Re: [Intel-gfx] [PATCH v2] drm/i915: Remove memory frequency calculation

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Oct 12, 2021 at 06:00:46PM -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.

I don't think the alternate ref clock was ever used.
At least I don't recall ever seeing it.

The real problem with this is that IIRC this is just the last
requested frequency. So on a system with SAGV this will
change dynamically.

> 
> So here dropping it as whole.

We have a second copy of this in gen6_update_ring_freq(). Rather
than removing one and leaving another potentially broken one behind we
should probably just consolidate on a single implementation.

> 
> v2:
> - Also remove memory frequency calculation for gen9 LP platforms
> 
> Cc: Yakui Zhao <yakui.zhao@intel.com>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Fixes: f8112cb9574b ("drm/i915/gen11+: Only load DRAM information from pcode")
> Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h   |  8 --------
>  drivers/gpu/drm/i915/intel_dram.c | 30 ++----------------------------
>  2 files changed, 2 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index a897f4abea0c3..8825f7ac477b6 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -11109,12 +11109,6 @@ enum skl_power_gate {
>  #define  DC_STATE_DEBUG_MASK_CORES	(1 << 0)
>  #define  DC_STATE_DEBUG_MASK_MEMORY_UP	(1 << 1)
>  
> -#define BXT_P_CR_MC_BIOS_REQ_0_0_0	_MMIO(MCHBAR_MIRROR_BASE_SNB + 0x7114)
> -#define  BXT_REQ_DATA_MASK			0x3F
> -#define  BXT_DRAM_CHANNEL_ACTIVE_SHIFT		12
> -#define  BXT_DRAM_CHANNEL_ACTIVE_MASK		(0xF << 12)
> -#define  BXT_MEMORY_FREQ_MULTIPLIER_HZ		133333333
> -
>  #define BXT_D_CR_DRP0_DUNIT8			0x1000
>  #define BXT_D_CR_DRP0_DUNIT9			0x1200
>  #define  BXT_D_CR_DRP0_DUNIT_START		8
> @@ -11145,9 +11139,7 @@ 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..0adadfd9528aa 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;
>  }
>  
> @@ -350,24 +338,10 @@ static void bxt_get_dimm_info(struct dram_dimm_info *dimm, u32 val)
>  static int bxt_get_dram_info(struct drm_i915_private *i915)
>  {
>  	struct dram_info *dram_info = &i915->dram_info;
> -	u32 dram_channels;
> -	u32 mem_freq_khz, val;
> -	u8 num_active_channels, valid_ranks = 0;
> +	u32 val;
> +	u8 valid_ranks = 0;
>  	int i;
>  
> -	val = intel_uncore_read(&i915->uncore, BXT_P_CR_MC_BIOS_REQ_0_0_0);
> -	mem_freq_khz = DIV_ROUND_UP((val & BXT_REQ_DATA_MASK) *
> -				    BXT_MEMORY_FREQ_MULTIPLIER_HZ, 1000);
> -
> -	dram_channels = val & BXT_DRAM_CHANNEL_ACTIVE_MASK;
> -	num_active_channels = hweight32(dram_channels);
> -
> -	if (mem_freq_khz * num_active_channels == 0) {
> -		drm_info(&i915->drm,
> -			 "Couldn't get system memory bandwidth\n");
> -		return -EINVAL;
> -	}
> -
>  	/*
>  	 * Now read each DUNIT8/9/10/11 to check the rank of each dimms.
>  	 */
> -- 
> 2.33.0

-- 
Ville Syrjälä
Intel