[v2 0/2] drm/i915/display: Implement Display Wa_16030862157

[v2 0/2] drm/i915/display: Implement Display Wa_16030862157

[Uma Shankar]

Interpret 0xF populated-channel count as 16. For 16-channel
configuration, BIOS programs 1111b. A programmed value of 1111b
must be interpreted as 16 channels for memory bandwidth calculations.
This series implements the workaround in driver.

Uma Shankar (2):
  drm/i915/display: Add Wa_16030862157 to the display workaround list
  drm/i915/dram: Interpret 0xF populated-channel count as 16

 drivers/gpu/drm/i915/display/intel_bw.c       | 20 ++++++++++++++++---
 .../gpu/drm/i915/display/intel_display_wa.c   |  2 ++
 .../gpu/drm/i915/display/intel_display_wa.h   |  1 +
 drivers/gpu/drm/i915/display/intel_dram.c     | 12 +++++++++++
 4 files changed, 32 insertions(+), 3 deletions(-)

-- 
2.50.1

[v2 1/2] drm/i915/display: Add Wa_16030862157 to the display workaround list

[Uma Shankar]

Register Wa_16030862157 in the display workaround framework so that its
platform applicability lives in one place (__intel_display_wa()) rather
than being open-coded at each use site. The workaround applies to Xe3p
(DISPLAY_VER >= 35).

No functional change: this only adds the enum entry and the matching
case; consumers are wired up in a follow-up change.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
---
 drivers/gpu/drm/i915/display/intel_display_wa.c | 2 ++
 drivers/gpu/drm/i915/display/intel_display_wa.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.c b/drivers/gpu/drm/i915/display/intel_display_wa.c
index b4c49816f7eb..d6b036da3992 100644
--- a/drivers/gpu/drm/i915/display/intel_display_wa.c
+++ b/drivers/gpu/drm/i915/display/intel_display_wa.c
@@ -140,6 +140,8 @@ bool __intel_display_wa(struct intel_display *display, enum intel_display_wa wa,
 						STEP_A0, STEP_B0);
 	case INTEL_DISPLAY_WA_16029024088:
 		return DISPLAY_VER(display) >= 35;
+	case INTEL_DISPLAY_WA_16030862157:
+		return DISPLAY_VER(display) >= 35;
 	case INTEL_DISPLAY_WA_18034343758:
 		return DISPLAY_VER(display) == 20 ||
 			(display->platform.pantherlake &&
diff --git a/drivers/gpu/drm/i915/display/intel_display_wa.h b/drivers/gpu/drm/i915/display/intel_display_wa.h
index 92b3980bea84..338b32e4162d 100644
--- a/drivers/gpu/drm/i915/display/intel_display_wa.h
+++ b/drivers/gpu/drm/i915/display/intel_display_wa.h
@@ -54,6 +54,7 @@ enum intel_display_wa {
 	INTEL_DISPLAY_WA_16025573575,
 	INTEL_DISPLAY_WA_16025596647,
 	INTEL_DISPLAY_WA_16029024088,
+	INTEL_DISPLAY_WA_16030862157,
 	INTEL_DISPLAY_WA_18034343758,
 	INTEL_DISPLAY_WA_22010178259,
 	INTEL_DISPLAY_WA_22010947358,
-- 
2.50.1

[v2 2/2] drm/i915/dram: Interpret 0xF populated-channel count as 16

[Uma Shankar]

The register MEM_SS_INFO_GLOBAL [Number of populated channels] field
definition is updated with an encoding for 16 channels.

For 16-channel configuration, program 1111b. A programmed value of 1111b
must be interpreted as 16 channels for memory bandwidth calculations.

The MEM_SS_INFO_GLOBAL populated-channel field is only 4 bits and cannot
encode 16, so on Xe3p the BIOS programs the saturated field value (0xf)
to indicate the fully-populated 16-channel config (4 memory controllers
x 4 channels). Interpret it as 16 and let the bandwidth math handle the
larger channel count.

