netdev - Re: [PATCH] sh_eth: unmap DMA buffers when freeing rings

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Date:   Mon, 17 Apr 2017 15:45:47 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     netdev@...r.kernel.org
Cc:     linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] sh_eth: unmap DMA buffers when freeing rings

Hello!

On 04/17/2017 11:57 AM, Sergei Shtylyov wrote:

>> WARNING: CPU: 0 PID: 1445 at lib/dma-debug.c:519 add_dma_entry+0xe0/0x12c
>> DMA-API: exceeded 7 overlapping mappings of cacheline 0x01b2974d
>>
>> to be  printed after repeated initialization of the Ether device, e.g.
>> suspend/resume or 'ifconfig' up/down. This is because DMA buffers mapped
>> using dma_map_single() in sh_eth_ring_format() and sh_eth_start_xmit() are
>> never unmapped. Resolve this problem by unmapping the buffers when freeing
>> the descriptor  rings;  in order  to do it right, we'd have to add an extra
>> parameter to sh_eth_txfree() (we rename this function to sh_eth_tx_free(),
>> while at it).
>>
>> Based on the commit a47b70ea86bd ("ravb: unmap descriptors when freeing
>> rings").
>>
>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
>>
>> ---
>>  drivers/net/ethernet/renesas/sh_eth.c |  122
>> ++++++++++++++++++----------------
>>  1 file changed, 67 insertions(+), 55 deletions(-)
>>
>> Index: net/drivers/net/ethernet/renesas/sh_eth.c
>> ===================================================================
>> --- net.orig/drivers/net/ethernet/renesas/sh_eth.c
>> +++ net/drivers/net/ethernet/renesas/sh_eth.c
>> @@ -1127,12 +1127,70 @@ static struct mdiobb_ops bb_ops = {
>>      .get_mdio_data = sh_get_mdio,
>>  };
>>
>> +/* free Tx skb function */
>> +static int sh_eth_tx_free(struct net_device *ndev, bool sent_only)
>> +{
>> +    struct sh_eth_private *mdp = netdev_priv(ndev);
>> +    struct sh_eth_txdesc *txdesc;
>> +    int free_num = 0;
>> +    int entry;
>> +    bool sent;
>> +
>> +    for (; mdp->cur_tx - mdp->dirty_tx > 0; mdp->dirty_tx++) {
>> +        entry = mdp->dirty_tx % mdp->num_tx_ring;
>> +        txdesc = &mdp->tx_ring[entry];
>> +        sent = txdesc->status & cpu_to_le32(TD_TACT);
>
>    Oops, forgot to reverse the condition here. Which means I haven't goved in

    s/goved in/given it/. :-)

> enough testing... :-/

    TX statistics remained all 0s with this patch...

>> +        if (sent_only && !sent)
>> +            break;
[...]

MBR, Sergei