for 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)

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

Comments

Sharma, Shashank Aug. 28, 2019, 2:39 p.m. UTC | #1
On 8/28/2019 12:40 AM, Animesh Manna wrote:
> The function will internally get the gem buffer from global GTT
This patch adds a function, which will internally get the gem buffer for 
DSB engine.
> which is mapped in cpu domain to feed the data + opcode for DSB engine.
This GEM buffer is from global GTT, and is mapped into CPU domain, 
contains the data + opcode to be fed 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)
>
> 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 96514dcc7812..0ab3516b0044 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1026,6 +1026,9 @@ 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..a2845df90573
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2019 Intel Corporation
> + *
> + */
> +
Any particular reason we don't have the traditional license here, like 
other files ?
> +#include "../i915_drv.h"
This is not the way you should include this header. Take example from 
other files in display folder.
> +#include "intel_display_types.h"
> +
> +#define DSB_BUF_SIZE    (2 * PAGE_SIZE)
Any particular reason for this 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;
> +
> +	WARN_ON(i >= MAX_DSB_PER_PIPE);

Its not possible to have i > MAX_DSB_PER_PIPE as per above logic, so it 
should be WARN_ON(i == MAX_DSB_PER_PIPE);

Also, shouldn't we stop operation here (along with the warning) as 
clearly the cmd_buf and dsb we are going to get, is garbage ? On 
negative testing this may cause kernel panic also.

> +
> +	dsb = &crtc->dsb[i];
> +	dsb->id = i;
> +	dsb->crtc = crtc;
> +	if (!HAS_DSB(i915))
> +		return dsb;
This check should be the first line in this function. I am not sure why 
do we want to extract dsb ptr if the platform doesn't even support DSB.
> +
> +	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_DEBUG_KMS("Vma creation failed.\n");
> +		i915_gem_object_put(obj);
Shouldn't gem_object_put() be inside mutex ?
> +		goto err;
> +	}
> +
> +	dsb->cmd_buf = i915_gem_object_pin_map(vma->obj, I915_MAP_WC);
> +	if (IS_ERR(dsb->cmd_buf)) {
> +		DRM_DEBUG_KMS("Command buffer creation failed.\n");
> +		dsb->cmd_buf = NULL;
Why don't we have a i915_gem_object_put(obj) here ?
> +		goto err;
> +	}
> +	dsb->vma = vma;
> +
> +err:
I think we should have a i915_gem_object_put(obj) for all error cases here.
> +	intel_runtime_pm_put(&i915->runtime_pm, wakeref);
> +	return dsb;
Again, we are returning a dsb ptr in all cases. As this patch doesn't 
have the caller function, I can't understand why are we returning the 
same ptr in both success or failure cases, but I would prefer a 
dsb_get() function which returns NULL on failure, dsb* on success.
> +}
> +
> +void intel_dsb_put(struct intel_dsb *dsb)
> +{
> +	struct intel_crtc *crtc;
> +	struct drm_i915_private *i915;
> +	struct i915_vma *vma;
> +
> +	if (!dsb)
> +		return;
So the get() API returns a non-NULL pointer in both success and failure 
cases, but put() can have a NULL ptr as input. Looks a bit asymmetrical  
design. Also, we should add API documentation on top of the function 
now, as we need to understand what can be the return values of the 
function.
> +
> +	crtc = dsb->crtc;
> +	i915 = to_i915(crtc->base.dev);
> +
> +	if (dsb->cmd_buf) {
> +		vma = dsb->vma;
> +		mutex_lock(&i915->drm.struct_mutex);
> +		i915_gem_object_unpin_map(vma->obj);
> +		i915_vma_unpin_and_release(&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
Same as above for license.
> + */
> +
> +#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
The Bspec says there are 3 DSB DMA engines per pipe, and we have defined 
MAX_DSB_PER_PIPE = 3 (and the count starts from 0), which means we 
should be running our loops always < MAX_DSB_PER_PIPE. I would prefer 
this to be either INVALID_DSB = 0 and DSB3 = MAX_DSB = 3, but this is 
just a soft requirement, you can pick or ignore.
> +};
> +
> +struct intel_dsb {
> +	struct intel_crtc *crtc;
> +	enum dsb_id id;
Note that your INVALID_DSB id is -1 not 0. This means all the intel_dsb 
structures will be initialized with id=DSB1 not INVALID_DSB.
> +	u32 *cmd_buf;
> +	struct i915_vma *vma;
> +};
> +
This could also be the place to add doc about the get/put functions.
> +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 d32cfdb78b74..dd6cfb89b830 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"

No external element is using get() / put() functions yet, this change 
should go into a patch, which is using the functions.

