Re: [PATCH net] net: macb: take bp->lock around NCR read-modify-writes

[Nicolai Buchwitz]

Hi Théo

On 18.9.2026 21:59, Théo Lebrun wrote:
> NCR is read-modify-written from many contexts:
>
>  - macb_mac_link_down() clears RE|TE,
>  - macb_mac_link_up() sets RE|TE|PTPUNI,
>  - macb_hresp_error_task() clears then re-sets RE|TE,
>  - macb_start_xmit() / macb_tx_restart() / macb_tx_error_task() set
>    TSTART (already under bp->lock),
>  - macb_interrupt() might toggle RE (also under bp->lock).
>
> The first three risk concurrent RMW with anyone from the list as they
> don't grab bp->lock.

There is a fourth, in at91ether_interrupt():

     if (intstatus & MACB_BIT(RXUBR)) {
             ctl = macb_readl(bp, NCR);
             macb_writel(bp, NCR, ctl & ~MACB_BIT(RE));
             wmb();
             macb_writel(bp, NCR, ctl | MACB_BIT(RE));
     }

I guess you have skipped this as the emac variants using this are not 
SMP?

> [...]

Reviewed-by: Nicolai Buchwitz <nb@xxxxxxxxxxx>

Regards
Nicolai