Re: [PATCH net-next v1 01/14] net: phy: nxp-c45-tja11xx: fix the PTP interrupt enablig/disabling

[Andrew Lunn]

On Fri, Jun 16, 2023 at 04:53:10PM +0300, Radu Pirea (NXP OSS) wrote:
> .config_intr() handles only the link event interrupt and should
> disable/enable the PTP interrupt also.
> 
> It's safe to disable/enable the PTP irq even if the egress ts irq
> is disabled. This interrupt, the PTP one, acts as a global switch for all
> PTP irqs.
> 
> Fixes: 514def5dd339 ("phy: nxp-c45-tja11xx: add timestamping support")
> CC: stable@xxxxxxxxxxxxxxx # 5.15+
> Signed-off-by: Radu Pirea (NXP OSS) <radu-nicolae.pirea@xxxxxxxxxxx>

Please don't mix fixes and development work in one patchset. Please
post this to applying to net, not net-next.

>  static int nxp_c45_config_intr(struct phy_device *phydev)
>  {
> -	if (phydev->interrupts == PHY_INTERRUPT_ENABLED)
> +	/* The return value is ignored on purpose. It might be < 0.
> +	 * 0x807A register is not present on SJA1110 PHYs.
> +	 */
> +	if (phydev->interrupts == PHY_INTERRUPT_ENABLED) {
> +		phy_set_bits_mmd(phydev, MDIO_MMD_VEND1,
> +				 VEND1_PORT_FUNC_IRQ_EN, PTP_IRQS);
>  		return phy_set_bits_mmd(phydev, MDIO_MMD_VEND1,
>  					VEND1_PHY_IRQ_EN, PHY_IRQ_LINK_EVENT);

phy_set_bits_mmd() will not return an error if the register does not
exist. There is no such indication for MDIO. This is going to do a
read/modify/write. That read might get 0xffff, or random junk. And
then the write back will be successful. The only time
phy_read()/phy_write return error is when there is a problem within
the bus master, like its clock gets turned off and the transfer times
out.

So it is good to document you are accessing a register which might not
exist, but there is no need to ignore the return code.

       Andrew