netdev - Re: [PATCH net-next 2/2] net: stmmac: TBS support for platform driver

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Message-ID: <87v87g4hmy.fsf@geanix.com>
Date: Fri, 26 Jan 2024 09:35:01 +0100
From: Esben Haabendal <esben@...nix.com>
To: Rohan G Thomas <rohan.g.thomas@...el.com>
Cc: "David S . Miller" <davem@...emloft.net>,  Alexandre Torgue
 <alexandre.torgue@...s.st.com>,  Jose Abreu <joabreu@...opsys.com>,  Eric
 Dumazet <edumazet@...gle.com>,  Jakub Kicinski <kuba@...nel.org>,  Paolo
 Abeni <pabeni@...hat.com>,  Maxime Coquelin <mcoquelin.stm32@...il.com>,
  Rob Herring <robh+dt@...nel.org>,  Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>,  Conor Dooley <conor+dt@...nel.org>,
  Giuseppe Cavallaro <peppe.cavallaro@...com>,  Serge Semin
 <fancer.lancer@...il.com>,  netdev@...r.kernel.org,
  linux-stm32@...md-mailman.stormreply.com,
  linux-arm-kernel@...ts.infradead.org,  devicetree@...r.kernel.org,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] net: stmmac: TBS support for platform driver

Rohan G Thomas <rohan.g.thomas@...el.com> writes:

> Enable Time Based Scheduling(TBS) support for Tx queues through the
> stmmac platform driver. For this a new per-queue tx-config property,
> tbs-enabled is added to the devicetree.
>
> Commit 7eadf57290ec ("net: stmmac: pci: Enable TBS on GMAC5 IPK PCI
> entry") enables similar support for the stmmac pci driver.
>
> Also add check whether TBS support is available for a Tx DMA channel
> before enabling TBS support for that Tx DMA channel.
>
> Signed-off-by: Rohan G Thomas <rohan.g.thomas@...el.com>
> ---
>  .../net/ethernet/stmicro/stmmac/stmmac_main.c | 25 +++++++++++++++----
>  .../ethernet/stmicro/stmmac/stmmac_platform.c |  4 +++
>  2 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> index 81b6f3ecdf92..7333f0640b3d 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> @@ -3773,12 +3773,18 @@ stmmac_setup_dma_desc(struct stmmac_priv *priv, unsigned int mtu)
>  		dma_conf->dma_rx_size = DMA_DEFAULT_RX_SIZE;
>  
>  	/* Earlier check for TBS */
> -	for (chan = 0; chan < priv->plat->tx_queues_to_use; chan++) {
> -		struct stmmac_tx_queue *tx_q = &dma_conf->tx_queue[chan];
> -		int tbs_en = priv->plat->tx_queues_cfg[chan].tbs_en;
> +	if (priv->dma_cap.tbssel) {
> +		/* TBS is available only for tbs_ch_num of Tx DMA channels,
> +		 * starting from the highest Tx DMA channel.
> +		 */
> +		chan = priv->dma_cap.number_tx_channel - priv->dma_cap.tbs_ch_num;
> +		for (; chan < priv->plat->tx_queues_to_use; chan++) {
> +			struct stmmac_tx_queue *tx_q = &dma_conf->tx_queue[chan];
> +			int tbs_en = priv->plat->tx_queues_cfg[chan].tbs_en;
>  
> -		/* Setup per-TXQ tbs flag before TX descriptor alloc */
> -		tx_q->tbs |= tbs_en ? STMMAC_TBS_AVAIL : 0;
> +			/* Setup per-TXQ tbs flag before TX descriptor alloc */
> +			tx_q->tbs |= tbs_en ? STMMAC_TBS_AVAIL : 0;
> +		}
>  	}
>  
>  	ret = alloc_dma_desc_resources(priv, dma_conf);
> @@ -7505,6 +7511,15 @@ int stmmac_dvr_probe(struct device *device,
>  		}
>  	}
>  
> +	/* If TBS feature is supported(i.e. tbssel is true), then at least 1 Tx
> +	 * DMA channel supports TBS. So if tbs_ch_num is 0 and tbssel is true,
> +	 * assume all Tx DMA channels support TBS. TBS_CH field, which gives
> +	 * number of Tx DMA channels with TBS support is only available only for
> +	 * DW xGMAC IP. For other DWMAC IPs all Tx DMA channels can support TBS.

The Ethernet QOS controllers found in various i.MX socs does not support
TBS on TX queue 0. I believe this patch would break the dwmac driver for
these platforms.

> +	 */
> +	if (priv->dma_cap.tbssel && !priv->dma_cap.tbs_ch_num)
> +		priv->dma_cap.tbs_ch_num = priv->dma_cap.number_tx_channel;
> +
>  	ndev->features |= ndev->hw_features | NETIF_F_HIGHDMA;
>  	ndev->watchdog_timeo = msecs_to_jiffies(watchdog);
>  #ifdef STMMAC_VLAN_TAG_USED
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index 843bd8804bfa..6c0191c84071 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -279,6 +279,10 @@ static int stmmac_mtl_setup(struct platform_device *pdev,
>  		plat->tx_queues_cfg[queue].coe_unsupported =
>  			of_property_read_bool(q_node, "snps,coe-unsupported");
>  
> +		/* Select TBS for supported queues */
> +		plat->tx_queues_cfg[queue].tbs_en =
> +			of_property_read_bool(q_node, "snps,tbs-enabled");
> +
>  		queue++;
>  	}
>  	if (queue != plat->tx_queues_to_use) {

/Esben