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Mon, 19 Oct 2026 01:31:36 -0700 (PDT) From: Mehmet Fide To: Ping-Ke Shih Cc: Bitterblue Smith , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, mehmet.fide@screeningeagle.com Subject: Re: [PATCH rtw-next v6 2/2] wifi: rtw88: support channel switch in AP mode Date: Mon, 19 Oct 2026 10:31:35 +0200 Message-ID: <20261019083135.3251458-1-mehmet.fide@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-wireless@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Ping-Ke, On 2026-10-19, Ping-Ke Shih wrote: > If you download beacon to firmware twice within a period of beacon_int, > a countdown in the air will not present, no? Like this [...] > The 4 is missing. Yes, when a download runs late past the next TBTT. The absolute due time keeps the pace, one download per beacon interval on average, so the AP switches when its stations expect it; v5 queued relative to the previous download and drifted 10 ms per beacon on USB. The price of a download that late is one stale beacon and one count never sent. A station takes its switch time from the counts it sees; at worst one whose first count is the stale one switches one interval late. Forced on an RTL8821CU with a 90 ms delay on every second download: a sniffer saw 9, 8, 8, 6, 4, 4, 2, 2 for count 10, the AP finished on time, and a Windows station followed ten such switches (counts 10 and 50) without a re-association. Without the delay it happened once in nine switches. If you would rather not have it: timing the downloads from the TSF, 10 ms after each TBTT, leaves nearly a whole interval before a beacon goes out without the download. I tried that briefly on the 8821CU; with a 60 ms delay every count stays on the air. Which do you prefer? Thanks, Mehmet