netdev - Re: [PATCH net-next v5 3/5] net: ti: icssg-prueth: Add support for HSR frame forward offload

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Message-ID: <cf462ca8-08bd-42bd-965a-88e28e63bb3f@kernel.org>
Date: Tue, 10 Sep 2024 15:12:20 +0300
From: Roger Quadros <rogerq@...nel.org>
To: MD Danish Anwar <danishanwar@...com>, robh@...nel.org,
 jan.kiszka@...mens.com, dan.carpenter@...aro.org, saikrishnag@...vell.com,
 andrew@...n.ch, javier.carrasco.cruz@...il.com, jacob.e.keller@...el.com,
 diogo.ivo@...mens.com, horms@...nel.org, richardcochran@...il.com,
 pabeni@...hat.com, kuba@...nel.org, edumazet@...gle.com, davem@...emloft.net
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, srk@...com,
 Vignesh Raghavendra <vigneshr@...com>
Subject: Re: [PATCH net-next v5 3/5] net: ti: icssg-prueth: Add support for
 HSR frame forward offload

Hi,

On 06/09/2024 14:15, MD Danish Anwar wrote:
> Add support for offloading HSR port-to-port frame forward to hardware.
> When the slave interfaces are added to the HSR interface, the PRU cores
> will be stopped and ICSSG HSR firmwares will be loaded to them.
> 
> Similarly, when HSR interface is deleted, the PRU cores will be
> restarted and the last used firmwares will be reloaded. PRUeth
> interfaces will be back to the last used mode.
> 
> This commit also renames some APIs that are common between switch and
> hsr mode with '_fw_offload' suffix.
> 
> Signed-off-by: MD Danish Anwar <danishanwar@...com>
> ---
>  .../net/ethernet/ti/icssg/icssg_classifier.c  |   1 +
>  drivers/net/ethernet/ti/icssg/icssg_config.c  |  18 +--
>  drivers/net/ethernet/ti/icssg/icssg_prueth.c  | 132 +++++++++++++++++-
>  drivers/net/ethernet/ti/icssg/icssg_prueth.h  |   6 +
>  4 files changed, 145 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/net/ethernet/ti/icssg/icssg_classifier.c b/drivers/net/ethernet/ti/icssg/icssg_classifier.c
> index 9ec504d976d6..833ca86d0b71 100644
> --- a/drivers/net/ethernet/ti/icssg/icssg_classifier.c
> +++ b/drivers/net/ethernet/ti/icssg/icssg_classifier.c

<snip>

> +static void emac_change_hsr_feature(struct net_device *ndev,
> +				    netdev_features_t features,
> +				    u64 hsr_feature)
> +{
> +	netdev_features_t changed = ndev->features ^ features;
> +
> +	if (changed & hsr_feature) {
> +		if (features & hsr_feature)
> +			ndev->features |= hsr_feature;
> +		else
> +			ndev->features &= ~hsr_feature;

You are not supposed to change ndev->features here.

From
"https://www.kernel.org/doc/Documentation/networking/netdev-features.txt"
"
 * ndo_set_features:

Hardware should be reconfigured to match passed feature set. The set
should not be altered unless some error condition happens that can't
be reliably detected in ndo_fix_features. In this case, the callback
should update netdev->features to match resulting hardware state.
Errors returned are not (and cannot be) propagated anywhere except dmesg.
(Note: successful return is zero, >0 means silent error.)"

This means only in 

> +	}
> +}
> +
> +static int emac_ndo_set_features(struct net_device *ndev,
> +				 netdev_features_t features)
> +{
> +	emac_change_hsr_feature(ndev, features, NETIF_F_HW_HSR_FWD);
> +	emac_change_hsr_feature(ndev, features, NETIF_F_HW_HSR_DUP);
> +	emac_change_hsr_feature(ndev, features, NETIF_F_HW_HSR_TAG_INS);
> +	emac_change_hsr_feature(ndev, features, NETIF_F_HW_HSR_TAG_RM);

I don't understand this part. 

As you are not changing hardware state in ndo_set_features, I'm not sure why
you even need ndo_set_features callback.

You didn't take my feedback about using ndo_fix_features().

Please read this.
https://www.kernel.org/doc/Documentation/networking/netdev-features.txt
"Part II: Controlling enabled features"
"Part III: Implementation hints"

Also look at how _netdev_update_features() works and calls ndo_fix_features()
and ndo_set_features()

https://elixir.bootlin.com/linux/v6.11-rc7/source/net/core/dev.c#L10023

> +
> +	return 0;
> +}
> +
>  static const struct net_device_ops emac_netdev_ops = {
>  	.ndo_open = emac_ndo_open,
>  	.ndo_stop = emac_ndo_stop,
> @@ -737,6 +780,7 @@ static const struct net_device_ops emac_netdev_ops = {
>  	.ndo_eth_ioctl = icssg_ndo_ioctl,
>  	.ndo_get_stats64 = icssg_ndo_get_stats64,
>  	.ndo_get_phys_port_name = icssg_ndo_get_phys_port_name,
> +	.ndo_set_features = emac_ndo_set_features,
>  };

<snip>

-- 
cheers,
-roger