Re: [PATCH v2 4/4] drm/amd/pm: smu_v14_0_0: add closest-match fallback for DPM level marking

["Lazar, Lijo" <lijo.lazar@amd.com>]

On 10-Jun-26 11:53 PM, Priya Hosur wrote:
> Replace the simple exact-match loop in emit_clk_levels with a
> two-pass approach: the first pass checks whether the current
> frequency matches any DPM level exactly and also tracks the closest
> level by absolute frequency difference. The second pass emits the
> levels, marking the exact match if found, otherwise the closest
> level.
> 
> The SMU reports time-filtered average frequencies that often do not
> match any DPM table entry exactly. Without this fallback, MCLK,
> FCLK and other clocks show DPM levels but never display the *
> marker, breaking userspace tools that rely on it to identify the
> active frequency.
> 
> Also uses reverse DPM index for SMU_MCLK since MemPstateTable
> stores levels high-to-low.
> 
> Signed-off-by: Priya Hosur <Priya.Hosur@amd.com>
> ---
>   .../drm/amd/pm/swsmu/smu14/smu_v14_0_0_ppt.c  | 53 ++++++++++++++++---
>   1 file changed, 46 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0_0_ppt.c b/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0_0_ppt.c
> index 1be8d1a8da19..c01c71acbe3f 100644
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0_0_ppt.c
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0_0_ppt.c
> @@ -1190,14 +1190,53 @@ static int smu_v14_0_0_emit_clk_levels(struct smu_context *smu,
>   		if (ret)
>   			return ret;
>   
> -		for (i = 0; i < count; i++) {
> -			idx = (clk_type == SMU_MCLK) ? (count - i - 1) : i;
> -			ret = smu_v14_0_common_get_dpm_freq_by_index(smu, clk_type, idx, &value);
> -			if (ret)
> -				return ret;
> +		/*
> +		 * Try exact match first. If the SMU reports a time-averaged
> +		 * frequency that doesn't match any DPM level exactly, fall
> +		 * back to marking the closest DPM level.
> +		 */
> +		{
> +			int closest_idx = 0;
> +			uint32_t closest_diff = U32_MAX;
> +			uint32_t diff;
> +			bool exact_match = false;
> +
> +			for (i = 0; i < count; i++) {
> +				idx = (clk_type == SMU_MCLK) ? (count - i - 1) : i;
> +				ret = smu_v14_0_common_get_dpm_freq_by_index(smu, clk_type, idx, &value);
> +				if (ret)
> +					return ret;
> +
> +				if (cur_value == value) {
> +					closest_idx = i;
> +					exact_match = true;
> +					break;
> +				}
> +
> +				diff = abs((int)cur_value - (int)value);
> +				if (diff < closest_diff) {
> +					closest_diff = diff;
> +					closest_idx = i;
> +				} else if (diff > closest_diff) {
> +					break;
> +				}
> +			}
>   
> -			size += sysfs_emit_at(buf, size, "%d: %uMhz %s\n", i, value,
> -					      cur_value == value ? "*" : "");
> +			for (i = 0; i < count; i++) {
> +				idx = (clk_type == SMU_MCLK) ? (count - i - 1) : i;
> +				ret = smu_v14_0_common_get_dpm_freq_by_index(smu, clk_type, idx, &value);
> +				if (ret)
> +					return ret;
> +
> +				if (exact_match)

exact_match is redundant now. It only needs closest_idx check.

Thanks,
Lijo

> +					size += sysfs_emit_at(buf, size, "%d: %uMhz %s\n",
> +							      i, value,
> +							      cur_value == value ? "*" : "");
> +				else
> +					size += sysfs_emit_at(buf, size, "%d: %uMhz %s\n",
> +							      i, value,
> +							      i == closest_idx ? "*" : "");
> +			}
>   		}
>   		break;
>   	case SMU_DCEFCLK: