linux-kernel - Re: [PATCH V3 net-next 1/4] net: ethernet: stmmac: Add support for syscfg clock

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Message-ID: <20191106181240.GG30762@lunn.ch>
Date:   Wed, 6 Nov 2019 19:12:40 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Christophe Roullier <christophe.roullier@...com>
Cc:     robh@...nel.org, davem@...emloft.net, joabreu@...opsys.com,
        mark.rutland@....com, mcoquelin.stm32@...il.com,
        alexandre.torgue@...com, peppe.cavallaro@...com,
        linux-stm32@...md-mailman.stormreply.com,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org
Subject: Re: [PATCH V3 net-next 1/4] net: ethernet: stmmac: Add support for
 syscfg clock

On Wed, Nov 06, 2019 at 11:12:17AM +0100, Christophe Roullier wrote:
> Add optional support for syscfg clock in dwmac-stm32.c
> Now Syscfg clock is activated automatically when syscfg
> registers are used
> 
> Signed-off-by: Christophe Roullier <christophe.roullier@...com>
> ---
>  .../net/ethernet/stmicro/stmmac/dwmac-stm32.c | 28 +++++++++++--------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> index 4ef041bdf6a1..be7d58d83cfa 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-stm32.c
> @@ -152,19 +152,24 @@ static int stm32mp1_clk_prepare(struct stm32_dwmac *dwmac, bool prepare)
>  	int ret = 0;
>  
>  	if (prepare) {
> -		ret = clk_prepare_enable(dwmac->syscfg_clk);
> -		if (ret)
> -			return ret;
> -
> +		if (dwmac->syscfg_clk) {
> +			ret = clk_prepare_enable(dwmac->syscfg_clk);
> +			if (ret)
> +				return ret;
> +		}

Hi Christophe

I think you did not understand what i said.  clk_prepare_enable() is
happy to take a NULL pointer. So you don't need this new guard. You
don't need this change at all.

>  		if (dwmac->clk_eth_ck) {
>  			ret = clk_prepare_enable(dwmac->clk_eth_ck);
>  			if (ret) {
> -				clk_disable_unprepare(dwmac->syscfg_clk);
> +				if (dwmac->syscfg_clk)
> +					clk_disable_unprepare
> +						(dwmac->syscfg_clk);

clk_disable_unprepare() is happy to take a NULL pointer...

	Andrew