Re: [PATCH v2 01/13] PCI: dwc: Add dw_pcie_clear_and_set_dword() for register bit manipulation

[Frank Li]

On Wed, Jun 18, 2025 at 11:21:00PM +0800, Hans Zhang wrote:
> DesignWare PCIe controller drivers implement register bit manipulation
> through explicit read-modify-write sequences. These patterns appear
> repeatedly across multiple drivers with minor variations, creating
> code duplication and maintenance overhead.
>
> Implement dw_pcie_clear_and_set_dword() helper to encapsulate atomic
> register modification. The function reads the current register value,
> clears specified bits, sets new bits, and writes back the result in
> a single operation. This abstraction hides bitwise manipulation details
> while ensuring consistent behavior across all usage sites.
>
> Centralizing this logic reduces future maintenance effort when modifying
> register access patterns and minimizes the risk of implementation
> divergence between drivers.
>
> Signed-off-by: Hans Zhang <18255117159@xxxxxxx>
> ---
>  drivers/pci/controller/dwc/pcie-designware.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-designware.h b/drivers/pci/controller/dwc/pcie-designware.h
> index ce9e18554e42..f401c144df0f 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.h
> +++ b/drivers/pci/controller/dwc/pcie-designware.h
> @@ -707,6 +707,17 @@ static inline void dw_pcie_ep_writel_dbi2(struct dw_pcie_ep *ep, u8 func_no,
>  	dw_pcie_ep_write_dbi2(ep, func_no, reg, 0x4, val);
>  }
>
> +static inline void dw_pcie_clear_and_set_dword(struct dw_pcie *pci, int pos,
> +					       u32 clear, u32 set)

Can align with regmap_update_bits() argumnet?

dw_pcie_update_dbi_bits()?

Frank

> +{
> +	u32 val;
> +
> +	val = dw_pcie_readl_dbi(pci, pos);
> +	val &= ~clear;
> +	val |= set;
> +	dw_pcie_writel_dbi(pci, pos, val);
> +}
> +
>  static inline void dw_pcie_dbi_ro_wr_en(struct dw_pcie *pci)
>  {
>  	u32 reg;
> --
> 2.25.1
>