Date:   Thu, 9 Mar 2023 13:13:58 +0100
From:   Sascha Hauer <s.hauer@pengutronix.de>
To:     Ping-Ke Shih <pkshih@realtek.com>
Cc:     Larry Finger <Larry.Finger@lwfinger.net>,
        linux-wireless <linux-wireless@vger.kernel.org>
Subject: Re: Performance of rtw88_8822bu
Message-ID: <20230309121358.GG5784@pengutronix.de>
References: <93d565e1-3a23-69f3-bedd-b71eb601bceb@lwfinger.net>
 <20230306091845.GC27249@pengutronix.de>
 <20230306125944.GD27249@pengutronix.de>
 <6ed1239f8c404dcb9d571771c230b69b@realtek.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <6ed1239f8c404dcb9d571771c230b69b@realtek.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Precedence: bulk

On Tue, Mar 07, 2023 at 01:39:19AM +0000, Ping-Ke Shih wrote:
> 
> 
> > -----Original Message-----
> > From: Sascha Hauer <s.hauer@pengutronix.de>
> > Sent: Monday, March 6, 2023 9:00 PM
> > To: Larry Finger <Larry.Finger@lwfinger.net>
> > Cc: Ping-Ke Shih <pkshih@realtek.com>; linux-wireless <linux-wireless@vger.kernel.org>
> > Subject: Re: Performance of rtw88_8822bu
> > 
> > On Mon, Mar 06, 2023 at 10:18:45AM +0100, Sascha Hauer wrote:
> > > Hi Larry,
> > >
> > > On Sat, Mar 04, 2023 at 08:52:26PM -0600, Larry Finger wrote:
> > > > Sascha an Ping-Ke,
> > > >
> > > > I have been testing the RTW8822BU driver found in my rtw88 GitHub repo. This
> > > > code matches the code found in wireless-next. I created 9 files of 5.8 GiB
> > > > each and used a for loop to copy them from the test computer to/from my
> > > > server. The wireless connection is on the 5 GHz band (channel 153) connected
> > > > to an ax1500 Wifi 6 router, which in turn is connected to the server via a
> > > > 1G ethernet cable. The connection has not crashed, but I see strange
> > > > behavior.
> > >
> > > What chipset are you using? Is it a RTL8822bu or some other chipset
> > > reported by the driver?
> > >
> > > >
> > > > With both TX and RX, the rate is high at 13.5 MiB/s for RX and 11.1 MiB/s
> > > > for TX for about 1/3 of the time, but then the driver reports "timed out to
> > > > flush queue 3" and the rate drops to 3-5 MiB/s for RX and 2-3 MiB/s for TX.
> > > > These low rates are in effect for 2/3 of the time. The 5G bands are
> > > > relatively unused in my house, thus I do not suspect interference.
> > >
> > > I've received a very similar report this weekend. About 3-4 messages per
> > > second, "timed out to flush queue 3", but driver continues to work.
> > > I've also seen it this morning by accident and once again while writing
> > > this mail. This was on a RTL8821CU.
> > >
> > > So far I have no idea what the problem might be.
> > 
> > The "timed out to flush queue %d\n" message comes from
> > __rtw_mac_flush_prio_queue(). Here some registers are read which show
> > the number of reserved pages for a queue and the number of available
> > pages of a queue. I used the debugfs interface to observe these
> > registers from time to time:
> > 
> > f=$(echo /sys/kernel/debug/ieee80211/phy*/rtw88/read_reg); for i in 0x230 0x234 0x238 0x23c; do echo "$i
> > 4" > $f; cat $f; done
> > 
> > This is what they show:
> > 
> > reg 0x230: 0x00230040
> > reg 0x234: 0x00400040
> > reg 0x238: 0x00400040
> > reg 0x23c: 0x00000000
> > 
> > The upper 16bit contain the number of available pages and the lower
> > 16bit contain the number of reserved pages (Note these are the registers
> > on a RTL8822CU, on other chipsets the number of available pages is
> > lower, like 0x10 on RTL8821CU). Register 0x230 is the interesting one
> > for us, it has the values for queue 3.
> > 
> > What I can see is that for the other queues the number of reserved pages
> > usually matches the number of available pages. It happens sometimes that
> > the number of available pages goes down to 0x3f, but with the next
> > register read it goes back to 0x40. For 0x230 this is different though.
> > Here the number of available pages continuously decreases over time and
> > never goes back up.
> > 
> > I don't know what this is trying to tell me. It seems that things queued
> > to queue RTW_DMA_MAPPING_HIGH are sometimes (always?) stuck.
> > Unfortunately I also don't know how the different priority queues relate
> > to the different USB endpoints and how these in turn go together with
> > the qsel settings. Maybe Ping-Ke can shed some light on this.
> > 
> 
> To quickly check if RTW_DMA_MAPPING_HIGH get stuck, changing qsel_to_ep[]
> to different priority queue would be helpful to identify the problem.
> If only this queue works not well, we may dig MAC settings. Otherwise,
> it may be a RF performance problem.

By changing qsel_to_ep[] I can shift the problem to other priority
queues.

I changed qsel_to_ep[] back to default then and tried this instead:

-       txdma_pq_map |= BIT_TXDMA_HIQ_MAP(rqpn->dma_map_hi);
-       txdma_pq_map |= BIT_TXDMA_MGQ_MAP(rqpn->dma_map_mg);
+       txdma_pq_map |= BIT_TXDMA_HIQ_MAP(RTW_DMA_MAPPING_NORMAL);
+       txdma_pq_map |= BIT_TXDMA_MGQ_MAP(RTW_DMA_MAPPING_NORMAL);

From my understanding RTW_DMA_MAPPING_HIGH shouldn't be used anymore and
I assumed that the number of available pages shown at 0x230
(REG_FIFOPAGE_INFO_1) shouldn't shrink anymore. To my surprise the value
in 0x230 is still shrinking.

I still wonder how the different endpoints relate to the different
priority queues. Does a packet destined for a certain priority queue
have to go through a specific endpoint, or are they completly unrelated?

Sascha

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |