netdev - Re: [PATCH 3/3] net: stmmac: Use AVB mode by default

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Date:   Tue, 21 Mar 2017 15:23:00 +0000
From:   Joao Pinto <Joao.Pinto@...opsys.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        "David S . Miller" <davem@...emloft.net>
CC:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        "LABBE Corentin" <clabbe.montjoie@...il.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] net: stmmac: Use AVB mode by default

Às 3:12 PM de 3/21/2017, Thierry Reding escreveu:
> From: Thierry Reding <treding@...dia.com>
> 
> Prior to the recent multi-queue changes the driver would configure the
> queues to use the AVB mode, but the mode then got switched to DCB. The
> hardware still works fine in DCB mode, but my testing capabilities are
> limited, so it's safer to revert to the prior setting anyway.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  include/linux/stmmac.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/stmmac.h b/include/linux/stmmac.h
> index be47b859e954..8349a5c1537b 100644
> --- a/include/linux/stmmac.h
> +++ b/include/linux/stmmac.h
> @@ -56,8 +56,8 @@
>  #define MTL_RX_ALGORITHM_WSP	0x5
>  
>  /* RX/TX Queue Mode */
> -#define MTL_QUEUE_DCB		0x0
> -#define MTL_QUEUE_AVB		0x1
> +#define MTL_QUEUE_AVB		0x0
> +#define MTL_QUEUE_DCB		0x1
>  
>  /* The MDC clock could be set higher than the IEEE 802.3
>   * specified frequency limit 0f 2.5 MHz, by programming a clock divider
> 

Thierry, I don't understand this patch. It will have 0 impact.

In stmmac_platform configuration, 0 impact:

		if (of_property_read_bool(q_node, "snps,dcb-algorithm"))
			plat->rx_queues_cfg[queue].mode_to_use = MTL_QUEUE_DCB;
		else if (of_property_read_bool(q_node, "snps,avb-algorithm"))
			plat->rx_queues_cfg[queue].mode_to_use = MTL_QUEUE_AVB;
		else
**			plat->rx_queues_cfg[queue].mode_to_use = MTL_QUEUE_DCB;

In dwmac4_core, 0 impact:

	value &= GMAC_RX_QUEUE_CLEAR(queue);
	if (mode == MTL_QUEUE_AVB)
		value |= GMAC_RX_AV_QUEUE_ENABLE(queue);
	else if (mode == MTL_QUEUE_DCB)
		value |= GMAC_RX_DCB_QUEUE_ENABLE(queue);

I think you should set the default mode in (**).

Thanks.