Gate the behaviour through intel_display_wa(INTEL_DISPLAY_WA_16030862157)
instead of an open-coded DISPLAY_VER() check.

v2: Switched to intel_display_wa.c framework (Suraj)

WA: 16030862157
Bspec: 69131, 68859
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
---
 drivers/gpu/drm/i915/display/intel_bw.c   | 20 +++++++++++++++++---
 drivers/gpu/drm/i915/display/intel_dram.c | 12 ++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_bw.c b/drivers/gpu/drm/i915/display/intel_bw.c
index 41539fdfeac5..aaa0350dca78 100644
--- a/drivers/gpu/drm/i915/display/intel_bw.c
+++ b/drivers/gpu/drm/i915/display/intel_bw.c
@@ -14,6 +14,7 @@
 #include "intel_display_regs.h"
 #include "intel_display_types.h"
 #include "intel_display_utils.h"
+#include "intel_display_wa.h"
 #include "intel_dram.h"
 #include "intel_mchbar.h"
 #include "intel_parent.h"
@@ -272,7 +273,14 @@ static int icl_get_qgv_points(struct intel_display *display,
 		case INTEL_DRAM_LPDDR4:
 		case INTEL_DRAM_LPDDR5:
 			qi->t_bl = 16;
-			qi->max_numchannels = 8;
+			/*
+			 * Wa_16030862157
+			 * Xe3p supports a fully-populated 16-channel LPDDR
+			 * config (4 memory controllers x 4 channels); earlier
+			 * D14+ platforms top out at 8.
+			 */
+			qi->max_numchannels =
+				intel_display_wa(display, INTEL_DISPLAY_WA_16030862157) ? 16 : 8;
 			qi->channel_width = 16;
 			qi->deinterleave = 4;
 			break;
@@ -624,10 +632,16 @@ static int tgl_get_bw_info(struct intel_display *display,
 
 	ipqdepth = min(ipqdepthpch, display_bw_params->displayrtids / num_channels);
 	/*
+	 * Wa_16030862157
 	 * clperchgroup = 4kpagespermempage * clperchperblock,
-	 * clperchperblock = 8 / num_channels * interleave
+	 * clperchperblock = max(8 / num_channels, 1) * interleave
+	 *
+	 * The 8 / num_channels truncating divide collapses to 0 for
+	 * >8-channel configs (16-channel: 8 / 16 = 0); the max(..., 1) floor
+	 * keeps clperchperblock >= 1 there while preserving the literal
+	 * truncating divide for <=8-channel configs.
 	 */
-	clperchgroup = 4 * (8 / num_channels) * qi.deinterleave;
+	clperchgroup = 4 * max(8 / num_channels, 1) * qi.deinterleave;
 
 	display->bw.num_qgv_points = qi.num_qgv_points;
 	display->bw.num_psf_gv_points = qi.num_psf_points;
diff --git a/drivers/gpu/drm/i915/display/intel_dram.c b/drivers/gpu/drm/i915/display/intel_dram.c
index f103f7cba018..7e2fc24e240c 100644
--- a/drivers/gpu/drm/i915/display/intel_dram.c
+++ b/drivers/gpu/drm/i915/display/intel_dram.c
@@ -13,6 +13,7 @@
 #include "intel_display_core.h"
 #include "intel_display_utils.h"
 #include "intel_display_regs.h"
+#include "intel_display_wa.h"
 #include "intel_dram.h"
 #include "intel_mchbar.h"
 #include "intel_parent.h"
@@ -796,6 +797,17 @@ static int xelpdp_get_dram_info(struct intel_display *display, struct dram_info
 	dram_info->num_qgv_points = REG_FIELD_GET(MTL_N_OF_ENABLED_QGV_POINTS_MASK, val);
 	/* PSF GV points not supported in D14+ */
 
+	/*
+	 * Wa_16030862157
+	 * MEM_SS_INFO_GLOBAL populated-channel field is only 4 bits and
+	 * cannot encode 16, so on Xe3p the BIOS programs the saturated field
+	 * value (0xf) to indicate the fully-populated 16-channel config (4
+	 * memory controllers x 4 channels). Interpret it as 16.
+	 */
+	if (intel_display_wa(display, INTEL_DISPLAY_WA_16030862157) &&
+	    dram_info->num_channels == REG_FIELD_MAX(MTL_N_OF_POPULATED_CH_MASK))
+		dram_info->num_channels = 16;
+
 	if (DISPLAY_VER(display) >= 35)
 		dram_info->ecc_impacting_de_bw = REG_FIELD_GET(XE3P_ECC_IMPACTING_DE, val);
 