- Shashank

>   #include "display/intel_frontbuffer.h"
>   #include "display/intel_gmbus.h"
>   #include "display/intel_opregion.h"
Manna, Animesh Aug. 29, 2019, 10:40 a.m. UTC | #2
Hi,


On 8/28/2019 8:09 PM, Sharma, Shashank wrote:
>
> On 8/28/2019 12:40 AM, Animesh Manna wrote:
>> The function will internally get the gem buffer from global GTT
> This patch adds a function, which will internally get the gem buffer 
> for DSB engine.
>> which is mapped in cpu domain to feed the data + opcode for DSB engine.
> This GEM buffer is from global GTT, and is mapped into CPU domain, 
> contains the data + opcode to be fed to DSB engine.

ok.

>>
>> 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)
>>
>> 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 96514dcc7812..0ab3516b0044 100644
>> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
>> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
>> @@ -1026,6 +1026,9 @@ 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..a2845df90573
>> --- /dev/null
>> +++ b/drivers/gpu/drm/i915/display/intel_dsb.c
>> @@ -0,0 +1,83 @@
>> +// SPDX-License-Identifier: MIT
>> +/*
>> + * Copyright © 2019 Intel Corporation
>> + *
>> + */
>> +
> Any particular reason we don't have the traditional license here, like 
> other files ?

Current trend I hope to use SPDX header otherwise checkpatch is throwing 
warning/error.

>> +#include "../i915_drv.h"
> This is not the way you should include this header. Take example from 
> other files in display folder.
#include "i915_drv.h"
rt?
>
>> +#include "intel_display_types.h"
>> +
>> +#define DSB_BUF_SIZE    (2 * PAGE_SIZE)
> Any particular reason for this size ?

one page is not sufficient and do not want to use too many pages.

>
>> +
>> +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;
>> +
>> +    WARN_ON(i >= MAX_DSB_PER_PIPE);
>
> Its not possible to have i > MAX_DSB_PER_PIPE as per above logic, so 
> it should be WARN_ON(i == MAX_DSB_PER_PIPE);

ok.

>
> Also, shouldn't we stop operation here (along with the warning) as 
> clearly the cmd_buf and dsb we are going to get, is garbage ? On 
> negative testing this may cause kernel panic also.

I feel for erroneous case, as DSB is not handled properly, better to 
halt the kernel.
Good idea to return NULL, will do it.

>
>> +
>> +    dsb = &crtc->dsb[i];
>> +    dsb->id = i;
>> +    dsb->crtc = crtc;
>> +    if (!HAS_DSB(i915))
>> +        return dsb;
> This check should be the first line in this function. I am not sure 
> why do we want to extract dsb ptr if the platform doesn't even support 
> DSB.

As per agreed design with Jani we want to replace I915_WRITE with 
dsp-write api for all platform and for older platform will fallback to 
i915_WRITE call.

>> +
>> +    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_DEBUG_KMS("Vma creation failed.\n");
>> +        i915_gem_object_put(obj);
> Shouldn't gem_object_put() be inside mutex ?

Tried to refer existing code to understand the need, may not need it.

>> +        goto err;
>> +    }
>> +
>> +    dsb->cmd_buf = i915_gem_object_pin_map(vma->obj, I915_MAP_WC);
>> +    if (IS_ERR(dsb->cmd_buf)) {
>> +        DRM_DEBUG_KMS("Command buffer creation failed.\n");
>> +        dsb->cmd_buf = NULL;
> Why don't we have a i915_gem_object_put(obj) here ?

Will add in err-section.
>
>> +        goto err;
>> +    }
>> +    dsb->vma = vma;
>> +
>> +err:
> I think we should have a i915_gem_object_put(obj) for all error cases 
> here.

