[PATCH net-next] net: stmmac: sun8i: drop unneeded default syscon value

[PATCH net-next] net: stmmac: sun8i: drop unneeded default syscon value

[Andre Przywara]

For some odd reason we were very jealous about the value of the EMAC
clock register from the syscon block, insisting on a reset value and
only doing read-modify-write operations on that register, even though we
pretty much know the register layout.
This already led to a basically redundant entry for the H6, which only
differs by that value. We seem to have the same situation with the new
A523 SoC, which again is compatible to the A64, but has a different
syscon reset value.

Drop any assumptions about that value, and set or clear the bits that we
want to program, from scratch (starting with a value of 0). For the
remove() implementation, we just turn on the POWERDOWN bit, and deselect
the internal PHY, which mimics the existing code.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Acked-by: Corentin LABBE <clabbe.montjoie@gmail.com>
Tested-by: Corentin LABBE <clabbe.montjoie@gmail.com>
Tested-by: Paul Kocialkowski <paulk@sys-base.io>
Reviewed-by: Paul Kocialkowski <paulk@sys-base.io>
---
Hi,

this follows up on my RFC post from April[1]. We figured that the old
approach (insisting on a certain reset value) was never really needed, and
some people tested this on various hardware, many thanks for that!

No real changes except solving one conflict after rebasing on top of
v6.17-rc1, and adding the tags from the diligent reviewers!

Cheers,
Andre

[1] https://lore.kernel.org/netdev/20250423095222.1517507-1-andre.przywara@arm.com/

 .../net/ethernet/stmicro/stmmac/dwmac-sun8i.c | 47 ++-----------------
 1 file changed, 4 insertions(+), 43 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
index 2796dc426943e..690f3650f84ed 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
@@ -31,10 +31,6 @@
  */
 
 /* struct emac_variant - Describe dwmac-sun8i hardware variant
- * @default_syscon_value:	The default value of the EMAC register in syscon
- *				This value is used for disabling properly EMAC
- *				and used as a good starting value in case of the
- *				boot process(uboot) leave some stuff.
  * @syscon_field		reg_field for the syscon's gmac register
  * @soc_has_internal_phy:	Does the MAC embed an internal PHY
  * @support_mii:		Does the MAC handle MII
@@ -48,7 +44,6 @@
  *				value of zero indicates this is not supported.
  */
 struct emac_variant {
-	u32 default_syscon_value;
 	const struct reg_field *syscon_field;
 	bool soc_has_internal_phy;
 	bool support_mii;
@@ -94,7 +89,6 @@ static const struct reg_field sun8i_ccu_reg_field = {
 };
 
 static const struct emac_variant emac_variant_h3 = {
-	.default_syscon_value = 0x58000,
 	.syscon_field = &sun8i_syscon_reg_field,
 	.soc_has_internal_phy = true,
 	.support_mii = true,
@@ -105,14 +99,12 @@ static const struct emac_variant emac_variant_h3 = {
 };
 
 static const struct emac_variant emac_variant_v3s = {
-	.default_syscon_value = 0x38000,
 	.syscon_field = &sun8i_syscon_reg_field,
 	.soc_has_internal_phy = true,
 	.support_mii = true
 };
 
 static const struct emac_variant emac_variant_a83t = {
-	.default_syscon_value = 0,
 	.syscon_field = &sun8i_syscon_reg_field,
 	.soc_has_internal_phy = false,
 	.support_mii = true,
@@ -122,7 +114,6 @@ static const struct emac_variant emac_variant_a83t = {
 };
 
 static const struct emac_variant emac_variant_r40 = {
-	.default_syscon_value = 0,
 	.syscon_field = &sun8i_ccu_reg_field,
 	.support_mii = true,
 	.support_rgmii = true,
@@ -130,7 +121,6 @@ static const struct emac_variant emac_variant_r40 = {
 };
 
 static const struct emac_variant emac_variant_a64 = {
-	.default_syscon_value = 0,
 	.syscon_field = &sun8i_syscon_reg_field,
 	.soc_has_internal_phy = false,
 	.support_mii = true,
@@ -141,7 +131,6 @@ static const struct emac_variant emac_variant_a64 = {
 };
 
 static const struct emac_variant emac_variant_h6 = {
-	.default_syscon_value = 0x50000,
 	.syscon_field = &sun8i_syscon_reg_field,
 	/* The "Internal PHY" of H6 is not on the die. It's on the
 	 * co-packaged AC200 chip instead.
@@ -933,25 +922,11 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
 	struct sunxi_priv_data *gmac = plat->bsp_priv;
 	struct device_node *node = dev->of_node;
 	int ret;
-	u32 reg, val;
-
-	ret = regmap_field_read(gmac->regmap_field, &val);
-	if (ret) {
-		dev_err(dev, "Fail to read from regmap field.\n");
-		return ret;
-	}
-
-	reg = gmac->variant->default_syscon_value;
-	if (reg != val)
-		dev_warn(dev,
-			 "Current syscon value is not the default %x (expect %x)\n",
-			 val, reg);
+	u32 reg = 0, val;
 
 	if (gmac->variant->soc_has_internal_phy) {
 		if (of_property_read_bool(node, "allwinner,leds-active-low"))
 			reg |= H3_EPHY_LED_POL;
-		else
-			reg &= ~H3_EPHY_LED_POL;
 
 		/* Force EPHY xtal frequency to 24MHz. */
 		reg |= H3_EPHY_CLK_SEL;
@@ -965,11 +940,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
 		 * address. No need to mask it again.
 		 */
 		reg |= ret << H3_EPHY_ADDR_SHIFT;
-	} else {
-		/* For SoCs without internal PHY the PHY selection bit should be
-		 * set to 0 (external PHY).
-		 */
-		reg &= ~H3_EPHY_SELECT;
 	}
 
 	if (!of_property_read_u32(node, "allwinner,tx-delay-ps", &val)) {
@@ -980,8 +950,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
 		val /= 100;
 		dev_dbg(dev, "set tx-delay to %x\n", val);
 		if (val <= gmac->variant->tx_delay_max) {
-			reg &= ~(gmac->variant->tx_delay_max <<
-				 SYSCON_ETXDC_SHIFT);
 			reg |= (val << SYSCON_ETXDC_SHIFT);
 		} else {
 			dev_err(dev, "Invalid TX clock delay: %d\n",
@@ -998,8 +966,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
 		val /= 100;
 		dev_dbg(dev, "set rx-delay to %x\n", val);
 		if (val <= gmac->variant->rx_delay_max) {
-			reg &= ~(gmac->variant->rx_delay_max <<
-				 SYSCON_ERXDC_SHIFT);
 			reg |= (val << SYSCON_ERXDC_SHIFT);
 		} else {
 			dev_err(dev, "Invalid RX clock delay: %d\n",
@@ -1008,11 +974,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
 		}
 	}
 
-	/* Clear interface mode bits */
-	reg &= ~(SYSCON_ETCS_MASK | SYSCON_EPIT);
-	if (gmac->variant->support_rmii)
-		reg &= ~SYSCON_RMII_EN;
-
 	switch (plat->mac_interface) {
 	case PHY_INTERFACE_MODE_MII:
 		/* default */
@@ -1039,9 +1000,9 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
 
 static void sun8i_dwmac_unset_syscon(struct sunxi_priv_data *gmac)
 {
-	u32 reg = gmac->variant->default_syscon_value;
-
-	regmap_field_write(gmac->regmap_field, reg);
+	if (gmac->variant->soc_has_internal_phy)
+		regmap_field_write(gmac->regmap_field,
+				   (H3_EPHY_SHUTDOWN | H3_EPHY_SELECT));
 }
 
 static void sun8i_dwmac_exit(struct platform_device *pdev, void *priv)
-- 
2.46.3

Re: [PATCH net-next] net: stmmac: sun8i: drop unneeded default syscon value

[Jacob Keller]

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On 8/25/2025 10:20 AM, Andre Przywara wrote:
> For some odd reason we were very jealous about the value of the EMAC
> clock register from the syscon block, insisting on a reset value and
> only doing read-modify-write operations on that register, even though we
> pretty much know the register layout.
> This already led to a basically redundant entry for the H6, which only
> differs by that value. We seem to have the same situation with the new
> A523 SoC, which again is compatible to the A64, but has a different
> syscon reset value.
> 
> Drop any assumptions about that value, and set or clear the bits that we
> want to program, from scratch (starting with a value of 0). For the
> remove() implementation, we just turn on the POWERDOWN bit, and deselect
> the internal PHY, which mimics the existing code.
> 
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> Reviewed-by: Jernej Skrabec <jernej.skrabec@gmail.com>
> Acked-by: Corentin LABBE <clabbe.montjoie@gmail.com>
> Tested-by: Corentin LABBE <clabbe.montjoie@gmail.com>
> Tested-by: Paul Kocialkowski <paulk@sys-base.io>
> Reviewed-by: Paul Kocialkowski <paulk@sys-base.io>
> ---
> Hi,
> 
> this follows up on my RFC post from April[1]. We figured that the old
> approach (insisting on a certain reset value) was never really needed, and
> some people tested this on various hardware, many thanks for that!
> 
> No real changes except solving one conflict after rebasing on top of
> v6.17-rc1, and adding the tags from the diligent reviewers!
> 
> Cheers,
> Andre
> 

Makes sense. Its simpler to build up from 0 instead of trying to build
up from the current baseline with a warning that was unnecessary.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

> [1] https://lore.kernel.org/netdev/20250423095222.1517507-1-andre.przywara@arm.com/
> 
>  .../net/ethernet/stmicro/stmmac/dwmac-sun8i.c | 47 ++-----------------
>  1 file changed, 4 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
> index 2796dc426943e..690f3650f84ed 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
> @@ -31,10 +31,6 @@
>   */
>  
>  /* struct emac_variant - Describe dwmac-sun8i hardware variant
> - * @default_syscon_value:	The default value of the EMAC register in syscon
> - *				This value is used for disabling properly EMAC
> - *				and used as a good starting value in case of the
> - *				boot process(uboot) leave some stuff.
>   * @syscon_field		reg_field for the syscon's gmac register
>   * @soc_has_internal_phy:	Does the MAC embed an internal PHY
>   * @support_mii:		Does the MAC handle MII
> @@ -48,7 +44,6 @@
>   *				value of zero indicates this is not supported.
>   */
>  struct emac_variant {
> -	u32 default_syscon_value;
>  	const struct reg_field *syscon_field;
>  	bool soc_has_internal_phy;
>  	bool support_mii;
> @@ -94,7 +89,6 @@ static const struct reg_field sun8i_ccu_reg_field = {
>  };
>  
>  static const struct emac_variant emac_variant_h3 = {
> -	.default_syscon_value = 0x58000,
>  	.syscon_field = &sun8i_syscon_reg_field,
>  	.soc_has_internal_phy = true,
>  	.support_mii = true,
> @@ -105,14 +99,12 @@ static const struct emac_variant emac_variant_h3 = {
>  };
>  
>  static const struct emac_variant emac_variant_v3s = {
> -	.default_syscon_value = 0x38000,
>  	.syscon_field = &sun8i_syscon_reg_field,
>  	.soc_has_internal_phy = true,
>  	.support_mii = true
>  };
>  
>  static const struct emac_variant emac_variant_a83t = {
> -	.default_syscon_value = 0,
>  	.syscon_field = &sun8i_syscon_reg_field,
>  	.soc_has_internal_phy = false,
>  	.support_mii = true,
> @@ -122,7 +114,6 @@ static const struct emac_variant emac_variant_a83t = {
>  };
>  
>  static const struct emac_variant emac_variant_r40 = {
> -	.default_syscon_value = 0,
>  	.syscon_field = &sun8i_ccu_reg_field,
>  	.support_mii = true,
>  	.support_rgmii = true,
> @@ -130,7 +121,6 @@ static const struct emac_variant emac_variant_r40 = {
>  };
>  
>  static const struct emac_variant emac_variant_a64 = {
> -	.default_syscon_value = 0,
>  	.syscon_field = &sun8i_syscon_reg_field,
>  	.soc_has_internal_phy = false,
>  	.support_mii = true,
> @@ -141,7 +131,6 @@ static const struct emac_variant emac_variant_a64 = {
>  };
>  
>  static const struct emac_variant emac_variant_h6 = {
> -	.default_syscon_value = 0x50000,
>  	.syscon_field = &sun8i_syscon_reg_field,
>  	/* The "Internal PHY" of H6 is not on the die. It's on the
>  	 * co-packaged AC200 chip instead.
> @@ -933,25 +922,11 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
>  	struct sunxi_priv_data *gmac = plat->bsp_priv;
>  	struct device_node *node = dev->of_node;
>  	int ret;
> -	u32 reg, val;
> -
> -	ret = regmap_field_read(gmac->regmap_field, &val);
> -	if (ret) {
> -		dev_err(dev, "Fail to read from regmap field.\n");
> -		return ret;
> -	}
> -
> -	reg = gmac->variant->default_syscon_value;
> -	if (reg != val)
> -		dev_warn(dev,
> -			 "Current syscon value is not the default %x (expect %x)\n",
> -			 val, reg);
> +	u32 reg = 0, val;