-- 
2.50.1

✓ i915.CI.BAT: success for drm/i915/display: Implement Display Wa_16030862157

[Patchwork]

[-- Attachment #1: Type: text/plain, Size: 1111 bytes --]

== Series Details ==

Series: drm/i915/display: Implement Display Wa_16030862157
URL   : https://patchwork.freedesktop.org/series/170473/
State : success

== Summary ==

CI Bug Log - changes from CI_DRM_18827 -> Patchwork_170473v1
====================================================

Summary
-------

  **SUCCESS**

  No regressions found.

  External URL: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_170473v1/index.html

Participating hosts (41 -> 38)
------------------------------

  Missing    (3): bat-dg2-13 fi-snb-2520m bat-adls-6 


Changes
-------

  No changes found


Build changes
-------------

  * Linux: CI_DRM_18827 -> Patchwork_170473v1

  CI-20190529: 20190529
  CI_DRM_18827: 6dd678fdc2f39062bed466d7e3c851736e376531 @ git://anongit.freedesktop.org/gfx-ci/linux
  IGT_9006: 6380a8af26359dd222e22679442272ded836c463 @ https://gitlab.freedesktop.org/drm/igt-gpu-tools.git
  Patchwork_170473v1: 6dd678fdc2f39062bed466d7e3c851736e376531 @ git://anongit.freedesktop.org/gfx-ci/linux

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_170473v1/index.html

[-- Attachment #2: Type: text/html, Size: 1676 bytes --]

✓ i915.CI.Full: success for drm/i915/display: Implement Display Wa_16030862157

[Patchwork]

[-- Attachment #1: Type: text/plain, Size: 1114 bytes --]

== Series Details ==

Series: drm/i915/display: Implement Display Wa_16030862157
URL   : https://patchwork.freedesktop.org/series/170473/
State : success

== Summary ==

CI Bug Log - changes from CI_DRM_18827_full -> Patchwork_170473v1_full
====================================================

Summary
-------

  **SUCCESS**

  No regressions found.

  

Participating hosts (10 -> 10)
------------------------------

  No changes in participating hosts


Changes
-------

  No changes found


Build changes
-------------

  * Linux: CI_DRM_18827 -> Patchwork_170473v1

  CI-20190529: 20190529
  CI_DRM_18827: 6dd678fdc2f39062bed466d7e3c851736e376531 @ git://anongit.freedesktop.org/gfx-ci/linux
  IGT_9006: 6380a8af26359dd222e22679442272ded836c463 @ https://gitlab.freedesktop.org/drm/igt-gpu-tools.git
  Patchwork_170473v1: 6dd678fdc2f39062bed466d7e3c851736e376531 @ git://anongit.freedesktop.org/gfx-ci/linux
  piglit_4509: fdc5a4ca11124ab8413c7988896eec4c97336694 @ git://anongit.freedesktop.org/piglit

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_170473v1/index.html

[-- Attachment #2: Type: text/html, Size: 1677 bytes --]

Re: [v2 2/2] drm/i915/dram: Interpret 0xF populated-channel count as 16

[Govindapillai, Vinod]

