Jesuiter, Henry <henry.jesuiter@xxxxxxxxxxx> wrote: > > we are using the rtw88 driver (with kernel 5.4) together with a RTL8822ce chip (Firmware 9.9.15, WOW 9.9.4, > H2C Version 15) on a PCI-Express card. We stumbled about long roaming durations and investigated a little > into this issue, by using different hardware: > * Freescale i.MX6/ARMv7 > * Intel Core i5-7300) > > and different distributions: > * Yocto Hardknott/3.3.6, Kernel 5.4 > * Buildroot, Kernel 6.6 > * Ubuntu 20.04, Kernel 5.15 > * Ubuntu 24.04, Kernel 6.8 > > and found roaming times from 450ms (Ubuntu 24.04, Intel) up to 900ms (Yocto 3.3.6, FreeScale). Does it mean 450ms on kernel 5.15, but 900ms on kernel 5.4 for RTL8822ce? > > Since we are used to much shorter roaming times (about 200ms even on the Freescale), What is the WiFi card you are used to measure this roaming time? > 2. Start authentication to the new AP > [ 561.557691] wlan0: authenticate with <new_ssid> > 2.1 Reinitialize the hardware > [ 561.577099] rtw_8822ce 0000:01:00.0: rtw_power_on() > [ 561.577109] rtw_8822ce 0000:01:00.0: rtw_hci_setup() > [ 561.577128] rtw_8822ce 0000:01:00.0: rtw_mac_power_on() > [ 561.577262] rtw_8822ce 0000:01:00.0: rtw_mac_power_switch() > [ 561.580561] rtw_8822ce 0000:01:00.0: rtw_wait_firmware_completion() > [ 561.584826] rtw_8822ce 0000:01:00.0: rtw_download_firmware() > => about 40ms here > [ 561.614635] rtw_8822ce 0000:01:00.0: rtw_hci_setup() > [ 561.614657] rtw_8822ce 0000:01:00.0: rtw_mac_init() > => about 250ms here > [ 561.876080] rtw_8822ce 0000:01:00.0: rtw_hci_start() > ... I measure rtw_leave_ips() which is to power on wifi card, and the cost is about 200ms in my x86 NB. > 2.2 PHY calibration > [ 561.877140] rtw_8822ce 0000:01:00.0: [RFK] WiFi / BT RFK handshake start!! > ... > [ 561.896456] rtw_8822ce 0000:01:00.0: [RFK] WiFi / BT RFK handshake finish!! > [ 561.936393] rtw_8822ce 0000:01:00.0: [DPK] s0 dpk start > [ 562.056272] rtw_8822ce 0000:01:00.0: [DPK] s0 dpk finish > [ 562.056280] rtw_8822ce 0000:01:00.0: [DPK] s1 dpk start > [ 562.176275] rtw_8822ce 0000:01:00.0: [DPK] s1 dpk finish > => about additional 300ms until here (that's the phy calibration stuff) I measure rtw_chip_prepare_tx() which is to do phy calibration. The cost is about 190ms on 2GHz and 5GHz channels. > > So, we are wondering if this long duration times for reassociation are hardware-related (maybe even someone > uses the same chip and does not experience these delays)? > > On the software side, is there some optimization potential known in the software/driver that is just not > realized yet? We would be happy to realize/implement those potentials. To be more specific: We are looking > for a way that the driver does not need to reinitialize/restart the hardware while roaming in order to reduce > that part of the roaming delay specifically (and maybe skip/shorten the phy_calibration part). Any ideas > are welcome. We are also happy to provide any additional logs that might be needed (please specify) and > to answer any additional question you might have. The costs I posted are hardware-related. Ignore IEEE80211_CONF_IDLE to avoid calling rtw_enter_ips()/rtw_leave_ips(), saving 200ms to power on hardware. For PHY calibration, I think this is strictly necessary to get good performance. One way may be deferred the calibration after getting connected, but 4 way and DHCP (right after getting connected) may not work well result from bad RF signal quality.
