linux-kernel - Re: [PATCH net-next 3/3] net: stmmac: Add glue layer for Spacemit K3 SoC

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Message-ID: <aW9jbqBSgkiLLw8r@pie>
Date: Tue, 20 Jan 2026 11:13:50 +0000
From: Yao Zi <me@...ao.cc>
To: Inochi Amaoto <inochiama@...il.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Yixun Lan <dlan@...too.org>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Richard Cochran <richardcochran@...il.com>,
	Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, Alexandre Ghiti <alex@...ti.fr>,
	"Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
	Yanteng Si <siyanteng@...oftware.com.cn>,
	Yao Zi <ziyao@...root.org>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>,
	Chen-Yu Tsai <wens@...nel.org>,
	Shangjuan Wei <weishangjuan@...incomputing.com>,
	Boon Khai Ng <boon.khai.ng@...era.com>,
	Quentin Schulz <quentin.schulz@...rry.de>,
	Giuseppe Cavallaro <peppe.cavallaro@...com>,
	Jose Abreu <joabreu@...opsys.com>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
	spacemit@...ts.linux.dev, linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org,
	Longbin Li <looong.bin@...il.com>
Subject: Re: [PATCH net-next 3/3] net: stmmac: Add glue layer for Spacemit K3
 SoC

On Tue, Jan 20, 2026 at 12:36:08PM +0800, Inochi Amaoto wrote:
> Adds Spacemit dwmac driver support on the Spacemit K3 SoC.
> 
> Signed-off-by: Inochi Amaoto <inochiama@...il.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/Kconfig   |  12 +
>  drivers/net/ethernet/stmicro/stmmac/Makefile  |   1 +
>  .../ethernet/stmicro/stmmac/dwmac-spacemit.c  | 224 ++++++++++++++++++
>  3 files changed, 237 insertions(+)
>  create mode 100644 drivers/net/ethernet/stmicro/stmmac/dwmac-spacemit.c

...

> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-spacemit.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-spacemit.c
> new file mode 100644
> index 000000000000..72744e60d02a
> --- /dev/null
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-spacemit.c
> @@ -0,0 +1,224 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Spacemit DWMAC platform driver
> + *
> + * Copyright (C) 2026 Inochi Amaoto <inochiama@...il.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/math.h>

These are the only two headers listed out-of-order. Is this intended?

> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/regmap.h>

...

> +static int spacemit_dwmac_detected_delay_value(unsigned int delay,
> +					       unsigned int *config)
> +{
> +	int i;
> +	int code, best_code = 0;
> +	unsigned int best_delay = 0;
> +	unsigned int best_config = 0;
> +
> +	if (delay == 0)
> +		return 0;
> +
> +	for (i = 0; i < ARRAY_SIZE(k3_delay_step_10x); i++) {
> +		unsigned int step = k3_delay_step_10x[i];
> +
> +		for (code = 1; code <= MAX_DLINE_DELAY_CODE; code++) {
> +			/*
> +			 * Note K3 require a specific factor for calculate
> +			 * the delay, in this scenario it is 0.9. So the
> +			 * formula is code * step / 10 * 0.9
> +			 */
> +			unsigned int tmp = code * step * 9 / 10 / 10;
> +
> +			if (abs(tmp - delay) < abs(best_delay - delay)) {
> +				best_code = code;
> +				best_delay = tmp;
> +				best_config = i;
> +			}

Is the inner loop really necessary? Could it be replaced by

	this_code = DIV_ROUND_CLOSEST(delay * 10 * 10, step * 9);
	this_delay = this_code * step * 9 / 10 / 10;

Then comparing abs(this_delay - delay) and abs(best_delay - delay)?

> +		}
> +	}
> +
> +	*config = best_config;
> +
> +	return best_code;
> +}

...

> +static int spacemit_dwmac_update_ifconfig(struct plat_stmmacenet_data *plat_dat,
> +					  struct stmmac_resources *stmmac_res,
> +					  struct regmap *apmu,
> +					  unsigned int ctrl_offset)
> +{
> +	unsigned int mask = PHY_INTF_MII | PHY_INTF_RGMII | WAKE_IRQ_EN;
> +	unsigned int val = 0;
> +
> +	switch (plat_dat->phy_interface) {
> +	case PHY_INTERFACE_MODE_MII:
> +		val |= PHY_INTF_MII;
> +		break;

The OR operation seems unnecessary and could be replaced with an
assignment. Same for PHY_INTERFACE_MODE_RGMII's case.

> +
> +	case PHY_INTERFACE_MODE_RMII:
> +		break;
> +
> +	case PHY_INTERFACE_MODE_RGMII:
> +	case PHY_INTERFACE_MODE_RGMII_ID:
> +	case PHY_INTERFACE_MODE_RGMII_RXID:
> +	case PHY_INTERFACE_MODE_RGMII_TXID:
> +		val |= PHY_INTF_RGMII;
> +		break;
> +
> +	default:
> +		return -EOPNOTSUPP;
> +	}

...

> +static int spacemit_dwmac_probe(struct platform_device *pdev)
> +{

...

> +	of_property_read_u32(pdev->dev.of_node, "tx-internal-delay-ps", &tx_delay);
> +	of_property_read_u32(pdev->dev.of_node, "rx-internal-delay-ps", &rx_delay);

According to of.h, of_property_read_u32, which in turn calls
of_property_read_u32_array, could fail with -ENODATA if there's no value
associated with the property. Should the case be handled?

Regards,
Yao Zi