[Intel-gfx] [PATCH] drm/i915: Remove memory frequency calculation

[Matt Roper]

On Tue, Oct 12, 2021 at 05:24:55PM -0700, José Roberto de Souza wrote:
> This memory frequency calculated is only used to check if it is zero,
> what is not useful as it will never actually be zero.
> 
> Also the calculation is wrong, we should be checking other bit to
> select the appropriate frequency multiplier while this code is stuck
> with a fixed multiplier.
> 
> So here dropping it as whole.

I think we can do similar cleanup in bxt_get_dram_info() too.  The value
of BXT_P_CR_MC_BIOS_REQ_0_0_0 that we read is used to obtain
mem_freq_khz and dram_channels/num_active_channels, but none of those
variables are ever used for anything except a needless zero-check.


Matt

> Cc: Yakui Zhao <yakui.zhao at intel.com>
> Cc: Matt Roper <matthew.d.roper at intel.com>
> Fixes: f8112cb9574b ("drm/i915/gen11+: Only load DRAM information from pcode")
> Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h   |  2 --
>  drivers/gpu/drm/i915/intel_dram.c | 12 ------------
>  2 files changed, 14 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index a897f4abea0c3..03b6c505249dc 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -11145,9 +11145,7 @@ enum skl_power_gate {
>  #define  BXT_DRAM_TYPE_LPDDR4			(0x2 << 22)
>  #define  BXT_DRAM_TYPE_DDR4			(0x4 << 22)
>  
> -#define SKL_MEMORY_FREQ_MULTIPLIER_HZ		266666666
>  #define SKL_MC_BIOS_DATA_0_0_0_MCHBAR_PCU	_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5E04)
> -#define  SKL_REQ_DATA_MASK			(0xF << 0)
>  #define  DG1_GEAR_TYPE				REG_BIT(16)
>  
>  #define SKL_MAD_INTER_CHANNEL_0_0_0_MCHBAR_MCMAIN _MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5000)
> diff --git a/drivers/gpu/drm/i915/intel_dram.c b/drivers/gpu/drm/i915/intel_dram.c
> index 30a0cab5eff46..31933b1e7277b 100644
> --- a/drivers/gpu/drm/i915/intel_dram.c
> +++ b/drivers/gpu/drm/i915/intel_dram.c
> @@ -244,7 +244,6 @@ static int
>  skl_get_dram_info(struct drm_i915_private *i915)
>  {
>  	struct dram_info *dram_info = &i915->dram_info;
> -	u32 mem_freq_khz, val;
>  	int ret;
>  
>  	dram_info->type = skl_get_dram_type(i915);
> @@ -255,17 +254,6 @@ skl_get_dram_info(struct drm_i915_private *i915)
>  	if (ret)
>  		return ret;
>  
> -	val = intel_uncore_read(&i915->uncore,
> -				SKL_MC_BIOS_DATA_0_0_0_MCHBAR_PCU);
> -	mem_freq_khz = DIV_ROUND_UP((val & SKL_REQ_DATA_MASK) *
> -				    SKL_MEMORY_FREQ_MULTIPLIER_HZ, 1000);
> -
> -	if (dram_info->num_channels * mem_freq_khz == 0) {
> -		drm_info(&i915->drm,
> -			 "Couldn't get system memory bandwidth\n");
> -		return -EINVAL;
> -	}
> -
>  	return 0;
>  }
>  
> -- 
> 2.33.0
> 

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795