netdev - Re: [PATCH v1 net-next] e1000e: Remove duplicated writel() in e1000_configure

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Message-ID: <87af1b9e-21c3-4c22-861a-b917b5cd82c2@lunn.ch>
Date: Mon, 2 Sep 2024 18:04:36 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Takamitsu Iwai <takamitz@...zon.co.jp>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH v1 net-next] e1000e: Remove duplicated writel() in
 e1000_configure_tx/rx()

On Mon, Sep 02, 2024 at 03:14:54PM +0900, Takamitsu Iwai wrote:
> Duplicated register initialization codes exist in e1000_configure_tx()
> and e1000_configure_rx().

What does the datasheet say about these registers? Since we are
talking about hardware here, before you remove anything you need to be
sure these writes are not actually required by the hardware.

> commit 0845d45e900c ("e1000e: Modify Tx/Rx configurations to avoid
> null pointer dereferences in e1000_open") has introduced these
> writel(). This commit moved register writing to
> e1000_configure_tx/rx(), and as result, it caused duplication in
> e1000_configure_tx/rx().

Did the same sequence of read/writes happen before 0845d45e900c? Or
did 0845d45e900c add additional writes, not just move them around?

	Andrew