RE: [PATCH v5 4/6] wifi: rtw88: sdio: track free TX pages and OQT credits for RTL8723BS

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

luka.gejak@linux.dev <luka.gejak@linux.dev> wrote:
> From: Luka Gejak <luka.gejak@linux.dev>
> 
> The RTL8723BS reports free TX page counts that the generic 8051 path
> reads back from the chip on every transfer, which is both slow over SDIO
> and unreliable on this part: the register frequently reads back zero
> while pages are in fact available. It also gates transmission on a free
> count in the SDIO output queue, REG_SDIO_OQT_FREE_PG, which rtw88 does
> not track at all. The vendor driver calls this the OQT free space and
> never expands the acronym; the register holds the number of further
> transfers the SDIO output queue can accept, and the chip discards
> writes that arrive when it has run out.
> 
> Mirror the vendor driver and keep the per-queue and public page counts
> in software, seeded at start and resynchronised from the chip only when
> the cached counts say there is not enough room. Wait for a free output
> queue entry before writing, and account for the pages consumed after a
> successful transfer.
> 
> Transfers also have to be padded up to the SDIO block size for this
> chip rather than using the generic alignment, so size the write
> separately from the frame and trim the skb back afterwards.
> 
> Measured on RTL8723BS hardware against an iperf3 server one hop behind
> the AP, with the wlan0 byte counters as ground truth. On the generic
> path the association completes but no data passes at all: TCP and UDP
> both measure 0 bit/s in either direction. With this patch TCP is
> 25.3 Mbit/s up and 37.3 Mbit/s down, and UDP is 25.0 Mbit/s up at 0%
> loss.
> 
> Signed-off-by: Luka Gejak <luka.gejak@linux.dev>

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