Ok.

>> + intel_runtime_pm_put(&i915->runtime_pm, wakeref);
>> +    return dsb;
> Again, we are returning a dsb ptr in all cases. As this patch doesn't 
> have the caller function, I can't understand why are we returning the 
> same ptr in both success or failure cases, but I would prefer a 
> dsb_get() function which returns NULL on failure, dsb* on success.

Explained above.

>> +}
>> +
>> +void intel_dsb_put(struct intel_dsb *dsb)
>> +{
>> +    struct intel_crtc *crtc;
>> +    struct drm_i915_private *i915;
>> +    struct i915_vma *vma;
>> +
>> +    if (!dsb)
>> +        return;
> So the get() API returns a non-NULL pointer in both success and 
> failure cases, but put() can have a NULL ptr as input. Looks a bit 
> asymmetrical  design. Also, we should add API documentation on top of 
> the function now, as we need to understand what can be the return 
> values of the function.

As discussed will send NULL if user ask for DSB after reaching 
MAX_DSB_PER_PIPE, we can keep the null check.

>> +
>> +    crtc = dsb->crtc;
>> +    i915 = to_i915(crtc->base.dev);
>> +
>> +    if (dsb->cmd_buf) {
>> +        vma = dsb->vma;
>> +        mutex_lock(&i915->drm.struct_mutex);
>> +        i915_gem_object_unpin_map(vma->obj);
>> +        i915_vma_unpin_and_release(&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
> Same as above for license.

Explained above.

>> + */
>> +
>> +#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
> The Bspec says there are 3 DSB DMA engines per pipe, and we have 
> defined MAX_DSB_PER_PIPE = 3 (and the count starts from 0), which 
> means we should be running our loops always < MAX_DSB_PER_PIPE. I 
> would prefer this to be either INVALID_DSB = 0 and DSB3 = MAX_DSB = 3, 
> but this is just a soft requirement, you can pick or ignore.

dsb_id is used to internally to access DSB registers.

>> +};
>> +
>> +struct intel_dsb {
>> +    struct intel_crtc *crtc;
>> +    enum dsb_id id;
> Note that your INVALID_DSB id is -1 not 0. This means all the 
> intel_dsb structures will be initialized with id=DSB1 not INVALID_DSB.

I feel it is similar like enum used for pipe, port etc also not 
expecting any invalid usage.

>> +    u32 *cmd_buf;
>> +    struct i915_vma *vma;
>> +};
>> +
> This could also be the place to add doc about the get/put functions.

Initially added per function basis and as per previous feedback created 
a separate patch only for docbook.

>> +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 d32cfdb78b74..dd6cfb89b830 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"
>
> No external element is using get() / put() functions yet, this change 
> should go into a patch, which is using the functions.

Understood your concern, the change will be little big having all 
dsp-api and its usage together, so splited as per different dsp-api and 
later a separate patch is created to enable gamma through DSB.

Regards,
Animesh

>
> - Shashank
>
>>   #include "display/intel_frontbuffer.h"
>>   #include "display/intel_gmbus.h"
>>   #include "display/intel_opregion.h"
diff mbox series

Patch

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 96514dcc7812..0ab3516b0044 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1026,6 +1026,9 @@  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..a2845df90573
--- /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;
+
+	WARN_ON(i >= MAX_DSB_PER_PIPE);
+
+	dsb = &crtc->dsb[i];
+	dsb->id = i;
+	dsb->crtc = crtc;
+	if (!HAS_DSB(i915))
+		return dsb;
+
+	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_DEBUG_KMS("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_DEBUG_KMS("Command buffer creation failed.\n");
+		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;
+	struct i915_vma *vma;
+
+	if (!dsb)
+		return;
+
+	crtc = dsb->crtc;
+	i915 = to_i915(crtc->base.dev);
+
+	if (dsb->cmd_buf) {
+		vma = dsb->vma;
+		mutex_lock(&i915->drm.struct_mutex);
+		i915_gem_object_unpin_map(vma->obj);
+		i915_vma_unpin_and_release(&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 d32cfdb78b74..dd6cfb89b830 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"