netdev - Re: [RFC PATCH 4/5] net: macb: Add support for suspend/resume with full power down

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Message-ID: <585eabe8-aae4-cfd3-01aa-bad17197a28d@microchip.com>
Date:   Thu, 3 May 2018 15:23:06 +0300
From:   Claudiu Beznea <Claudiu.Beznea@...rochip.com>
To:     Harini Katakam <harinik@...inx.com>
CC:     Nicolas Ferre <nicolas.ferre@...el.com>,
        David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <michals@...inx.com>,
        <appanad@...inx.com>
Subject: Re: [RFC PATCH 4/5] net: macb: Add support for suspend/resume with
 full power down



On 03.05.2018 14:20, Harini Katakam wrote:
> Hi Claudiu,
> 
> On Thu, May 3, 2018 at 3:39 PM, Claudiu Beznea
> <Claudiu.Beznea@...rochip.com> wrote:
>>
>>
>> On 22.03.2018 15:51, harinikatakamlinux@...il.com wrote:
>>> From: Harini Katakam <harinik@...inx.com>
>>>
>>> When macb device is suspended and system is powered down, the clocks
>>> are removed and hence macb should be closed gracefully and restored
>>> upon resume.
>>
>> Is this a power saving mode which shut down the core?
> 
> The Ethernet IP is suspended and a majority of the SoC is shut down, yes.
> 
> <snip>
>>> +             netif_device_detach(netdev);
>>> +     } else {
>>> +             netif_device_detach(netdev);
>>> +             for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue)
>>> +                     napi_disable(&queue->napi);
>>> +             phy_stop(netdev->phydev);
>>> +             phy_suspend(netdev->phydev);
>>> +             spin_lock_irqsave(&bp->lock, flags);
>>> +             macb_reset_hw(bp);
>>> +             spin_unlock_irqrestore(&bp->lock, flags);
>>
>> Wouldn't be simple to just call macb_close() here?
> 
> <snip>
>>
>> Wouln't be simpler to call macb_open() here?
> 
> No, I think that would be excessive for suspend. This does just
> enough to put the IP into suspend and cut off clocks.
> For ex., the RX and TX buffers are not freed and allocated again
> in this cycle, just the buffer descriptors.
> 

For me looks simpler to just call macb_close()/macb_open() in suspend/resume
hooks. Maybe this doesn't fit to your needs... But most of the code you
added in suspend/resume hooks is already present in macb_open()/macb_close(),
except the TX/RX buffers alloc/free.

SAMA5D2 also uses this IP. SAMA5d2 has a power saving mode where core power is cut
off (including this IP). We are using macb_open()/macb_close() + restoring all
few other registers after this (by calling macb_set_rx_mode() and a variant of
macb_set_features() and few other registers). This is not yet mainlined. I was
intending to send soon a version.

Thank you,
Claudiu

> Regards,
> Harini
>