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From:   Heiko =?ISO-8859-1?Q?St=FCbner?= <heiko@sntech.de>
To:     Robin Murphy <robin.murphy@arm.com>
Cc:     "Leonidas P. Papadakos" <papadakospan@gmail.com>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@st.com>,
        netdev@vger.kernel.org, Jose Abreu <joabreu@synopsys.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        klaus.goger@theobroma-systems.com,
        philipp.tomsich@theobroma-systems.com
Subject: Re: [PATCH 1/2] stmmac: introduce flag to dynamically disable TX offload for rockchip devices
Date:   Mon, 01 Apr 2019 21:06:53 +0200
Message-ID: <2312344.mOsv7YkeBG@diego>
In-Reply-To: <9d65a22a-2288-dc53-0059-ec4a31424dd8@arm.com>
References: <20190401181840.31255-1-papadakospan@gmail.com> <9d65a22a-2288-dc53-0059-ec4a31424dd8@arm.com>
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Am Montag, 1. April 2019, 20:54:45 CEST schrieb Robin Murphy:
> On 01/04/2019 19:18, Leonidas P. Papadakos wrote:
> > From: =?UTF-8?q?Kamil=20Trzci=C5=84ski?= <ayufan@ayufan.eu>
> > 
> > Some rockchip boards exhibit an issue where tx checksumming does not work with
> > packets larger than 1498.
> 
> Is it really a board-level problem? I'm no networking expert, but the 
> nature of the workaround suggests this is more likely to be some 
> inherent limitation of the IP block in the SoC, rather than something to 
> do with how the external pins get wired up. Does anyone have an RK3328 
> or RK3399 board that provably *does* checksum large packets correctly?

I don't have that many rk3399-boards with actual ethernet and even only
the rock64 from rk3328-land, but at least my rk3399-firefly also seems
affected by this.

But so far the rk3399-puma board from Theobroma did not show that ethernet
issue for me, so I've added two Theobroma people who may or may not tell
if they've also seen that issue.

> 
> > This is bad for network stability.
> > 
> > The previous approach was using force_thresh_dma_mode in the board dts, which
> > does more than we need.
> 
> If indeed it is a SoC-level thing (or at least we want to treat it as 
> such), then couldn't we just hang it off the existing SoC-specific 
> compatibles in dwmac-rk.c and avoid the need for a new DT property at 
> all? After all, that's precisely why SoC-specific compatibles are a 
> thing in the first place.
> 
> Robin.
> 
> > Signed-off-by: Leonidas P. Papadakos <papadakospan@gmail.com>
> > ---
> >   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c     | 4 ++++
> >   drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 2 ++
> >   include/linux/stmmac.h                                | 1 +
> >   3 files changed, 7 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 6a2e1031a..4552147e9 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -3660,6 +3660,10 @@ static netdev_features_t stmmac_fix_features(struct net_device *dev,
> >   	if (priv->plat->bugged_jumbo && (dev->mtu > ETH_DATA_LEN))
> >   		features &= ~NETIF_F_CSUM_MASK;
> >   
> > +	/* Including very small MTUs of 1498 for Rockchip devices */
> > +	if (priv->plat->bugged_tx_coe && (dev->mtu > ETH_DATA_LEN - 2))
> > +		features &= ~NETIF_F_CSUM_MASK;
> > +
> >   	/* Disable tso if asked by ethtool */
> >   	if ((priv->plat->tso_en) && (priv->dma_cap.tsoen)) {
> >   		if (features & NETIF_F_TSO)
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> > index 3031f2bf1..807cf5826 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> > @@ -519,6 +519,8 @@ stmmac_probe_config_dt(struct platform_device *pdev, const char **mac)
> >   		pr_warn("force_sf_dma_mode is ignored if force_thresh_dma_mode is set.");
> >   	}
> >   
> > +	plat->bugged_tx_coe = of_property_read_bool(np, "rockchip,bugged_tx_coe");
> > +
> >   	of_property_read_u32(np, "snps,ps-speed", &plat->mac_port_sel_speed);
> >   
> >   	plat->axi = stmmac_axi_setup(pdev);
> > diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> > index 4335bd771..60c411f43 100644
> > --- a/include/linux/stmmac.h
> > +++ b/include/linux/stmmac.h
> > @@ -162,6 +162,7 @@ struct plat_stmmacenet_data {
> >   	int pmt;
> >   	int force_sf_dma_mode;
> >   	int force_thresh_dma_mode;
> > +	int bugged_tx_coe;
> >   	int riwt_off;
> >   	int max_speed;
> >   	int maxmtu;
> > 
>