netdev - Re: [PATCH net-next v2 3/3] net: stmmac: Configure AXI on Tegra234 MGBE

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Date: Mon, 5 Feb 2024 03:44:10 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Thierry Reding <thierry.reding@...il.com>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	Jose Abreu <joabreu@...opsys.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH net-next v2 3/3] net: stmmac: Configure AXI on Tegra234
 MGBE

On Fri, Feb 02, 2024 at 12:53:35PM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding@...dia.com>
> 
> Allow the device to use bursts and increase the maximum number of
> outstanding requests to improve performance. Measurements show an
> increase in throughput of around 5x on a 1 Gbps link.
> 
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c
> index bab57d1675df..b6bfa48f279d 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-tegra.c
> @@ -199,6 +199,12 @@ static void mgbe_uphy_lane_bringup_serdes_down(struct net_device *ndev, void *mg
>  	writel(value, mgbe->xpcs + XPCS_WRAP_UPHY_RX_CONTROL);
>  }
>  
> +static const struct stmmac_axi tegra234_mgbe_axi = {
> +	.axi_wr_osr_lmt = 63,
> +	.axi_rd_osr_lmt = 63,
> +	.axi_blen = { 256, },
> +};
> +
>  static int tegra_mgbe_probe(struct platform_device *pdev)
>  {
>  	struct plat_stmmacenet_data *plat;
> @@ -284,6 +290,9 @@ static int tegra_mgbe_probe(struct platform_device *pdev)
>  	if (err < 0)
>  		goto disable_clks;
>  
> +	/* setup default AXI configuration */
> +	res.axi = &tegra234_mgbe_axi;
> +
>  	plat = devm_stmmac_probe_config_dt(pdev, &res);
>  	if (IS_ERR(plat)) {
>  		err = PTR_ERR(plat);

The entire series can be converted to just a few lines of change:

 	plat = devm_stmmac_probe_config_dt(pdev, res.mac);
 	if (IS_ERR(plat)) {
 		err = PTR_ERR(plat);
 		goto disable_clks;
 	}
+
+	if (IS_ERR_OR_NULL(plat->axi)) {
+		plat->axi = devm_kzalloc(&pdev->dev, sizeof(*axi), GFP_KERNEL);
+		if (!plat->axi) {
+			ret = -ENOMEM;
+			goto disable_clks;
+		}
+	} /* else memset plat->axi with zeros if you wish */
+
+	plat->axi->axi_wr_osr_lmt = 63;
+	plat->axi->axi_rd_osr_lmt = 63;
+	plat->axi->axi_blen[0] = 256;
 
 	plat->has_xgmac = 1;
 	plat->flags |= STMMAC_FLAG_TSO_EN;
 	plat->pmt = 1;

Please don't overcomplicate the already overcomplicated driver with a
functionality which can be reached by the default one. In this case
the easiest way is to let the generic code work and then
override/replace/fix/etc the retrieved values. Thus there won't be
need in adding the redundant functionality and keep the generic
DT-platform code a bit simpler to read.

-Serge(y)

> 
> -- 
> 2.43.0
> 
>