Messages in this thread |  | | Date | Tue, 04 Feb 2020 10:37:49 +0100 (CET) | Subject | Re: [PATCH v2 2/2] net: macb: Limit maximum GEM TX length in TSO | From | David Miller <> |
| |
From: Harini Katakam <harini.katakam@xilinx.com> Date: Mon, 3 Feb 2020 18:48:02 +0530
> GEM_MAX_TX_LEN currently resolves to 0x3FF8 for any IP version supporting > TSO with full 14bits of length field in payload descriptor. But an IP > errata causes false amba_error (bit 6 of ISR) when length in payload > descriptors is specified above 16387. The error occurs because the DMA > falsely concludes that there is not enough space in SRAM for incoming > payload. These errors were observed continuously under stress of large > packets using iperf on a version where SRAM was 16K for each queue. This > errata will be documented shortly and affects all versions since TSO > functionality was added. Hence limit the max length to 0x3FC0 (rounded). > > Signed-off-by: Harini Katakam <harini.katakam@xilinx.com> > --- > v2: > Use 0x3FC0 by default
You should add a comment above the definition which explains how this value was derived. It looks magic currently.
|  |