linux-kernel - Re: [RFC 06/19] staging: qlge: disable flow control by default

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Message-ID: <20210624113353.mdcalrw77d4he4j5@Rk>
Date:   Thu, 24 Jun 2021 19:33:53 +0800
From:   Coiby Xu <coiby.xu@...il.com>
To:     Benjamin Poirier <benjamin.poirier@...il.com>
Cc:     linux-staging@...ts.linux.dev, netdev@...r.kernel.org,
        Shung-Hsi Yu <shung-hsi.yu@...e.com>,
        Manish Chopra <manishc@...vell.com>,
        "supporter:QLOGIC QLGE 10Gb ETHERNET DRIVER" 
        <GR-Linux-NIC-Dev@...vell.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 06/19] staging: qlge: disable flow control by default

On Tue, Jun 22, 2021 at 04:49:51PM +0900, Benjamin Poirier wrote:
>On 2021-06-21 21:48 +0800, Coiby Xu wrote:
>> According to the TODO item,
>> > * the flow control implementation in firmware is buggy (sends a flood of pause
>> >   frames, resets the link, device and driver buffer queues become
>> >   desynchronized), disable it by default
>>
>> Currently, qlge_mpi_port_cfg_work calls qlge_mb_get_port_cfg which gets
>> the link config from the firmware and saves it to qdev->link_config. By
>> default, flow control is enabled. This commit writes the
>> save the pause parameter of qdev->link_config and don't let it
>> overwritten by link settings of current port. Since qdev->link_config=0
>> when qdev is initialized, this could disable flow control by default and
>> the pause parameter value could also survive MPI resetting,
>>     $ ethtool -a enp94s0f0
>>     Pause parameters for enp94s0f0:
>>     Autonegotiate:  off
>>     RX:             off
>>     TX:             off
>>
>> The follow control can be enabled manually,
>>
>>     $ ethtool -A enp94s0f0 rx on tx on
>>     $ ethtool -a enp94s0f0
>>     Pause parameters for enp94s0f0:
>>     Autonegotiate:  off
>>     RX:             on
>>     TX:             on
>>
>> Signed-off-by: Coiby Xu <coiby.xu@...il.com>
>> ---
>>  drivers/staging/qlge/TODO       |  3 ---
>>  drivers/staging/qlge/qlge_mpi.c | 11 ++++++++++-
>>  2 files changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/staging/qlge/TODO b/drivers/staging/qlge/TODO
>> index b7a60425fcd2..8c84160b5993 100644
>> --- a/drivers/staging/qlge/TODO
>> +++ b/drivers/staging/qlge/TODO
>> @@ -4,9 +4,6 @@
>>    ql_build_rx_skb(). That function is now used exclusively to handle packets
>>    that underwent header splitting but it still contains code to handle non
>>    split cases.
>> -* the flow control implementation in firmware is buggy (sends a flood of pause
>> -  frames, resets the link, device and driver buffer queues become
>> -  desynchronized), disable it by default
>>  * some structures are initialized redundantly (ex. memset 0 after
>>    alloc_etherdev())
>>  * the driver has a habit of using runtime checks where compile time checks are
>> diff --git a/drivers/staging/qlge/qlge_mpi.c b/drivers/staging/qlge/qlge_mpi.c
>> index 2630ebf50341..0f1c7da80413 100644
>> --- a/drivers/staging/qlge/qlge_mpi.c
>> +++ b/drivers/staging/qlge/qlge_mpi.c
>> @@ -806,6 +806,7 @@ int qlge_mb_get_port_cfg(struct qlge_adapter *qdev)
>>  {
>>  	struct mbox_params mbc;
>>  	struct mbox_params *mbcp = &mbc;
>> +	u32 saved_pause_link_config = 0;
>
>Initialization is not needed given the code below, 

Thanks for the spotting this issue!

> in fact the
>declaration can be moved to the block below.

I thought I need to put the declaration in the beginning of the
function. But it seems Linux kernel coding style doesn't require it.
I'll move it to the else block below then.

>
>>  	int status = 0;
>>
>>  	memset(mbcp, 0, sizeof(struct mbox_params));
>> @@ -826,7 +827,15 @@ int qlge_mb_get_port_cfg(struct qlge_adapter *qdev)
>>  	} else	{
>>  		netif_printk(qdev, drv, KERN_DEBUG, qdev->ndev,
>>  			     "Passed Get Port Configuration.\n");
>> -		qdev->link_config = mbcp->mbox_out[1];
>> +		/*
>> +		 * Don't let the pause parameter be overwritten by
>> +		 *
>> +		 * In this way, follow control can be disabled by default
>> +		 * and the setting could also survive the MPI reset
>> +		 */
>
>It seems this comment is incomplete. Also, it's "flow control", not
>"follow control".

Ah, yes. I should state it as "Don't let the pause parameter be 
overwritten by be overwritten by the firmware.". And thanks for
correcting the typo.
>
>> +		saved_pause_link_config = qdev->link_config & CFG_PAUSE_STD;
>> +		qdev->link_config = ~CFG_PAUSE_STD & mbcp->mbox_out[1];
>> +		qdev->link_config |= saved_pause_link_config;
>>  		qdev->max_frame_size = mbcp->mbox_out[2];
>>  	}
>>  	return status;
>> --
>> 2.32.0
>>

-- 
Best regards,
Coiby