linux-kernel - Re: [PATCH 1/3] net: stmmac: explicitly deassert GMAC_AHB

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Date:   Sat, 5 Jun 2021 22:24:45 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Matthew Hagan <mnhagan88@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Voon Weifeng <weifeng.voon@...el.com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Wong Vee Khee <vee.khee.wong@...ux.intel.com>,
        Tan Tee Min <tee.min.tan@...el.com>,
        "Wong, Vee Khee" <vee.khee.wong@...el.com>,
        Fugang Duan <fugang.duan@....com>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] net: stmmac: explicitly deassert GMAC_AHB_RESET

On Sat 05 Jun 12:35 CDT 2021, Matthew Hagan wrote:

> We are currently assuming that GMAC_AHB_RESET will already be deasserted
> by the bootloader. However if this has not been done, probing of the GMAC
> will fail. To remedy this we must ensure GMAC_AHB_RESET has been deasserted
> prior to probing.
> 

Sounds good, just some small style comments below.

> Signed-off-by: Matthew Hagan <mnhagan88@...il.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c     | 7 +++++++
>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 7 +++++++
>  include/linux/stmmac.h                                | 1 +
>  3 files changed, 15 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 6d41dd6f9f7a..1e28058b65a8 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -6840,6 +6840,13 @@ int stmmac_dvr_probe(struct device *device,
>  			reset_control_reset(priv->plat->stmmac_rst);
>  	}
>  
> +	if (priv->plat->stmmac_ahb_rst) {

You don't need this conditional, stmmac_ahb_rst will be NULL if not
specified and you can reset_control_deassert(NULL) without any problems.

> +		ret = reset_control_deassert(priv->plat->stmmac_ahb_rst);
> +		if (ret == -ENOTSUPP)
> +			dev_err(priv->device,
> +				"unable to bring out of ahb reset\n");

No need to wrap this line.

> +	}
> +
>  	/* Init MAC and get the capabilities */
>  	ret = stmmac_hw_init(priv);
>  	if (ret)
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index 97a1fedcc9ac..d8ae58bdbbe3 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -600,6 +600,13 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
>  		goto error_hw_init;
>  	}
>  
> +	plat->stmmac_ahb_rst = devm_reset_control_get_optional_shared(
> +							&pdev->dev, "ahb");
> +	if (IS_ERR(plat->stmmac_ahb_rst)) {
> +		ret = plat->stmmac_ahb_rst;

You need a PTR_ERR() around the plat->stmmac_ahb_rst.

Regards,
Bjorn

> +		goto error_hw_init;
> +	}
> +
>  	return plat;
>  
>  error_hw_init:
> diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> index e55a4807e3ea..9b6a64f3e3dc 100644
> --- a/include/linux/stmmac.h
> +++ b/include/linux/stmmac.h
> @@ -239,6 +239,7 @@ struct plat_stmmacenet_data {
>  	unsigned int mult_fact_100ns;
>  	s32 ptp_max_adj;
>  	struct reset_control *stmmac_rst;
> +	struct reset_control *stmmac_ahb_rst;
>  	struct stmmac_axi *axi;
>  	int has_gmac4;
>  	bool has_sun8i;
> -- 
> 2.26.3
>