netdev - Re: [PATCH net-next v3 08/19] net: ravb: Move the IRQs get and request in the probe function

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Date: Wed, 10 Jan 2024 13:55:18 +0200
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Sergey Shtylyov <s.shtylyov@....ru>, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 richardcochran@...il.com, p.zabel@...gutronix.de,
 yoshihiro.shimoda.uh@...esas.com, wsa+renesas@...g-engineering.com
Cc: netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
 linux-kernel@...r.kernel.org, geert+renesas@...der.be,
 Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH net-next v3 08/19] net: ravb: Move the IRQs get and
 request in the probe function



On 09.01.2024 22:47, Sergey Shtylyov wrote:
> On 1/8/24 11:58 AM, claudiu beznea wrote:
> 
> [...]
>>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>>
>>>> The runtime PM implementation will disable clocks at the end of
>>>> ravb_probe(). As some IP variants switch to reset mode as a result of
>>>> setting module standby through clock disable APIs, to implement runtime PM
>>>> the resource parsing and requesting are moved in the probe function and IP
>>>> settings are moved in the open function. This is done because at the end of
>>>> the probe some IP variants will switch anyway to reset mode and the
>>>> registers content is lost. Also keeping only register specific operations
>>>> in the ravb_open()/ravb_close() functions will make them faster.
>>>>
>>>> Commit moves IRQ requests to ravb_probe() to have all the IRQs ready when
>>>> the interface is open. As now IRQs gets and requests are in a single place
>>>> there is no need to keep intermediary data (like ravb_rx_irqs[] and
>>>> ravb_tx_irqs[] arrays or IRQs in struct ravb_private).
>>>
>>>    There's one thing that you probably didn't take into account: after
>>> you call request_irq(), you should be able to handle your IRQ as it's
>>> automatically unmasked, unless you pass IRQF_NO_AUTOEN to request_irq().
>>> Your device may be held i reset or even powered off but if you pass IRQF_SHARED to request_irq() (you do in a single IRQ config), you must
>>> be prepared to get your device's registers read (in order to ascertain
> 
>    And, at least on arm32, reading a powered off (or not clocked?) device's
> register causes an imprecise external abort exception -- which results in a
> kernel oops...
> 
>>> whether it's your IRQ or not). And you can't even pass IRQF_NO_AUTOEN
>>> along with IRQF_SHARED, according to my reading of the IRQ code...
>>
>> Good point!
>>
>>>> This is a preparatory change to add runtime PM support for all IP variants.
>>>
>>>   I don't readily see why this is necessary for the full-fledged RPM
>>> support...
>>
>> I tried to speed up the ravb_open()/ravb_close() but missed the IRQF_SHARED
> 
>    I doubt that optimizing ravb_{open,close}() is worth pursuing, frankly...
> 
>> IRQ. As there is only one IRQ requested w/ IRQF_SHARED, are you OK with
>> still keeping the rest of IRQs handled as proposed by this patch?
> 
>    I'm not, as this doesn't really seem necessary for your main goal.
> It's not clear in what state U-Boot leaves EtherAVB...

Ok. One other reason I did this is, as commit message states, to keep
resource parsing and allocation/freeing in probe/remove and hardware
settings in open/close.

Anyway, I'll revert all the changes IRQ related.

Thank you,
Claudiu Beznea

> 
> [...]
> 
> MBR, Sergey