Re: [PATCH v9 6/9] wifi: ath12k: add support for setting fixed HE rate/GI/LTF

Pradeep Kumar Chitrapu <quic_pradeepc@xxxxxxxxxxx> · Tue, 28 Jan 2025 10:44:03 -0800

On 1/24/2025 12:26 AM, Maxime Bizon wrote:

On Thu, 2025-01-23 at 17:09 -0800, Pradeep Kumar Chitrapu wrote:

Hello,

I believe, this is default GI based on device capability of HE for
ath11k or EHT for ath12k.

Your patch alters the behaviour of this code in
ath12k_peer_assoc_h_ht():

         /* As firmware handles these two flags (IEEE80211_HT_CAP_SGI_20
          * and IEEE80211_HT_CAP_SGI_40) for enabling SGI, reset both
          * flags if guard interval is Default GI
          */
	if (arvif->bitrate_mask.control[band].gi == NL80211_TXRATE_DEFAULT_GI)
	        arg->peer_ht_caps &= ~(IEEE80211_HT_CAP_SGI_20 |
				IEEE80211_HT_CAP_SGI_40);

	if (arvif->bitrate_mask.control[band].gi != NL80211_TXRATE_FORCE_LGI) {
		if (ht_cap->cap & (IEEE80211_HT_CAP_SGI_20 |
	            IEEE80211_HT_CAP_SGI_40))
                         arg->peer_rate_caps |= WMI_HOST_RC_SGI_FLAG;
	}

I don't understand why a patch adding a feature to force GI would alter
the current behaviour without any actual forcing ?

Hi Maxime,

Apologize for my earlier comment. Firmware relies on peer_rate_caps and 
bandwidth settings when configuring GI. Currently default is configured 
as FORCE_SGI. When there is fixed rate settings configured from user 
space to override defaults to replace SHORT GI with DEFAULT_GI, the code 
snippet you mentioned ensures honoring this by removing HT_CAP_SGI_20 
and HT_CAP_SGI_40. The behavior has been same for ath11k driver as well.

I will get back with more detailed information as soon as possible.

Thanks for understanding,

Best regards,
Pradeep