Re: [dpdk-dev] [PATCH 3/3] common/mlx5: fix DevX register access opcode

[Thomas Monjalon <thomas@monjalon.net>]

17/07/2020 17:23, Slava Ovsiienko:
> 
> > -----Original Message-----
> > From: Thomas Monjalon <thomas@monjalon.net>
> > Sent: Friday, July 17, 2020 18:19
> > To: Slava Ovsiienko <viacheslavo@mellanox.com>
> > Cc: dev@dpdk.org; Matan Azrad <matan@mellanox.com>; Raslan
> > Darawsheh <rasland@mellanox.com>
> > Subject: Re: [PATCH 3/3] common/mlx5: fix DevX register access opcode
> > 
> > 17/07/2020 17:11, Slava Ovsiienko:
> > > From: Thomas Monjalon <thomas@monjalon.net>
> > > > 17/07/2020 16:28, Viacheslav Ovsiienko:
> > > > > The dedicated MLX5_CMD_OP_ACCESS_REGISTER_USER opcode must
> > be
> > > > used to
> > > > > read hardware register content from unprotected mode.
> > > >
> > > > Otherwise? What was broken?
> > >
> > > Otherwise the MLX5_CMD_OP_ACCESS_REGISTER  was used, it returned
> > > EINVAL and register value was not read. It was supposed to enable
> > > ACCESS_REGISTER operation from user mode in kernel driver to read
> > > registers, but eventually it was replaced with ACCESS_REGISTER_USER
> > dedicated operation.
> > >
> > > mlx5 PMD does not rely on this feature strongly, if register reading
> > > fails it deduces the timestamp mode from reported timestamp counter
> > > frequency.
> > 
> > OK I think some of these explanations deserve to be in the commit log.
> 
>  M-m-m-m, this is quite tiny 2-lines fix, we are going to squash it before rc2 😊
> OK, will add the comment about dedicated opcode.

If the patch is squashed with the root cause, no need to explain indeed.