Subject: Re: [PATCH] net: bcmgenet: fix increase rx_read_ptr

From: Florian Fainelli <[email-masked]>
Date: Tue, 07 Oct 2014 10:01:00 -0700

On 10/06/2014 11:40 PM, Jaedon Shin wrote:
> This patch fixes the previous commit b629be5c8399d7c423b92135eb43a86c924d1cbc ("net: bcmgenet: check harder for out of memory conditions").
> 
> The previous commit has a problem that gets invalid dma_length_status by increased rx_read_ptr. And it should be increased after all goto refill.

Good catch, I have some other GENET and SYSTEMPORT fixes for net that I
will submit shortly. Thank you!

>  
> 
>> On Oct 7, 2014, at 1:45 AM, Florian Fainelli <[email-masked]> wrote:
>>
>> On 10/05/2014 08:05 PM, Jaedon Shin wrote:
>>> The rx_read_ptr must increase after using it.
>>
>> Your commit message is too terse, you need to explain why you think the
>> current code is bad, and how your patch is fixing it.
>>
>> One possible thing that I see is that we might be off by one in how we
>> use the enet_cb versus how we read the HW packet descriptor.
>>
>>>
>>> Signed-off-by: Jaedon Shin <[email-masked]>
>>> ---
>>> drivers/net/ethernet/broadcom/genet/bcmgenet.c | 6 +++---
>>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
>>> index 5cc9cae..b47db5e 100644
>>> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
>>> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
>>> @@ -1282,9 +1282,6 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_priv *priv,
>>>
>>> 		rxpktprocessed++;
>>>
>>> -		priv->rx_read_ptr++;
>>> -		priv->rx_read_ptr &= (priv->num_rx_bds - 1);
>>> -
>>> 		/* We do not have a backing SKB, so we do not have a
>>> 		 * corresponding DMA mapping for this incoming packet since
>>> 		 * bcmgenet_rx_refill always either has both skb and mapping or
>>> @@ -1399,6 +1396,9 @@ refill:
>>> 		err = bcmgenet_rx_refill(priv, cb);
>>> 		if (err)
>>> 			netif_err(priv, rx_err, dev, "Rx refill failed\n");
>>> +
>>> +		priv->rx_read_ptr++;
>>> +		priv->rx_read_ptr &= (priv->num_rx_bds - 1);
>>> 	}
>>>
>>> 	return rxpktprocessed;
>>>
>>
>