netdev - Re: [RFC PATCH] can: flexcan: add ethtool support to get rx/tx ring parameters

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Date:   Sat, 8 Jan 2022 21:16:50 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc:     linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH] can: flexcan: add ethtool support to get rx/tx ring
 parameters

On 08.01.2022 19:16:33, Dario Binacchi wrote:
> Adds ethtool support to get the number of message buffers configured for
> reception/transmission, which may also depends on runtime configurations
> such as the 'rx-rtr' flag state.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> 
> ---
> 
>  drivers/net/can/flexcan/flexcan-ethtool.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/net/can/flexcan/flexcan-ethtool.c b/drivers/net/can/flexcan/flexcan-ethtool.c
> index 5bb45653e1ac..d119bca584f6 100644
> --- a/drivers/net/can/flexcan/flexcan-ethtool.c
> +++ b/drivers/net/can/flexcan/flexcan-ethtool.c
> @@ -80,7 +80,24 @@ static int flexcan_set_priv_flags(struct net_device *ndev, u32 priv_flags)
>  	return 0;
>  }
>  
> +static void flexcan_get_ringparam(struct net_device *ndev,
> +				  struct ethtool_ringparam *ring)

This doesn't compile on net-next/master, as the prototype of the
get_ringparam callback changed, fixed this while applying.

> +{
> +	struct flexcan_priv *priv = netdev_priv(ndev);
> +
> +	ring->rx_max_pending = priv->mb_count;
> +	ring->tx_max_pending = priv->mb_count;
> +
> +	if (priv->devtype_data.quirks & FLEXCAN_QUIRK_USE_RX_MAILBOX)
> +		ring->rx_pending = __sw_hweight64(priv->rx_mask);

I've replaced the hamming weight calculation by the simpler:

| 		ring->rx_pending = priv->offload.mb_last -
| 			priv->offload.mb_first + 1;

> +	else
> +		ring->rx_pending = 6;
> +
> +	ring->tx_pending = __sw_hweight64(priv->tx_mask);

...and here I added a hardcoded "1", as the driver currently only
support on TX buffer.

> +}
> +
>  static const struct ethtool_ops flexcan_ethtool_ops = {
> +	.get_ringparam = flexcan_get_ringparam,
>  	.get_sset_count = flexcan_get_sset_count,
>  	.get_strings = flexcan_get_strings,
>  	.get_priv_flags = flexcan_get_priv_flags,

BTW: If you're looking for more TX performance, this can be done by
using more than one TX buffer. It's also possible to configure the
number of RX and TX buffers via ethtool during runtime. I'm currently
preparing a patch set for the mcp251xfd to implement this.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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