linux-kernel - RE: [PATCH net 4/4] dpaa_eth: FMan erratum A050385 workaround

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Date:   Wed, 4 Mar 2020 15:51:09 +0000
From:   "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>
To:     David Miller <davem@...emloft.net>,
        "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Leo Li <leoyang.li@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH net 4/4] dpaa_eth: FMan erratum A050385 workaround

> -----Original Message-----
> From: David Miller <davem@...emloft.net>
> Sent: Wednesday, March 4, 2020 1:54 AM
> To: Madalin Bucur (OSS) <madalin.bucur@....nxp.com>
> Subject: Re: [PATCH net 4/4] dpaa_eth: FMan erratum A050385 workaround
> 
> From: Madalin Bucur <madalin.bucur@....nxp.com>
> Date: Tue,  3 Mar 2020 17:55:39 +0200
> 
> > +#define DPAA_FD_DATA_ALIGNMENT  ((fman_has_errata_a050385()) ? \
> 
> You don't need parenthesis around that fman_has_errata_a050385() call.
> 
> > +#define dpaa_bp_size(raw_size) ((SKB_WITH_OVERHEAD(raw_size)) & \
> 
> Similar again for SKB_WITH_OVERHEAD()

I'll send a v2, thanks.
 
> Also, how often does this errata code trigger on effected platforms and
> what is the performance degradation from that?  I don't see this analysis
> performed anywhere.

To reproduce this issue when the workaround is not applied, one
needs to ensure the FMan DMA transaction queue is already full
when a transaction split occurs so the system must be under high
traffic load (i.e. multiple ports at line rate). After the errata
occurs, the traffic stops. The only SoC impacted by this is the
LS1043A, the other ARM DPAA 1 SoC or the PPC DPAA 1 SoCs do not
have this erratum.

Madalin