The s32g devices have a GPR register region which holds a number of
miscellaneous registers.  Currently only the stmmac/dwmac-s32.c uses
anything from there and we just add a line to the device tree to
access that GMAC_0_CTRL_STS register:

                        reg = <0x4033c000 0x2000>, /* gmac IP */
                              <0x4007c004 0x4>;    /* GMAC_0_CTRL_STS */

We still have to maintain backwards compatibility to this format,
of course, but it would be better to access these through a syscon.
First of all, putting all the registers together is more organized
and shows how the hardware actually is implemented.  Secondly, in
some versions of this chipset those registers can only be accessed
via SCMI, if the registers aren't grouped together each driver will
have to create a whole lot of if then statements to access it via
IOMEM or via SCMI, where if we use a syscon interface we can write
a driver to handle that quite transparently without modifying each
individual driver which reads or writes to one of these registers.
That code is out of tree for now, but eventually we'll want to
support this.

Changed since v1:
* Add imx@lists.linux.dev to the CC list.
* Fix forward porting bug.  s/PHY_INTF_SEL_RGMII/S32_PHY_INTF_SEL_RGMII/
* Use the correct SoC names nxp,s32g2-gpr and nxp,s32g3-gpr instead of
  nxp,s32g-gpr which is the SoC family.
* Fix the phandle name by adding the vendor prefix
* Fix the documentation for the phandle
* Remove #address-cells and #size-cells from the syscon block

Here is the whole list of registers in the GPR region

Starting from 0x4007C000

0  Software-Triggered Faults (SW_NCF)
4  GMAC Control (GMAC_0_CTRL_STS)
28 CMU Status 1 (CMU_STATUS_REG1)
2C CMUs Status 2 (CMU_STATUS_REG2)
30 FCCU EOUT Override Clear (FCCU_EOUT_OVERRIDE_CLEAR_REG)
38 SRC POR Control (SRC_POR_CTRL_REG)
54 GPR21 (GPR21)
5C GPR23 (GPR23)
60 GPR24 Register (GPR24)
CC Debug Control (DEBUG_CONTROL)
F0 Timestamp Control (TIMESTAMP_CONTROL_REGISTER)
F4 FlexRay OS Tick Input Select (FLEXRAY_OS_TICK_INPUT_SELECT_REG)
FC GPR63 Register (GPR63)

Starting from 0x4007CA00

0  Coherency Enable for PFE Ports (PFE_COH_EN)
4  PFE EMAC Interface Mode (PFE_EMACX_INTF_SEL)
20 PFE EMACX Power Control (PFE_PWR_CTRL)
28 Error Injection on Cortex-M7 AHB and AXI Pipe (CM7_TCM_AHB_SLICE)
2C Error Injection AHBP Gasket Cortex-M7 (ERROR_INJECTION_AHBP_GASKET_CM7)
40 LLCE Subsystem Status (LLCE_STAT)
44 LLCE Power Control (LLCE_CTRL)
48 DDR Urgent Control (DDR_URGENT_CTRL)
4C FTM Global Load Control (FLXTIM_CTRL)
50 FTM LDOK Status (FLXTIM_STAT)
54 Top CMU Status (CMU_STAT)
58 Accelerator NoC No Pending Trans Status (NOC_NOPEND_TRANS)
90 SerDes RD/WD Toggle Control (PCIE_TOGGLE)
94 SerDes Toggle Done Status (PCIE_TOGGLEDONE_STAT)
E0 Generic Control 0 (GENCTRL0)
E4 Generic Control 1 (GENCTRL1)
F0 Generic Status 0 (GENSTAT0)
FC Cortex-M7 AXI Parity Error and AHBP Gasket Error Alarm (CM7_AXI_AHBP_GASKET_ERROR_ALARM)

Starting from 4007C800

4  GPR01 Register (GPR01)
30 GPR12 Register (GPR12)
58 GPR22 Register (GPR22)
70 GPR28 Register (GPR28)
74 GPR29 Register (GPR29)

Starting from 4007CB00

4 WKUP Pad Pullup/Pulldown Select (WKUP_PUS)

Dan Carpenter (4):
  net: stmmac: s32: use a syscon for S32_PHY_INTF_SEL_RGMII
  dt-bindings: mfd: syscon: Document the GPR syscon for the NXP S32 SoCs
  dt-bindings: net: nxp,s32-dwmac: Use the GPR syscon
  dts: s32g: Add GPR syscon region

 .../devicetree/bindings/mfd/syscon.yaml       |  4 ++++
 .../bindings/net/nxp,s32-dwmac.yaml           | 10 ++++++++
 arch/arm64/boot/dts/freescale/s32g2.dtsi      |  6 +++++
 arch/arm64/boot/dts/freescale/s32g3.dtsi      |  6 +++++
 .../net/ethernet/stmicro/stmmac/dwmac-s32.c   | 23 +++++++++++++++----
 5 files changed, 44 insertions(+), 5 deletions(-)

-- 
2.51.0

On Mon, Dec 15, 2025 at 05:41:43PM +0300, Dan Carpenter wrote:
> The s32g devices have a GPR register region which holds a number of
> miscellaneous registers.  Currently only the stmmac/dwmac-s32.c uses
> anything from there and we just add a line to the device tree to
> access that GMAC_0_CTRL_STS register:
>
>                         reg = <0x4033c000 0x2000>, /* gmac IP */
>                               <0x4007c004 0x4>;    /* GMAC_0_CTRL_STS */
>
> We still have to maintain backwards compatibility to this format,
> of course, but it would be better to access these through a syscon.
> First of all, putting all the registers together is more organized
> and shows how the hardware actually is implemented.  Secondly, in
> some versions of this chipset those registers can only be accessed
> via SCMI, if the registers aren't grouped together each driver will
> have to create a whole lot of if then statements to access it via
> IOMEM or via SCMI,

Does SCMI work as regmap? syscon look likes simple, but missed abstract
in overall.

