linux-kernel - Re: [PATCH] tg3: Add param `short_preamble` to enable MDIO traffic to external PHYs

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Message-ID: <3b36a977-426f-4f5a-9a1f-989a95a55a2a@molgen.mpg.de>
Date: Fri, 2 Aug 2024 22:55:45 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Michael Chan <michael.chan@...adcom.com>
Cc: Pavan Chebbi <pavan.chebbi@...adcom.com>,
 Michael Chan <mchan@...adcom.com>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Roy Lee <roy_lee@...ton.com>,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Saikrishna Arcot <sarcot@...rosoft.com>, Guohan Lu <lguohan@...il.com>
Subject: Re: [PATCH] tg3: Add param `short_preamble` to enable MDIO traffic to
 external PHYs

[Cc: +SONiC Linux kernel maintainers, cf patch submission [1]]

Dear Michael,

Thank you for the quick reply.

Am 02.08.24 um 21:51 schrieb Michael Chan:
> On Fri, Aug 2, 2024 at 3:05 AM Paul Menzel wrote:
> 
>> diff --git a/drivers/net/ethernet/broadcom/tg3.c b/drivers/net/ethernet/broadcom/tg3.c
>> index 0ec5f01551f9..9b4ab201fd9a 100644
>> --- a/drivers/net/ethernet/broadcom/tg3.c
>> +++ b/drivers/net/ethernet/broadcom/tg3.c
>> @@ -233,6 +233,10 @@ static int tg3_debug = -1; /* -1 == use TG3_DEF_MSG_ENABLE as value */
>>   module_param(tg3_debug, int, 0);
>>   MODULE_PARM_DESC(tg3_debug, "Tigon3 bitmapped debugging message enable value");
>>
>> +static int short_preamble = 0;
>> +module_param(short_preamble, int, 0);
>> +MODULE_PARM_DESC(short_preamble, "Enable short preamble.");
>> +
> 
> Module parameters are generally not accepted.  If this is something
> other devices can potentially use, it's better to use a more common
> interface.

I saw the patch in the SONiC repository and took a shot at upstreaming 
it. `tg.h` defines the macro:

     #define  MAC_MI_MODE_SHORT_PREAMBLE  0x00000002

Any idea how this should be used? Can it be enabled unconditionally? I 
do not even have the datasheet.

Kind regards,

Paul

[1]: 
https://lore.kernel.org/netdev/20240802100448.10745-1-pmenzel@molgen.mpg.de/