Re: [PATCH net v4] net: pcs: rzn1-miic: Clear MIIC protection state before unprotect sequence

[Lad, Prabhakar]

On Thu, Sep 24, 2026 at 11:45 AM Yoshihisa Yamamoto
<yoshihisa.yamamoto.xn@xxxxxxxxxxx> wrote:
>
> On RZ/T2H and RZ/N1D MIIC, writing 0x0000 to the MIIC protection
> register clears the protection state machine.
>
> The initial protection state cannot be assumed to be constant,
> as it may be influenced by previous activity before the driver
> takes ownership of the hardware.
>
> Clear the protection state before issuing the unprotect sequence
> so that register access always starts from a known state, regardless
> of any previous activity.
>
> Fixes: 7dc54d3b8d91 ("net: pcs: add Renesas MII converter driver")
> Signed-off-by: Yoshihisa Yamamoto <yoshihisa.yamamoto.xn@xxxxxxxxxxx>
> ---
> V4:
> - Clarify commit message
> - Point Fixes tag to 7dc54d3b8d91, as the issue also affects RZ/N1D
>
> v3: https://lore.kernel.org/all/TYCPR01MB7481CE8351FDB2CDCA229955A4872@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> - Add Fixes tag
>
> v2: https://lore.kernel.org/all/TYCPR01MB748157ECB6B92D8E3FFD433BA4B82@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> - Fix indentation
>
> v1: https://lore.kernel.org/all/TYCPR01MB748139F059DF2459B9813416A4B92@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
>  drivers/net/pcs/pcs-rzn1-miic.c | 3 +++
>  1 file changed, 3 insertions(+)
>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

Cheers,
Prabhakar

> diff --git a/drivers/net/pcs/pcs-rzn1-miic.c b/drivers/net/pcs/pcs-rzn1-miic.c
> index 2b72fa98ddf1..279f709c889b 100644
> --- a/drivers/net/pcs/pcs-rzn1-miic.c
> +++ b/drivers/net/pcs/pcs-rzn1-miic.c
> @@ -270,6 +270,9 @@ static struct miic_port *phylink_pcs_to_miic_port(struct phylink_pcs *pcs)
>
>  static void miic_unlock_regs(struct miic *miic)
>  {
> +       /* Clear protection state */
> +       writel(0x0000, miic->base + MIIC_PRCMD);
> +
>         /* Unprotect register writes */
>         writel(0x00A5, miic->base + MIIC_PRCMD);
>         writel(0x0001, miic->base + MIIC_PRCMD);
> --
> 2.34.1
>