[v4,1/3] net: stmmac: s32: use a syscon for S32_PHY_INTF_SEL_RGMII

[Simon Horman]

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---
    net: stmmac: s32: use a syscon for S32_PHY_INTF_SEL_RGMII

This commit adds syscon/regmap support for accessing the GMAC_0_CTRL_STS
register on s32 chipsets, while maintaining backwards compatibility with
the existing direct MMIO approach for older device trees.

> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-s32.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-s32.c
> index 5a485ee98fa7..2e6bb41f49e1 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-s32.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-s32.c

[ ... ]

> @@ -40,7 +44,10 @@ struct s32_priv_data {
>
>  static int s32_gmac_write_phy_intf_select(struct s32_priv_data *gmac)
>  {
> -	writel(S32_PHY_INTF_SEL_RGMII, gmac->ctrl_sts);
> +	if (gmac->ctrl_sts)
> +		writel(S32_PHY_INTF_SEL_RGMII, gmac->ctrl_sts);
> +	else
> +		regmap_write(gmac->sts_regmap, gmac->sts_offset, S32_PHY_INTF_SEL_RGMII);

Should the regmap_write() return value be checked here? The function
returns int and the caller s32_gmac_init() checks the return value
expecting errors to be propagated. For comparison, dwmac-sun55i.c in
sun55i_gmac200_set_syscon() does check regmap_write() return value:

    ret = regmap_write(regmap, SYSCON_REG, reg);
    if (ret < 0)
        return dev_err_probe(dev, ret, "Failed to write to syscon\n");

>
>  	dev_dbg(gmac->dev, "PHY mode set to %s\n", phy_modes(*gmac->intf_mode));
>
>  	return 0;

[ ... ]