Hi Uma,

On Wed, 2026-07-15 at 16:11 +0530, Uma Shankar wrote:
> The register MEM_SS_INFO_GLOBAL [Number of populated channels] field
> definition is updated with an encoding for 16 channels.
> 
> For 16-channel configuration, program 1111b. A programmed value of
> 1111b
> must be interpreted as 16 channels for memory bandwidth calculations.
> 
> The MEM_SS_INFO_GLOBAL populated-channel field is only 4 bits and
> cannot
> encode 16, so on Xe3p the BIOS programs the saturated field value
> (0xf)
> to indicate the fully-populated 16-channel config (4 memory
> controllers
> x 4 channels). Interpret it as 16 and let the bandwidth math handle
> the
> larger channel count.
> 
> Gate the behaviour through
> intel_display_wa(INTEL_DISPLAY_WA_16030862157)
> instead of an open-coded DISPLAY_VER() check.
> 
> v2: Switched to intel_display_wa.c framework (Suraj)
> 
> WA: 16030862157
> Bspec: 69131, 68859
> Assisted-by: Claude:claude-opus-4-8
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_bw.c   | 20 +++++++++++++++++---
>  drivers/gpu/drm/i915/display/intel_dram.c | 12 ++++++++++++
>  2 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_bw.c
> b/drivers/gpu/drm/i915/display/intel_bw.c
> index 41539fdfeac5..aaa0350dca78 100644
> --- a/drivers/gpu/drm/i915/display/intel_bw.c
> +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> @@ -14,6 +14,7 @@
>  #include "intel_display_regs.h"
>  #include "intel_display_types.h"
>  #include "intel_display_utils.h"
> +#include "intel_display_wa.h"
>  #include "intel_dram.h"
>  #include "intel_mchbar.h"
>  #include "intel_parent.h"
> @@ -272,7 +273,14 @@ static int icl_get_qgv_points(struct
> intel_display *display,
>  		case INTEL_DRAM_LPDDR4:
>  		case INTEL_DRAM_LPDDR5:
>  			qi->t_bl = 16;
> -			qi->max_numchannels = 8;
> +			/*
> +			 * Wa_16030862157
> +			 * Xe3p supports a fully-populated 16-
> channel LPDDR
> +			 * config (4 memory controllers x 4
> channels); earlier
> +			 * D14+ platforms top out at 8.
> +			 */
> +			qi->max_numchannels =
> +				intel_display_wa(display,
> INTEL_DISPLAY_WA_16030862157) ? 16 : 8;

As per the bspec 68859, max channel of 16 v. 8 is based on a specific
sku. Do we have any further info on that how to variate that?

But the INTEL_DISPLAY_WA_16030862157 applies to display versions >= 35 

In tgl_get_bw_info(), we have this adjustment to the deinterleave

	if (num_channels < qi.max_numchannels && DISPLAY_VER(display)
>= 12)
		qi.deinterleave = max(qi.deinterleave / 2, 1);

So with the above change we will always end up in this loop and adjust
the qi.deinterleave for all versions >= 35 not just the specific "sku"
which I think is not correct. May be need to check from the IP team or
clarify/update the bspec?

And another suggestion for your consideration is:

I didnt find this 1603862157 as part of wa database. Is there any wa
bspec? So do we need to  implement this as a wa?

If this is considered as a wa:

If I understand this correctly, wa is mainly about part where bios
populate the MTL_N_OF_POPULATED_CH_MASK fields as 0xf in cased of
channels 16 and we interpret that as channels = 16 instead of 15.  

IMO, ideally it is better to split this into two parts, 

1. wa definitions in the existing driver wa framework + changes in
xelpdp_get_dram_info() related to this wa as a single patch like other
wa implementations in the driver so far.

2. Update the bw info changes to add support for max_number of channels
to 16 in case of a specific SKU and the update to the
c9_clperchperblock calculation part.