You still use regmap by use MMIO. /* GMAC_0_CTRL_STS */

regmap = devm_regmap_init_mmio(dev, sts_offset, &regmap_config);

So all code can use regmap function without if-then statements if SCMI work
as regmap.

Frank


>where if we use a syscon interface we can write
> a driver to handle that quite transparently without modifying each
> individual driver which reads or writes to one of these registers.
> That code is out of tree for now, but eventually we'll want to
> support this.
>
> Changed since v1:
> * Add imx@lists.linux.dev to the CC list.
> * Fix forward porting bug.  s/PHY_INTF_SEL_RGMII/S32_PHY_INTF_SEL_RGMII/
> * Use the correct SoC names nxp,s32g2-gpr and nxp,s32g3-gpr instead of
>   nxp,s32g-gpr which is the SoC family.
> * Fix the phandle name by adding the vendor prefix
> * Fix the documentation for the phandle
> * Remove #address-cells and #size-cells from the syscon block
>
> Here is the whole list of registers in the GPR region
>
> Starting from 0x4007C000
>
> 0  Software-Triggered Faults (SW_NCF)
> 4  GMAC Control (GMAC_0_CTRL_STS)
> 28 CMU Status 1 (CMU_STATUS_REG1)
> 2C CMUs Status 2 (CMU_STATUS_REG2)
> 30 FCCU EOUT Override Clear (FCCU_EOUT_OVERRIDE_CLEAR_REG)
> 38 SRC POR Control (SRC_POR_CTRL_REG)
> 54 GPR21 (GPR21)
> 5C GPR23 (GPR23)
> 60 GPR24 Register (GPR24)
> CC Debug Control (DEBUG_CONTROL)
> F0 Timestamp Control (TIMESTAMP_CONTROL_REGISTER)
> F4 FlexRay OS Tick Input Select (FLEXRAY_OS_TICK_INPUT_SELECT_REG)
> FC GPR63 Register (GPR63)
>
> Starting from 0x4007CA00
>
> 0  Coherency Enable for PFE Ports (PFE_COH_EN)
> 4  PFE EMAC Interface Mode (PFE_EMACX_INTF_SEL)
> 20 PFE EMACX Power Control (PFE_PWR_CTRL)
> 28 Error Injection on Cortex-M7 AHB and AXI Pipe (CM7_TCM_AHB_SLICE)
> 2C Error Injection AHBP Gasket Cortex-M7 (ERROR_INJECTION_AHBP_GASKET_CM7)
> 40 LLCE Subsystem Status (LLCE_STAT)
> 44 LLCE Power Control (LLCE_CTRL)
> 48 DDR Urgent Control (DDR_URGENT_CTRL)
> 4C FTM Global Load Control (FLXTIM_CTRL)
> 50 FTM LDOK Status (FLXTIM_STAT)
> 54 Top CMU Status (CMU_STAT)
> 58 Accelerator NoC No Pending Trans Status (NOC_NOPEND_TRANS)
> 90 SerDes RD/WD Toggle Control (PCIE_TOGGLE)
> 94 SerDes Toggle Done Status (PCIE_TOGGLEDONE_STAT)
> E0 Generic Control 0 (GENCTRL0)
> E4 Generic Control 1 (GENCTRL1)
> F0 Generic Status 0 (GENSTAT0)
> FC Cortex-M7 AXI Parity Error and AHBP Gasket Error Alarm (CM7_AXI_AHBP_GASKET_ERROR_ALARM)
>
> Starting from 4007C800
>
> 4  GPR01 Register (GPR01)
> 30 GPR12 Register (GPR12)
> 58 GPR22 Register (GPR22)
> 70 GPR28 Register (GPR28)
> 74 GPR29 Register (GPR29)
>
> Starting from 4007CB00
>
> 4 WKUP Pad Pullup/Pulldown Select (WKUP_PUS)
>
> Dan Carpenter (4):
>   net: stmmac: s32: use a syscon for S32_PHY_INTF_SEL_RGMII
>   dt-bindings: mfd: syscon: Document the GPR syscon for the NXP S32 SoCs
>   dt-bindings: net: nxp,s32-dwmac: Use the GPR syscon
>   dts: s32g: Add GPR syscon region
>
>  .../devicetree/bindings/mfd/syscon.yaml       |  4 ++++
>  .../bindings/net/nxp,s32-dwmac.yaml           | 10 ++++++++
>  arch/arm64/boot/dts/freescale/s32g2.dtsi      |  6 +++++
>  arch/arm64/boot/dts/freescale/s32g3.dtsi      |  6 +++++
>  .../net/ethernet/stmicro/stmmac/dwmac-s32.c   | 23 +++++++++++++++----
>  5 files changed, 44 insertions(+), 5 deletions(-)
>
> --
> 2.51.0
>