Subject: Re: [PATCH net-next 08/13] net: dsa: hellcreek: deny tc-taprio changes to per-tc max SDU

From: Kurt Kanzenbach <[email-masked]>
Date: Thu, 15 Sep 2022 08:15:54 +0200

On Wed Sep 14 2022, Vladimir Oltean wrote:
> On Wed, Sep 14, 2022 at 08:13:53PM +0200, Kurt Kanzenbach wrote:
>> I'd rather like to see that feature implemented :-). Something like below.
>> 
>> From 3d44683979bf50960125fa3005b1142af61525c7 Mon Sep 17 00:00:00 2001
>> From: Kurt Kanzenbach <[email-masked]>
>> Date: Wed, 14 Sep 2022 19:51:40 +0200
>> Subject: [PATCH] net: dsa: hellcreek: Offload per-tc max SDU from tc-taprio
>> 
>> Add support for configuring the max SDU per priority and per port. If not
>> specified, keep the default.
>> 
>> Signed-off-by: Kurt Kanzenbach <[email-masked]>
>> ---
>
> Nice :) Do you also want the iproute2 patch, so you can test it?

Sure. I see you posted that patch already.

>
>>  drivers/net/dsa/hirschmann/hellcreek.c | 61 +++++++++++++++++++++++---
>>  drivers/net/dsa/hirschmann/hellcreek.h |  7 +++
>>  2 files changed, 61 insertions(+), 7 deletions(-)
>> 
>> diff --git a/drivers/net/dsa/hirschmann/hellcreek.c b/drivers/net/dsa/hirschmann/hellcreek.c
>> index 5ceee71d9a25..1b22710e1641 100644
>> --- a/drivers/net/dsa/hirschmann/hellcreek.c
>> +++ b/drivers/net/dsa/hirschmann/hellcreek.c
>> @@ -128,6 +128,16 @@ static void hellcreek_select_prio(struct hellcreek *hellcreek, int prio)
>>  	hellcreek_write(hellcreek, val, HR_PSEL);
>>  }
>>  
>> +static void hellcreek_select_port_prio(struct hellcreek *hellcreek, int port,
>> +				       int prio)
>> +{
>> +	u16 val = port << HR_PSEL_PTWSEL_SHIFT;
>> +
>> +	val |= prio << HR_PSEL_PRTCWSEL_SHIFT;
>> +
>> +	hellcreek_write(hellcreek, val, HR_PSEL);
>> +}
>> +
>>  static void hellcreek_select_counter(struct hellcreek *hellcreek, int counter)
>>  {
>>  	u16 val = counter << HR_CSEL_SHIFT;
>> @@ -1537,6 +1547,42 @@ hellcreek_port_prechangeupper(struct dsa_switch *ds, int port,
>>  	return ret;
>>  }
>>  
>> +static void hellcreek_setup_maxsdu(struct hellcreek *hellcreek, int port,
>> +				   const struct tc_taprio_qopt_offload *schedule)
>> +{
>> +	int tc;
>> +
>> +	for (tc = 0; tc < 8; ++tc) {
>> +		u16 val;
>> +
>> +		if (!schedule->max_sdu[tc])
>> +			continue;
>> +
>> +		hellcreek_select_port_prio(hellcreek, port, tc);
>> +
>> +		val = (schedule->max_sdu[tc] & HR_PTPRTCCFG_MAXSDU_MASK)
>> +			<< HR_PTPRTCCFG_MAXSDU_SHIFT;
>> +
>> +		hellcreek_write(hellcreek, val, HR_PTPRTCCFG);
>
> So the maxSDU hardware register tracks exactly the L2 payload size, like
> the software variable does, or does it include the Ethernet header size
> and/or FCS?

This is something I'm not sure about. I'll ask the HW engineer when he's
back from vacation.

Thanks,
Kurt