BR
Vinod


>  			qi->channel_width = 16;
>  			qi->deinterleave = 4;
>  			break;
> @@ -624,10 +632,16 @@ static int tgl_get_bw_info(struct intel_display
> *display,
>  
>  	ipqdepth = min(ipqdepthpch, display_bw_params->displayrtids
> / num_channels);
>  	/*
> +	 * Wa_16030862157
>  	 * clperchgroup = 4kpagespermempage * clperchperblock,
> -	 * clperchperblock = 8 / num_channels * interleave
> +	 * clperchperblock = max(8 / num_channels, 1) * interleave
> +	 *
> +	 * The 8 / num_channels truncating divide collapses to 0 for
> +	 * >8-channel configs (16-channel: 8 / 16 = 0); the max(...,
> 1) floor
> +	 * keeps clperchperblock >= 1 there while preserving the
> literal
> +	 * truncating divide for <=8-channel configs.
>  	 */
> -	clperchgroup = 4 * (8 / num_channels) * qi.deinterleave;
> +	clperchgroup = 4 * max(8 / num_channels, 1) *
> qi.deinterleave;
>  
>  	display->bw.num_qgv_points = qi.num_qgv_points;
>  	display->bw.num_psf_gv_points = qi.num_psf_points;
> diff --git a/drivers/gpu/drm/i915/display/intel_dram.c
> b/drivers/gpu/drm/i915/display/intel_dram.c
> index f103f7cba018..7e2fc24e240c 100644
> --- a/drivers/gpu/drm/i915/display/intel_dram.c
> +++ b/drivers/gpu/drm/i915/display/intel_dram.c
> @@ -13,6 +13,7 @@
>  #include "intel_display_core.h"
>  #include "intel_display_utils.h"
>  #include "intel_display_regs.h"
> +#include "intel_display_wa.h"
>  #include "intel_dram.h"
>  #include "intel_mchbar.h"
>  #include "intel_parent.h"
> @@ -796,6 +797,17 @@ static int xelpdp_get_dram_info(struct
> intel_display *display, struct dram_info
>  	dram_info->num_qgv_points =
> REG_FIELD_GET(MTL_N_OF_ENABLED_QGV_POINTS_MASK, val);
>  	/* PSF GV points not supported in D14+ */
>  
> +	/*
> +	 * Wa_16030862157
> +	 * MEM_SS_INFO_GLOBAL populated-channel field is only 4 bits
> and
> +	 * cannot encode 16, so on Xe3p the BIOS programs the
> saturated field
> +	 * value (0xf) to indicate the fully-populated 16-channel
> config (4
> +	 * memory controllers x 4 channels). Interpret it as 16.
> +	 */
> +	if (intel_display_wa(display, INTEL_DISPLAY_WA_16030862157)
> &&
> +	    dram_info->num_channels ==
> REG_FIELD_MAX(MTL_N_OF_POPULATED_CH_MASK))
> +		dram_info->num_channels = 16;
> +
>  	if (DISPLAY_VER(display) >= 35)
>  		dram_info->ecc_impacting_de_bw =
> REG_FIELD_GET(XE3P_ECC_IMPACTING_DE, val);
>  

RE: [v2 2/2] drm/i915/dram: Interpret 0xF populated-channel count as 16

[Shankar, Uma]

