Re: [PATCH v2 0/4] s32g: Use a syscon for GPR

[Frank Li <Frank.li@nxp.com>]

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
>