linux-kernel - Re: [PATCH 1/2] stmmac: introduce flag to dynamically disable TX offload for rockchip devices

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Message-Id: <9EC67532-2D43-4AAD-BFA7-8B6797067427@theobroma-systems.com>
Date:   Mon, 1 Apr 2019 21:12:21 +0200
From:   Philipp Tomsich <philipp.tomsich@...obroma-systems.com>
To:     Heiko Stübner <heiko@...ech.de>,
        Christoph Müllner 
        <christoph.muellner@...obroma-systems.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        "Leonidas P. Papadakos" <papadakospan@...il.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        netdev@...r.kernel.org, Jose Abreu <joabreu@...opsys.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Klaus Goger <klaus.goger@...obroma-systems.com>
Subject: Re: [PATCH 1/2] stmmac: introduce flag to dynamically disable TX
 offload for rockchip devices

+ Christoph.

> On 01.04.2019, at 21:06, Heiko Stübner <heiko@...ech.de> wrote:
> 
> 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@...fan.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@...il.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;
>>> 
>> 
> 
> 
> 
>