On 3/24/2021 1:13 PM, Vladimir Oltean wrote:
> Hi Martin,
>
> On Wed, Mar 24, 2021 at 09:04:16PM +0100, Martin Blumenstingl wrote:
>> Hello,
>>
>> the PMAC (Ethernet MAC) IP built into the Lantiq xRX200 SoCs has
>> support for multiple (TX) queues.
>> This MAC is connected to the SoC's built-in switch IP (called GSWIP).
>>
>> Right now the lantiq_xrx200 driver only uses one TX and one RX queue.
>> The vendor driver (which mixes DSA/switch and MAC functionality in one
>> driver) uses the following approach:
>> - eth0 ("lan") uses the first TX queue
>> - eth1 ("wan") uses the second TX queue
>>
>> With the current (mainline) lantiq_xrx200 driver some users are able
>> to fill up the first (and only) queue.
>> This is why I am thinking about adding support for the second queue to
>> the lantiq_xrx200 driver.
>>
>> My main question is: how do I do it properly?
>> Initializing the second TX queue seems simple (calling
>> netif_tx_napi_add for a second time).
>> But how do I choose the "right" TX queue in xrx200_start_xmit then?
If you use DSA you will have a DSA slave network device which will be
calling into dev_queue_xmit() into the DSA master which will be the
xrx200 driver, so it's fairly simple for you to implement a queue
selection within the xrx200 tagger for instance.
You can take a look at how net/dsa/tag_brcm.c and
drivers/net/ethernet/broadcom/bcmsysport.c work as far as mapping queues
from the DSA slave network device queue/port number into a queue number
for the DSA master.
--
Florian
