netdev - Re: [Patch net-next 4/4] net: fec: Workaround for imx6sx enet tx hang when enable three queues

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Message-Id: <20140915.173509.929057672166230893.davem@davemloft.net>
Date:	Mon, 15 Sep 2014 17:35:09 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	Frank.Li@...escale.com
Cc:	b38611@...escale.com, netdev@...r.kernel.org, lznuaa@...il.com,
	shawn.guo@...aro.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [Patch net-next 4/4] net: fec: Workaround for imx6sx enet tx
 hang when enable three queues

From: <Frank.Li@...escale.com>
Date: Tue, 16 Sep 2014 01:12:57 +0800

> @@ -111,6 +111,13 @@ static void fec_enet_itr_coal_init(struct net_device *ndev);
>   *   independent rings
>   */
>  #define FEC_QUIRK_HAS_AVB		(1 << 8)
> +/*
> + * There is a TDAR race condition for mutliQ when the software sets TDAR
> + * and the UDMA clears TDAR simultaneously or in a small window (2-4 cycles).
> + * This will cause the udma_tx and udma_tx_arbiter state machines to hang.
> + * The issue exist at i.MX6SX enet IP.
> + */
> +#define FEC_QUIRK_TKT210582		(1 << 9)

Networking comments should be of the form:

	/* Like
	 * this.
	 */

>  	/* Trigger transmission start */
> -	writel(0, fep->hwp + FEC_X_DES_ACTIVE(queue));
> +	if (!(id_entry->driver_data & FEC_QUIRK_TKT210582) ||
> +		!readl(fep->hwp + FEC_X_DES_ACTIVE(queue)) ||
> +		!readl(fep->hwp + FEC_X_DES_ACTIVE(queue)) ||
> +		!readl(fep->hwp + FEC_X_DES_ACTIVE(queue)) ||
> +		!readl(fep->hwp + FEC_X_DES_ACTIVE(queue)))
> +		writel(0, fep->hwp + FEC_X_DES_ACTIVE(queue));

This conditional is not indented properly, see my feedback for patch #2.
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