Re: [PATCH dev-4.7 2/2] net/faraday: Clear stale interrupts

[Joel Stanley <joel@jms.id.au>]

On Thu, 2016-07-28 at 11:04 +1000, Gavin Shan wrote:
> There is stale interrupt (PHYSTS_CHG in ISR, bit#6 in 0x0) from
> the bootloader (uboot) when enabling the MAC. The stale interrupts
> aren't part of kernel and should be cleared.
> 
> This clears the stale interrupts in ISR (0x0) when enabling the MAC.

Thanks Gavin. A question below.

> 
> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
> ---
>  drivers/net/ethernet/faraday/ftgmac100.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/faraday/ftgmac100.c
> b/drivers/net/ethernet/faraday/ftgmac100.c
> index f00911a..fc2852f 100644
> --- a/drivers/net/ethernet/faraday/ftgmac100.c
> +++ b/drivers/net/ethernet/faraday/ftgmac100.c
> @@ -1119,6 +1119,7 @@ static int ftgmac100_open(struct net_device
> *netdev)
>  {
>  	struct ftgmac100 *priv = netdev_priv(netdev);
>  	struct phy_device *phydev = netdev->phydev;
> +	unsigned int status;
>  	int err;
>  
>  	err = ftgmac100_alloc_buffers(priv);
> @@ -1145,6 +1146,10 @@ static int ftgmac100_open(struct net_device
> *netdev)
>  	ftgmac100_init_hw(priv);
>  	ftgmac100_start_hw(priv, priv->use_ncsi ? 100 : 10);
>  
> +	/* Clear stale interrupts */
> +	status = ioread32(priv->base + FTGMAC100_OFFSET_ISR);
> +	iowrite32(status, priv->base + FTGMAC100_OFFSET_ISR);

By the time we get down here we've called ftgmac100_reset_hw. This has
the following:

/* NOTE: reset clears all registers */
iowrite32(FTGMAC100_MACCR_SW_RST, priv->base + FTGMAC100_OFFSET_MACCR); 

We are seeing that it does not actually clear all the registers?

Secondly, if we're seeing stale interrupts is there a risk that they
will fire again between now and the call below where we
set FTGMAC100_OFFSET_IER?

Should we be masking them all off, clearing the stale ones, and then
re-enabling them?

Cheers,

Joel


> +
>  	if (phydev)
>  		phy_start(phydev);
>  	else if (priv->use_ncsi)