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From: Thomas Monjalon <thomas@monjalon.net>
To: Slava Ovsiienko <viacheslavo@mellanox.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, Matan Azrad <matan@mellanox.com>,
 Raslan Darawsheh <rasland@mellanox.com>
Date: Fri, 17 Jul 2020 17:19:17 +0200
Message-ID: <24924170.TV8gEDprjA@thomas>
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Subject: Re: [dpdk-dev] [PATCH 3/3] common/mlx5: fix DevX register access
	opcode
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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.