netdev - Re: [PATCH net-next 05/12] net: ftgmac100: Convert using devm_clk_get_enabled() in ftgmac100_setup

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Message-ID: <7mfqy5mcwxrppb25j57za7jzk6d5llexfgnngl66tle3ic32yy@63cj63tsh3xh>
Date: Tue, 3 Sep 2024 17:52:20 +0200
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: Li Zetao <lizetao1@...wei.com>
Cc: florian.fainelli@...adcom.com, andrew@...n.ch, olteanv@...il.com, 
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	wens@...e.org, jernej.skrabec@...il.com, samuel@...lland.org, heiko@...ech.de, 
	yisen.zhuang@...wei.com, salil.mehta@...wei.com, hauke@...ke-m.de, 
	alexandre.torgue@...s.st.com, joabreu@...opsys.com, mcoquelin.stm32@...il.com, 
	wellslutw@...il.com, radhey.shyam.pandey@....com, michal.simek@....com, 
	ajay.kathat@...rochip.com, claudiu.beznea@...on.dev, kvalo@...nel.org, 
	jacky_chou@...eedtech.com, netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-sunxi@...ts.linux.dev, linux-rockchip@...ts.infradead.org, 
	linux-stm32@...md-mailman.stormreply.com, linux-wireless@...r.kernel.org
Subject: Re: [PATCH net-next 05/12] net: ftgmac100: Convert using
 devm_clk_get_enabled() in ftgmac100_setup_clk()

Hello,

On Tue, Sep 03, 2024 at 06:46:48PM +0800, Li Zetao wrote:
> 在 2024/9/3 16:09, Uwe Kleine-König 写道:
> > On Sat, Aug 31, 2024 at 10:13:27AM +0800, Li Zetao wrote:
> > > Use devm_clk_get_enabled() instead of devm_clk_get() +
> > > clk_prepare_enable(), which can make the clk consistent with the device
> > > life cycle and reduce the risk of unreleased clk resources. Since the
> > > device framework has automatically released the clk resource, there is
> > > no need to execute clk_disable_unprepare(clk) on the error path, drop
> > > the cleanup_clk label, and the original error process can return directly.
> > > 
> > > Signed-off-by: Li Zetao <lizetao1@...wei.com>
> > > ---
> > >   drivers/net/ethernet/faraday/ftgmac100.c | 27 ++++++------------------
> > >   1 file changed, 7 insertions(+), 20 deletions(-)
> > > 
> > > diff --git a/drivers/net/ethernet/faraday/ftgmac100.c b/drivers/net/ethernet/faraday/ftgmac100.c
> > > index 4c546c3aef0f..eb57c822c5ac 100644
> > > --- a/drivers/net/ethernet/faraday/ftgmac100.c
> > > +++ b/drivers/net/ethernet/faraday/ftgmac100.c
> > > @@ -1752,13 +1752,10 @@ static int ftgmac100_setup_clk(struct ftgmac100 *priv)
> > >   	struct clk *clk;
> > >   	int rc;
> > > -	clk = devm_clk_get(priv->dev, NULL /* MACCLK */);
> > > +	clk = devm_clk_get_enabled(priv->dev, NULL /* MACCLK */);
> > >   	if (IS_ERR(clk))
> > >   		return PTR_ERR(clk);
> > >   	priv->clk = clk;
> > > -	rc = clk_prepare_enable(priv->clk);
> > > -	if (rc)
> > > -		return rc;
> > >   	/* Aspeed specifies a 100MHz clock is required for up to
> > >   	 * 1000Mbit link speeds. As NCSI is limited to 100Mbit, 25MHz
> > > @@ -1767,21 +1764,17 @@ static int ftgmac100_setup_clk(struct ftgmac100 *priv)
> > >   	rc = clk_set_rate(priv->clk, priv->use_ncsi ? FTGMAC_25MHZ :
> > >   			  FTGMAC_100MHZ);
> > >   	if (rc)
> > > -		goto cleanup_clk;
> > > +		return rc;
> > >   	/* RCLK is for RMII, typically used for NCSI. Optional because it's not
> > >   	 * necessary if it's the AST2400 MAC, or the MAC is configured for
> > >   	 * RGMII, or the controller is not an ASPEED-based controller.
> > >   	 */
> > > -	priv->rclk = devm_clk_get_optional(priv->dev, "RCLK");
> > > -	rc = clk_prepare_enable(priv->rclk);
> > > -	if (!rc)
> > > -		return 0;
> > > +	priv->rclk = devm_clk_get_optional_enabled(priv->dev, "RCLK");
> > > +	if (IS_ERR(priv->rclk))
> > > +		return PTR_ERR(priv->rclk);
> > > -cleanup_clk:
> > > -	clk_disable_unprepare(priv->clk);
> > > -
> > > -	return rc;
> > > +	return 0;
> > 
> > You're changing semantics here. Before your patch ftgmac100_setup_clk()
> > was left with priv->clk disabled; now you keep it enabled.
> Before my patch, ftgmac100_setup_clk() was only left with priv->clk disabled
> when error occurs, and was left with priv->clk enabled when no error occurs
> because when enabling priv->rclk successfully, it will return 0 directly,
> and when enabling priv->rclk failed, it will disable priv->clk.
> 
> It turns out that the code logic is a bit counter-intuitive, but the
> readability has been improved after adjustments.

Indeed. This is IMHO worth mentioning in the commit log to prevent the
next reviewer stumble over the same code construct.

Best regards
Uwe

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