Re: [PATCH net-next 09/16] net: mdio: Add Synopsys DW XPCS management interface support

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi Serge,

On Tue,  5 Dec 2023 13:35:30 +0300
Serge Semin <fancer.lancer@gmail.com> wrote:

> Synopsys DesignWare XPCS IP-core can be synthesized with the device CSRs
> being accessible over MCI or APB3 interface instead of the MDIO bus (see
> the CSR_INTERFACE HDL parameter). Thus all the PCS registers can be just
> memory mapped and be a subject of standard MMIO operations of course
> taking into account the way the Clause C45 CSRs mapping is defined. This
> commit is about adding a device driver for the DW XPCS Management
> Interface platform device and registering it in the framework of the
> kernel MDIO subsystem.
> 
> DW XPCS platform device is supposed to be described by the respective
> compatible string "snps,dw-xpcs-mi", CSRs memory space and optional
> peripheral bus clock source. Note depending on the INDIRECT_ACCESS DW XPCS
> IP-core synthesize parameter the memory-mapped reg-space can be
> represented as either directly or indirectly mapped Clause 45 space. In
> the former case the particular address is determined based on the MMD
> device and the registers offset (5 + 16 bits all together) within the
> device reg-space. In the later case there is only 256 lower address bits
> are utilized for the registers mapping. The upper bits are supposed to be
> written into the respective viewport CSR in order to reach the entire C45
> space.

Too bad the mdio-regmap driver can't be re-used here, it would deal
with reg width for you, for example. I guess the main reason would be
the direct vs indirect accesses ?

I do have a comment tough :

[...]

> +static inline ptrdiff_t dw_xpcs_mmio_addr_format(int dev, int reg)
> +{
> +	return FIELD_PREP(0x1f0000, dev) | FIELD_PREP(0xffff, reg);
> +}
> +
> +static inline u16 dw_xpcs_mmio_addr_page(ptrdiff_t csr)
> +{
> +	return FIELD_GET(0x1fff00, csr);
> +}
> +
> +static inline ptrdiff_t dw_xpcs_mmio_addr_offset(ptrdiff_t csr)
> +{
> +	return FIELD_GET(0xff, csr);
> +}

You shouldn't use inline in C files, only in headers.

Maxime