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Date: Tue, 9 Sep 2025 17:18:26 +0100
From: Simon Horman <horms@kernel.org>
To: Vivian Wang <wangruikang@iscas.ac.cn>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>, Jakub Kicinski <kuba@kernel.org>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>, Yixun Lan <dlan@gentoo.org>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>, Paolo Abeni <pabeni@redhat.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>, Alexandre Ghiti <alex@ghiti.fr>,
	Vadim Fedorenko <vadim.fedorenko@linux.dev>,
	Junhui Liu <junhui.liu@pigmoral.tech>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-riscv@lists.infradead.org, spacemit@lists.linux.dev,
	linux-kernel@vger.kernel.org,
	Troy Mitchell <troy.mitchell@linux.spacemit.com>,
	Vivian Wang <uwu@dram.page>
Subject: Re: [PATCH net-next v9 2/5] net: spacemit: Add K1 Ethernet MAC
Message-ID: <20250909161826.GA23218@horms.kernel.org>
References: <20250905-net-k1-emac-v9-0-f1649b98a19c@iscas.ac.cn>
 <20250905-net-k1-emac-v9-2-f1649b98a19c@iscas.ac.cn>
 <20250905153500.GH553991@horms.kernel.org>
 <0605f176-5cdb-4f5b-9a6b-afa139c96732@iscas.ac.cn>
 <20250905160158.GI553991@horms.kernel.org>
 <45053235-3b01-42d8-98aa-042681104d11@iscas.ac.cn>
 <20250909161549.GC20205@horms.kernel.org>
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In-Reply-To: <20250909161549.GC20205@horms.kernel.org>

On Tue, Sep 09, 2025 at 05:15:56PM +0100, Simon Horman wrote:
> On Sat, Sep 06, 2025 at 12:35:37AM +0800, Vivian Wang wrote:
> > On 9/6/25 00:01, Simon Horman wrote:
> > 
> > > On Fri, Sep 05, 2025 at 11:45:29PM +0800, Vivian Wang wrote:
> > >
> > > ...
> > >
> > > Hi Vivian,
> > >
> > >>>> +		status = emac_rx_frame_status(priv, rx_desc);
> > >>>> +		if (unlikely(status == RX_FRAME_DISCARD)) {
> > >>>> +			ndev->stats.rx_dropped++;
> > >>> As per the comment in struct net-device,
> > >>> ndev->stats should not be used in modern drivers.
> > >>>
> > >>> Probably you want to implement NETDEV_PCPU_STAT_TSTATS.
> > >>>
> > >>> Sorry for not mentioning this in an earlier review of
> > >>> stats in this driver.
> > >>>
> > >> On a closer look, these counters in ndev->stats seems to be redundant
> > >> with the hardware-tracked statistics, so maybe I should just not bother
> > >> with updating ndev->stats. Does that make sense?
> > > For rx/tx packets/bytes I think that makes sense.
> > > But what about rx/tx drops?
> > 
> > Right... but tstats doesn't have *_dropped. It seems that tx_dropped and
> > rx_dropped are considered "slow path" for real devices. It makes sense
> > to me that those should be very rare.
> > 
> > So it seems that what I should do is to just track tx_dropped and
> > rx_dropped myself in a member in emac_priv and report in the
> > ndo_get_stats64 callback, and use the hardware stuff for the rest, as
> > implemented now.
> 
> Thanks, that makes sense to me.

Oops, for the 2nd time today I see I've responded where other's have
already done so. In this case, please take Jakub's advice elsewhere
in this thread.