RE: [PATCH rtw] wifi: rtw89: hw_scan: Don't let the operating channel be last

[Ping-Ke Shih <pkshih@realtek.com>]

Bitterblue Smith <rtl8821cerfe2@gmail.com> wrote:
> Scanning can be offloaded to the firmware. To that end, the driver
> prepares a list of channels to scan, including periodic visits back to
> the operating channel, and sends the list to the firmware.
> 
> When the channel list is too long to fit in a single H2C message, the
> driver splits the list, sends the first part, and tells the firmware to
> scan. When the scan is complete, the driver sends the next part of the
> list and tells the firmware to scan.
> 
> When the last channel that fit in the H2C message is the operating
> channel something seems to go wrong in the firmware. It will
> acknowledge receiving the list of channels but apparently it will not
> do anything more. The AP can't be pinged anymore. The driver still
> receives beacons, though.
> 
> One way to avoid this is to split the list of channels before the
> operating channel.
> 
> Affected devices:
> 
> * RTL8851BU with firmware 0.29.41.3
> * RTL8832BU with firmware 0.29.29.8
> * RTL8852BU with firmware 0.29.29.8

We don't see this problem with the same firmware on RTL8852BE and RTL8852CE,
and I'd spend some time to check if this impact scan time. Or could you share?

Otherwise, it looks good to me, so give my ACK in advance

Acked-by: Ping-Ke Shih <pkshih@realtek.com>


> 
> https://lore.kernel.org/linux-wireless/0abbda91-c5c2-4007-84c8-215679e652e1@gmail.com/
> Cc: stable@vger.kernel.org
> Signed-off-by: Bitterblue Smith <rtl8821cerfe2@gmail.com>
> ---
> I didn't think a workaround would be needed in the kernel but 6.18
> will be out soon and people still have this problem.
> ---
>  drivers/net/wireless/realtek/rtw89/fw.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/net/wireless/realtek/rtw89/fw.c b/drivers/net/wireless/realtek/rtw89/fw.c
> index 96f0463e66d6..c35317abc7f5 100644
> --- a/drivers/net/wireless/realtek/rtw89/fw.c
> +++ b/drivers/net/wireless/realtek/rtw89/fw.c
> @@ -7709,6 +7709,13 @@ int rtw89_hw_scan_add_chan_list_ax(struct rtw89_dev *rtwdev,
>         INIT_LIST_HEAD(&list);
> 
>         list_for_each_entry_safe(ch_info, tmp, &scan_info->chan_list, list) {
> +               /* The operating channel (tx_null == true) should
> +                * not be last in the list, to avoid breaking
> +                * RTL8851BU and RTL8832BU.
> +                */
> +               if (list_len + 1 == RTW89_SCAN_LIST_LIMIT_AX && ch_info->tx_null)
> +                       break;
> +
>                 list_move_tail(&ch_info->list, &list);
> 
>                 list_len++;
> --
> 2.51.1