Re: [PATCH] net: dsa: qca8k: Enable delay for RGMII_ID mode

From: Andrew Lunn <andrew@lunn.ch>
To: Vinod Koul <vkoul@kernel.org>
Cc: "David S Miller" <davem@davemloft.net>,
	linux-arm-msm@vger.kernel.org,
	"Bjorn Andersson" <bjorn.andersson@linaro.org>,
	netdev@vger.kernel.org,
	"Niklas Cassel" <niklas.cassel@linaro.org>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Michal Vokáč" <michal.vokac@ysoft.com>
Subject: Re: [PATCH] net: dsa: qca8k: Enable delay for RGMII_ID mode
Date: Mon, 18 Feb 2019 14:33:09 +0100	[thread overview]
Message-ID: <20190218133309.GB14879@lunn.ch> (raw)
In-Reply-To: <20190218130352.9373-1-vkoul@kernel.org>

On Mon, Feb 18, 2019 at 06:33:51PM +0530, Vinod Koul wrote:
> RGMII_ID specifies that we should have internal delay, so resurrect the
> delay addition routine but under the RGMII_ID mode.
> 
> Fixes: 40269aa9f40a ("net: dsa: qca8k: disable delay for RGMII mode")
> Signed-off-by: Vinod Koul <vkoul@kernel.org>
> ---
>  drivers/net/dsa/qca8k.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/net/dsa/qca8k.c b/drivers/net/dsa/qca8k.c
> index a4b6cda38016..aa1f7f1b20d3 100644
> --- a/drivers/net/dsa/qca8k.c
> +++ b/drivers/net/dsa/qca8k.c
> @@ -443,6 +443,18 @@ qca8k_set_pad_ctrl(struct qca8k_priv *priv, int port, int mode)
>  		val = QCA8K_PORT_PAD_RGMII_EN;
>  		qca8k_write(priv, reg, val);
>  		break;
> +	case PHY_INTERFACE_MODE_RGMII_ID:
> +		/* RGMII_ID needs internal delay. This is enabled through
> +		 * PORT5_PAD_CTRL for all ports, rather than individual port
> +		 * registers
> +		 */
> +		qca8k_write(priv, reg,
> +			    QCA8K_PORT_PAD_RGMII_EN |
> +			    QCA8K_PORT_PAD_RGMII_TX_DELAY(3) |
> +			    QCA8K_PORT_PAD_RGMII_RX_DELAY(3));
> +		qca8k_write(priv, QCA8K_REG_PORT5_PAD_CTRL,
> +			    QCA8K_PORT_PAD_RGMII_RX_DELAY_EN);
> +		break;

Hi Vinod

So i'm still confused if this is global, or per-port. The first
register written looks to be per-port, although only for ports 0 and
6. The second write seems to be global.

Is there a danger that port 0 has PHY_INTERFACE_MODE_RGMII_ID and port
6 has PHY_INTERFACE_MODE_RGMII, and we end up with delays disabled?
Maybe we should try to detect this, and return an error?

>  	case PHY_INTERFACE_MODE_SGMII:
>  		qca8k_write(priv, reg, QCA8K_PORT_PAD_SGMII_EN);
>  		break;

I think it would be good to add the other two PHY_INTERFACE_MODE_RGMII
modes to the default clause so we get an error reported that they are
not implemented.

    Andrew