> -----Original Message-----
> From: Govindapillai, Vinod <vinod.govindapillai@intel.com>
> Sent: Wednesday, July 15, 2026 6:01 PM
> To: Shankar, Uma <uma.shankar@intel.com>; intel-xe@lists.freedesktop.org;
> intel-gfx@lists.freedesktop.org
> Cc: Kandpal, Suraj <suraj.kandpal@intel.com>
> Subject: Re: [v2 2/2] drm/i915/dram: Interpret 0xF populated-channel count as 16
> 
> Hi Uma,
> 
> On Wed, 2026-07-15 at 16:11 +0530, Uma Shankar wrote:
> > The register MEM_SS_INFO_GLOBAL [Number of populated channels] field
> > definition is updated with an encoding for 16 channels.
> >
> > For 16-channel configuration, program 1111b. A programmed value of
> > 1111b must be interpreted as 16 channels for memory bandwidth
> > calculations.
> >
> > The MEM_SS_INFO_GLOBAL populated-channel field is only 4 bits and
> > cannot encode 16, so on Xe3p the BIOS programs the saturated field
> > value
> > (0xf)
> > to indicate the fully-populated 16-channel config (4 memory
> > controllers x 4 channels). Interpret it as 16 and let the bandwidth
> > math handle the larger channel count.
> >
> > Gate the behaviour through
> > intel_display_wa(INTEL_DISPLAY_WA_16030862157)
> > instead of an open-coded DISPLAY_VER() check.
> >
> > v2: Switched to intel_display_wa.c framework (Suraj)
> >
> > WA: 16030862157
> > Bspec: 69131, 68859
> > Assisted-by: Claude:claude-opus-4-8
> > Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_bw.c   | 20 +++++++++++++++++---
> >  drivers/gpu/drm/i915/display/intel_dram.c | 12 ++++++++++++
> >  2 files changed, 29 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_bw.c
> > b/drivers/gpu/drm/i915/display/intel_bw.c
> > index 41539fdfeac5..aaa0350dca78 100644
> > --- a/drivers/gpu/drm/i915/display/intel_bw.c
> > +++ b/drivers/gpu/drm/i915/display/intel_bw.c
> > @@ -14,6 +14,7 @@
> >  #include "intel_display_regs.h"
> >  #include "intel_display_types.h"
> >  #include "intel_display_utils.h"
> > +#include "intel_display_wa.h"
> >  #include "intel_dram.h"
> >  #include "intel_mchbar.h"
> >  #include "intel_parent.h"
> > @@ -272,7 +273,14 @@ static int icl_get_qgv_points(struct
> > intel_display *display,
> >  		case INTEL_DRAM_LPDDR4:
> >  		case INTEL_DRAM_LPDDR5:
> >  			qi->t_bl = 16;
> > -			qi->max_numchannels = 8;
> > +			/*
> > +			 * Wa_16030862157
> > +			 * Xe3p supports a fully-populated 16-
> > channel LPDDR
> > +			 * config (4 memory controllers x 4
> > channels); earlier
> > +			 * D14+ platforms top out at 8.
> > +			 */
> > +			qi->max_numchannels =
> > +				intel_display_wa(display,
> > INTEL_DISPLAY_WA_16030862157) ? 16 : 8;
> 
> As per the bspec 68859, max channel of 16 v. 8 is based on a specific sku. Do we
> have any further info on that how to variate that?
> 
> But the INTEL_DISPLAY_WA_16030862157 applies to display versions >= 35
> 
> In tgl_get_bw_info(), we have this adjustment to the deinterleave
> 
> 	if (num_channels < qi.max_numchannels && DISPLAY_VER(display)
> >= 12)
> 		qi.deinterleave = max(qi.deinterleave / 2, 1);
> 
> So with the above change we will always end up in this loop and adjust the
> qi.deinterleave for all versions >= 35 not just the specific "sku"
> which I think is not correct. May be need to check from the IP team or
> clarify/update the bspec?

This is extended for all NVL SKU's, hence the check. However will drop > so that
its restricted only for NVL.

> And another suggestion for your consideration is:
> 
> I didnt find this 1603862157 as part of wa database. Is there any wa bspec? So do
> we need to  implement this as a wa?

This is the WA lineage number which XE driver and bspec follows, hence used the same
here.

> If this is considered as a wa:
> 
> If I understand this correctly, wa is mainly about part where bios populate the
> MTL_N_OF_POPULATED_CH_MASK fields as 0xf in cased of channels 16 and
> we interpret that as channels = 16 instead of 15.
> 
> IMO, ideally it is better to split this into two parts,
> 
> 1. wa definitions in the existing driver wa framework + changes in
> xelpdp_get_dram_info() related to this wa as a single patch like other wa
> implementations in the driver so far.
> 
> 2. Update the bw info changes to add support for max_number of channels to 16 in
> case of a specific SKU and the update to the c9_clperchperblock calculation part.

Sure, sounds good. I will change accordingly.

