linux-kernel - Re: [PATCH net] net: stmmac: dwmac-socfpga: Don't access SGMII adapter when not available

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Message-ID: <20231128101841.627fc97e@windsurf>
Date:   Tue, 28 Nov 2023 10:18:41 +0100
From:   Thomas Petazzoni <thomas.petazzoni@...tlin.com>
To:     Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Simon Horman <horms@...nel.org>,
        linux-stm32@...md-mailman.stormreply.com,
        alexis.lothore@...tlin.com
Subject: Re: [PATCH net] net: stmmac: dwmac-socfpga: Don't access SGMII
 adapter when not available

On Tue, 28 Nov 2023 10:45:37 +0100
Maxime Chevallier <maxime.chevallier@...tlin.com> wrote:

> The SGMII adapter isn't present on all dwmac-socfpga implementations.
> Make sure we don't try to configure it if we don't have this adapter.
> 
> Fixes: 5d1f3fe7d2d5 ("net: stmmac: dwmac-sogfpga: use the lynx pcs driver")
> Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
> index ba2ce776bd4d..ae120792e1b6 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-socfpga.c
> @@ -243,7 +243,8 @@ static void socfpga_sgmii_config(struct socfpga_dwmac *dwmac, bool enable)
>  {
>  	u16 val = enable ? SGMII_ADAPTER_ENABLE : SGMII_ADAPTER_DISABLE;
>  
> -	writew(val, dwmac->sgmii_adapter_base + SGMII_ADAPTER_CTRL_REG);
> +	if (dwmac->sgmii_adapter_base)
> +		writew(val, dwmac->sgmii_adapter_base + SGMII_ADAPTER_CTRL_REG);
>  }
>  
>  static int socfpga_set_phy_mode_common(int phymode, u32 *val)

Reviewed-by: Thomas Petazzoni <thomas.petazzoni@...tlin.com>

As a follow-up improvement, there's an open-coded version of
socfpga_sgmii_config() in socfpga_dwmac_fix_mac_speed(), which could be
rewritten as such:

	socfpga_sgmii_config(dwmac, false);

	if (splitter_base) {
		val = readl(splitter_base + EMAC_SPLITTER_CTRL_REG);
		val &= ~EMAC_SPLITTER_CTRL_SPEED_MASK;

		switch (speed) {
		case 1000:
			val |= EMAC_SPLITTER_CTRL_SPEED_1000;
			break;
		case 100:
			val |= EMAC_SPLITTER_CTRL_SPEED_100;
			break;
		case 10:
			val |= EMAC_SPLITTER_CTRL_SPEED_10;
			break;
		default:
			return;
		}
		writel(val, splitter_base + EMAC_SPLITTER_CTRL_REG);
	}

	if (phy_dev)
		socfpga_sgmii_config(dwmac, true);

But of course, that's not a fix so it should be a separate improvement.

Best regards,

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com