RE: [Enable Designware XGMAC VLAN Stripping Feature 2/2] net: stmmac: dwxgmac2: Add support for HW-accelerated VLAN Stripping

-----Original Message-----
From: Florian Fainelli <f.fainelli@gmail.com>
Sent: Friday, July 21, 2023 11:59 PM
To: Ng, Boon Khai <redacted>; Krzysztof Kozlowski
[off-list ref]; Boon@ecsmtp.png.intel.com; Khai@ecsmtp.png.intel.com;
Ng, Boon Khai [off-list ref]; Giuseppe Cavallaro
[off-list ref]; Alexandre Torgue [off-list ref];
Jose Abreu [off-list ref]; David S . Miller [off-list ref];
Eric Dumazet [off-list ref]; Jakub Kicinski [off-list ref];
Paolo Abeni [off-list ref]; Maxime Coquelin
[off-list ref]; netdev@vger.kernel.org; linux-stm32@st-md-
mailman.stormreply.com; linux-arm-kernel@lists.infradead.org; linux-
kernel@vger.kernel.org
Cc: Shevchenko, Andriy <redacted>; Tham, Mun Yew
[off-list ref]; Swee, Leong Ching
[off-list ref]; G Thomas, Rohan
[off-list ref]; Shevchenko Andriy
[off-list ref]
Subject: Re: [Enable Designware XGMAC VLAN Stripping Feature 2/2] net:
stmmac: dwxgmac2: Add support for HW-accelerated VLAN Stripping



On 7/21/2023 8:30 AM, Ng, Boon Khai wrote:

quoted

quoted

-----Original Message-----
From: Krzysztof Kozlowski <krzk@kernel.org>
Sent: Friday, July 21, 2023 6:11 PM
To: Boon@ecsmtp.png.intel.com; Khai@ecsmtp.png.intel.com; "Ng
<boon.khai.ng"@intel.com; Giuseppe Cavallaro
[off-list ref]; Alexandre Torgue
[off-list ref]; Jose Abreu [off-list ref];
David S . Miller [off-list ref]; Eric Dumazet
[off-list ref]; Jakub Kicinski [off-list ref]; Paolo Abeni
[off-list ref]; Maxime Coquelin [off-list ref];
netdev@vger.kernel.org; linux-stm32@st- md-mailman.stormreply.com;
linux-arm-kernel@lists.infradead.org; linux- kernel@vger.kernel.org
Cc: Ng, Boon Khai <redacted>; Shevchenko, Andriy
[off-list ref]; Tham, Mun Yew
[off-list ref]; Swee, Leong Ching
[off-list ref]; G Thomas, Rohan
[off-list ref]; Shevchenko Andriy
[off-list ref]
Subject: Re: [Enable Designware XGMAC VLAN Stripping Feature 2/2] net:
stmmac: dwxgmac2: Add support for HW-accelerated VLAN Stripping

On 21/07/2023 08:26, Boon@ecsmtp.png.intel.com wrote:

quoted

From: Boon Khai Ng <redacted>

Currently, VLAN tag stripping is done by software driver in
stmmac_rx_vlan(). This patch is to Add support for VLAN tag
stripping by the MAC hardware and MAC drivers to support it.
This is done by adding rx_hw_vlan() and set_hw_vlan_mode() callbacks
at stmmac_ops struct which are called from upper software layer.

...

quoted

  	if (priv->dma_cap.vlhash) {
  		ndev->features |= NETIF_F_HW_VLAN_CTAG_FILTER;
  		ndev->features |= NETIF_F_HW_VLAN_STAG_FILTER; diff --

git

quoted

a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
index 23d53ea04b24..bd7f3326a44c 100644

--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c

@@ -543,6 +543,12 @@ stmmac_probe_config_dt(struct platform_device

*pdev, u8 *mac)

quoted

  			plat->flags |= STMMAC_FLAG_TSO_EN;
  	}

+	/* Rx VLAN HW Stripping */
+	if (of_property_read_bool(np, "snps,rx-vlan-offload")) {
+		dev_info(&pdev->dev, "RX VLAN HW Stripping\n");

Why? Drop.

This is an dts option export to dts for user to choose whether or not
they Want a Hardware stripping or a software stripping.

May I know what is the reason to drop this?

Because the networking stack already exposes knobs for drivers to advertise and
control VLAN stripping/insertion on RX/TX using ethtool and feature bits
(NETIF_F_HW_VLAN_CTAG_RX, NETIF_F_HW_VLAN_CTAG_TX).

Hi Florian,

Understood, but how does user choose to have the default option
either hardware strip or software strip, when the device just boot up?

I don’t think ethool can "remember" the setting once the device get rebooted?
Any other suggestion of doing it other than using the dts method?

What you are doing here is encode a policy as a Device Tree property rather
than describe whether the hardware supports a given feature and this is frowned
upon.
--
Florian

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