Regards,
Uma Shankar

> BR
> Vinod
> 
> 
> >  			qi->channel_width = 16;
> >  			qi->deinterleave = 4;
> >  			break;
> > @@ -624,10 +632,16 @@ static int tgl_get_bw_info(struct intel_display
> > *display,
> >
> >  	ipqdepth = min(ipqdepthpch, display_bw_params->displayrtids /
> > num_channels);
> >  	/*
> > +	 * Wa_16030862157
> >  	 * clperchgroup = 4kpagespermempage * clperchperblock,
> > -	 * clperchperblock = 8 / num_channels * interleave
> > +	 * clperchperblock = max(8 / num_channels, 1) * interleave
> > +	 *
> > +	 * The 8 / num_channels truncating divide collapses to 0 for
> > +	 * >8-channel configs (16-channel: 8 / 16 = 0); the max(...,
> > 1) floor
> > +	 * keeps clperchperblock >= 1 there while preserving the
> > literal
> > +	 * truncating divide for <=8-channel configs.
> >  	 */
> > -	clperchgroup = 4 * (8 / num_channels) * qi.deinterleave;
> > +	clperchgroup = 4 * max(8 / num_channels, 1) *
> > qi.deinterleave;
> >
> >  	display->bw.num_qgv_points = qi.num_qgv_points;
> >  	display->bw.num_psf_gv_points = qi.num_psf_points; diff --git
> > a/drivers/gpu/drm/i915/display/intel_dram.c
> > b/drivers/gpu/drm/i915/display/intel_dram.c
> > index f103f7cba018..7e2fc24e240c 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dram.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dram.c
> > @@ -13,6 +13,7 @@
> >  #include "intel_display_core.h"
> >  #include "intel_display_utils.h"
> >  #include "intel_display_regs.h"
> > +#include "intel_display_wa.h"
> >  #include "intel_dram.h"
> >  #include "intel_mchbar.h"
> >  #include "intel_parent.h"
> > @@ -796,6 +797,17 @@ static int xelpdp_get_dram_info(struct
> > intel_display *display, struct dram_info
> >  	dram_info->num_qgv_points =
> > REG_FIELD_GET(MTL_N_OF_ENABLED_QGV_POINTS_MASK, val);
> >  	/* PSF GV points not supported in D14+ */
> >
> > +	/*
> > +	 * Wa_16030862157
> > +	 * MEM_SS_INFO_GLOBAL populated-channel field is only 4 bits
> > and
> > +	 * cannot encode 16, so on Xe3p the BIOS programs the
> > saturated field
> > +	 * value (0xf) to indicate the fully-populated 16-channel
> > config (4
> > +	 * memory controllers x 4 channels). Interpret it as 16.
> > +	 */
> > +	if (intel_display_wa(display, INTEL_DISPLAY_WA_16030862157)
> > &&
> > +	    dram_info->num_channels ==
> > REG_FIELD_MAX(MTL_N_OF_POPULATED_CH_MASK))
> > +		dram_info->num_channels = 16;
> > +
> >  	if (DISPLAY_VER(display) >= 35)
> >  		dram_info->ecc_impacting_de_bw =
> > REG_FIELD_GET(XE3P_ECC_IMPACTING_DE, val);
> >

RE: [v2 0/2] drm/i915/display: Implement Display Wa_16030862157

[Shankar, Uma]

> -----Original Message-----
> From: Shankar, Uma <uma.shankar@intel.com>
> Sent: Wednesday, July 15, 2026 4:11 PM
> To: intel-gfx@lists.freedesktop.org; intel-xe@lists.freedesktop.org
> Cc: Govindapillai, Vinod <vinod.govindapillai@intel.com>; Kandpal, Suraj
> <suraj.kandpal@intel.com>; Shankar, Uma <uma.shankar@intel.com>
> Subject: [v2 0/2] drm/i915/display: Implement Display Wa_16030862157
> 
> Interpret 0xF populated-channel count as 16. For 16-channel configuration, BIOS
> programs 1111b. A programmed value of 1111b must be interpreted as 16
> channels for memory bandwidth calculations.
> This series implements the workaround in driver.

Pushed to drm-intel-next. Thanks for the reviews.

> Uma Shankar (2):
>   drm/i915/display: Add Wa_16030862157 to the display workaround list
>   drm/i915/dram: Interpret 0xF populated-channel count as 16
> 
>  drivers/gpu/drm/i915/display/intel_bw.c       | 20 ++++++++++++++++---
>  .../gpu/drm/i915/display/intel_display_wa.c   |  2 ++
>  .../gpu/drm/i915/display/intel_display_wa.h   |  1 +
>  drivers/gpu/drm/i915/display/intel_dram.c     | 12 +++++++++++
>  4 files changed, 32 insertions(+), 3 deletions(-)
> 
> --
> 2.50.1