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From: "Marek Behún" <kabel@kernel.org>
To: Holger Brunck <holger.brunck@hitachienergy.com>
Cc: netdev@vger.kernel.org, Andrew Lunn <andrew@lunn.ch>,
	Jakub Kicinski <kuba@kernel.org>
Subject: Re: [v4] dsa: mv88e6xxx: make serdes SGMII/Fiber tx amplitude configurable
Date: Tue, 8 Feb 2022 17:12:19 +0100	[thread overview]
Message-ID: <20220208171219.022165d1@thinkpad> (raw)
In-Reply-To: <20220208094455.28870-1-holger.brunck@hitachienergy.com>

On Tue,  8 Feb 2022 10:44:55 +0100
Holger Brunck <holger.brunck@hitachienergy.com> wrote:

> +static struct mv88e6352_serdes_p2p_to_val mv88e6352_serdes_p2p_to_val[] = {
> +	/* Mapping of configurable mikrovolt values to the register value */
> +	{ 14000, 0},
> +	{ 112000, 1},
> +	{ 210000, 2},
> +	{ 308000, 3},
> +	{ 406000, 4},
> +	{ 504000, 5},
> +	{ 602000, 6},
> +	{ 700000, 7},
> +};

...

> +	reg = (reg & MV88E6352_SERDES_OUT_AMP_MASK) | val;

This is weird: normally in mask we have those bits set that are to be changed.
So amplitude mask should be bits that specify the amplitue, and this
should be
  reg &= ~MV88E6352_SERDES_OUT_AMP_MASK;
  reg |= val & MV88E6352_SERDES_OUT_AMP_MASK;
and mask should be defined inversely.

...

> +#define MV88E6352_SERDES_OUT_AMP_MASK		0xfffc

And this is also weird. 0xfffc is all bits set except last 2, but in
the mapping above the maximum value is 7, so you use 3 bits for
amplitude...

Marek

  parent reply	other threads:[~2022-02-08 16:12 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-08  9:44 [v4] dsa: mv88e6xxx: make serdes SGMII/Fiber tx amplitude configurable Holger Brunck
2022-02-08 13:48 ` Andrew Lunn
2022-02-08 18:51   ` Holger Brunck
2022-02-08 16:04 ` Marek Behún
2022-02-08 18:49   ` Holger Brunck
2022-02-08 16:12 ` Marek Behún [this message]
2022-02-08 18:44   ` Holger Brunck

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