Subject: Re: [PATCH net 1/1] net: stmmac: disable Split Header (SPH) for Intel platforms

From: Tan Tee Min <[email-masked]>
Date: Thu, 28 Apr 2022 09:55:38 +0800

On Tue, Apr 26, 2022 at 03:58:56PM +0200, Kurt Kanzenbach wrote:
> Hi,
> 
> On Tue Apr 26 2022, Tan Tee Min wrote:
> > Based on DesignWare Ethernet QoS datasheet, we are seeing the limitation
> > of Split Header (SPH) feature is not supported for Ipv4 fragmented packet.
> > This SPH limitation will cause ping failure when the packets size exceed
> > the MTU size. For example, the issue happens once the basic ping packet
> > size is larger than the configured MTU size and the data is lost inside
> > the fragmented packet, replaced by zeros/corrupted values, and leads to
> > ping fail.
> >
> > So, disable the Split Header for Intel platforms.
> 
> Does this issue only apply on Intel platforms?

According to Synopsys IP support, they have confirmed the header-payload
splitting for IPv4 fragmented packets is not supported for the Synopsys
Ether IPs.

Intel platforms are integrating with GMAC EQoS IP which is impacted by the
limitation above, so we are changing the default SPH setting to disabled
for Intel Platforms only.

If anyone can confirm on their platform also having the same issues,
then we would change the SPH default to disable across the IPs.

Thanks,
Tee Min