Ok, here is where you used to read the value and log a warning if it was
different from the expected?>
>  	if (gmac->variant->soc_has_internal_phy) {
>  		if (of_property_read_bool(node, "allwinner,leds-active-low"))
>  			reg |= H3_EPHY_LED_POL;
> -		else
> -			reg &= ~H3_EPHY_LED_POL;
>  
>  		/* Force EPHY xtal frequency to 24MHz. */
>  		reg |= H3_EPHY_CLK_SEL;
> @@ -965,11 +940,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
>  		 * address. No need to mask it again.
>  		 */
>  		reg |= ret << H3_EPHY_ADDR_SHIFT;
> -	} else {
> -		/* For SoCs without internal PHY the PHY selection bit should be
> -		 * set to 0 (external PHY).
> -		 */
> -		reg &= ~H3_EPHY_SELECT;

You used to clear this value here for SoC without internal PHY. This is
ok to remove since you are building up from zero so this is already
clear by default.

>  	}
>  
>  	if (!of_property_read_u32(node, "allwinner,tx-delay-ps", &val)) {
> @@ -980,8 +950,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
>  		val /= 100;
>  		dev_dbg(dev, "set tx-delay to %x\n", val);
>  		if (val <= gmac->variant->tx_delay_max) {
> -			reg &= ~(gmac->variant->tx_delay_max <<
> -				 SYSCON_ETXDC_SHIFT);
>  			reg |= (val << SYSCON_ETXDC_SHIFT);
>  		} else {
>  			dev_err(dev, "Invalid TX clock delay: %d\n",
> @@ -998,8 +966,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
>  		val /= 100;
>  		dev_dbg(dev, "set rx-delay to %x\n", val);
>  		if (val <= gmac->variant->rx_delay_max) {
> -			reg &= ~(gmac->variant->rx_delay_max <<
> -				 SYSCON_ERXDC_SHIFT);
>  			reg |= (val << SYSCON_ERXDC_SHIFT);
>  		} else {
>  			dev_err(dev, "Invalid RX clock delay: %d\n",
> @@ -1008,11 +974,6 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
>  		}
>  	}
>  
> -	/* Clear interface mode bits */
> -	reg &= ~(SYSCON_ETCS_MASK | SYSCON_EPIT);
> -	if (gmac->variant->support_rmii)
> -		reg &= ~SYSCON_RMII_EN;
> -
>  	switch (plat->mac_interface) {
>  	case PHY_INTERFACE_MODE_MII:
>  		/* default */
> @@ -1039,9 +1000,9 @@ static int sun8i_dwmac_set_syscon(struct device *dev,
>  
>  static void sun8i_dwmac_unset_syscon(struct sunxi_priv_data *gmac)
>  {
> -	u32 reg = gmac->variant->default_syscon_value;
> -
> -	regmap_field_write(gmac->regmap_field, reg);
> +	if (gmac->variant->soc_has_internal_phy)
> +		regmap_field_write(gmac->regmap_field,
> +				   (H3_EPHY_SHUTDOWN | H3_EPHY_SELECT));

But now instead, you set it only if you *do* have an internal PHY. Good.

>  }
>  
>  static void sun8i_dwmac_exit(struct platform_device *pdev, void *priv)


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Re: [PATCH net-next] net: stmmac: sun8i: drop unneeded default syscon value

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 25 Aug 2025 18:20:55 +0100 you wrote:
> For some odd reason we were very jealous about the value of the EMAC
> clock register from the syscon block, insisting on a reset value and
> only doing read-modify-write operations on that register, even though we
> pretty much know the register layout.
> This already led to a basically redundant entry for the H6, which only
> differs by that value. We seem to have the same situation with the new
> A523 SoC, which again is compatible to the A64, but has a different
> syscon reset value.
> 
> [...]

Here is the summary with links:
  - [net-next] net: stmmac: sun8i: drop unneeded default syscon value
    https://git.kernel.org/netdev/net-next/c/330355191a2d

You are awesome, thank you!
-- 
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