linux-kernel - Re: [PATCH] net: stmmac: disable/enable ptp_ref

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Date:   Thu, 10 Oct 2019 16:01:03 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     Biao Huang <biao.huang@...iatek.com>
Cc:     <davem@...emloft.net>, Jose Abreu <joabreu@...opsys.com>,
        <andrew@...n.ch>, Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <netdev@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <yt.shen@...iatek.com>,
        <jianguo.zhang@...iatek.com>, <boon.leong.ong@...el.com>
Subject: Re: [PATCH] net: stmmac: disable/enable ptp_ref_clk in
 suspend/resume flow

On Wed, 9 Oct 2019 16:56:49 +0800, Biao Huang wrote:
> disable ptp_ref_clk in suspend flow, and enable it in resume flow.
> 
> Signed-off-by: Biao Huang <biao.huang@...iatek.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index c7c9e5f162e6..b592aeecc3dd 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -4469,6 +4469,8 @@ int stmmac_suspend(struct device *dev)
>  		stmmac_mac_set(priv, priv->ioaddr, false);
>  		pinctrl_pm_select_sleep_state(priv->device);
>  		/* Disable clock in case of PWM is off */
> +		if (priv->plat->clk_ptp_ref)
> +			clk_disable_unprepare(priv->plat->clk_ptp_ref);

I don't know much embedded, but it seems like this should perhaps just
be clk_disable() without the unprepare? stmmac_hw_teardown() is called
when driver is removed so it needs to unprepare as well.

Please feel free to explain to me why this needs to be
clk_disable_unprepare(), as I said - not an expert.

Also - if this is a bug fix and you'd like to have it backported to
older releases you need to add a Fixes tag.

Thanks!

>  		clk_disable(priv->plat->pclk);
>  		clk_disable(priv->plat->stmmac_clk);
>  	}
> @@ -4535,6 +4537,8 @@ int stmmac_resume(struct device *dev)
>  		/* enable the clk previously disabled */
>  		clk_enable(priv->plat->stmmac_clk);
>  		clk_enable(priv->plat->pclk);
> +		if (priv->plat->clk_ptp_ref)
> +			clk_prepare_enable(priv->plat->clk_ptp_ref);
>  		/* reset the phy so that it's ready */
>  		if (priv->mii)
>  			stmmac_mdio_reset(priv->mii);