Re: [v3 2/2] drm/i915/xe3p/bw: Update bw calculation to account for 16 channels

["Govindapillai, Vinod" <vinod.govindapillai@intel.com>]

On Wed, 2026-07-15 at 20:02 +0530, Uma Shankar wrote:
> Wa_16030862157:
> Update Bandwidth Calculation to account for 16channel memory
> config.
> 
> v2: Logical separation of changes (Suraj, Vinod)
> 
> WA: 16030862157, 16030875223
> 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 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 

pls have a look at the patch subject/description format changes
suggested by Suraj Otherwise LGTM

Reviewed-by: Vinod Govindapillai <vinod.govindapillai@intel.com>

> 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;