netdev - Re: [PATCH net-next v2 09/21] net: ravb: Split GTI computation and set operations

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Message-ID: <154d6a86-d2d3-afae-a604-aa8fecb63f23@omp.ru>
Date: Tue, 19 Dec 2023 21:20:46 +0300
From: Sergey Shtylyov <s.shtylyov@....ru>
To: claudiu beznea <claudiu.beznea@...on.dev>, <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>,
	<geert+renesas@...der.be>
CC: <netdev@...r.kernel.org>, <linux-renesas-soc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Claudiu Beznea
	<claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH net-next v2 09/21] net: ravb: Split GTI computation and
 set operations

On 12/17/23 3:40 PM, claudiu beznea wrote:

[...]
>>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>
>>> ravb_set_gti() was computing the value of GTI based on the reference clock
>>> rate and then applied it to register. This was done on the driver's probe
>>> function. In order to implement runtime PM for all IP variants (as some IP
>>> variants switches to reset operation mode (and thus the register's content
>>
>>    Again, operating mode...
>>
>>> is lost) when module standby is configured through clock APIs) the GTI was
>>
>>    The GTI what? Setup?
>>
>>> split in 2 parts: one computing the value of the GTI register (done in the
>>> driver's probe function) and one applying the computed value to register
>>> (done in the driver's ndo_open API).
>>>
>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>> [...]
>>
>>> diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
>>> index e0f8276cffed..76202395b68d 100644
>>> --- a/drivers/net/ethernet/renesas/ravb.h
>>> +++ b/drivers/net/ethernet/renesas/ravb.h
>>> @@ -1106,6 +1106,8 @@ struct ravb_private {
>>>  
>>>  	const struct ravb_hw_info *info;
>>>  	struct reset_control *rstc;
>>> +
>>> +	uint64_t gti_tiv;
>>
>>    Please use the kernel type, u64; uint64_t is for userland, IIRC.
> 
> I just kept the initial type here.

   Oops, that type slipped in while I wasn't yet a reviewer. :-/

> Anyway, uint64_t should translate to u64 AFAICT.

   Yes.

> Looking at it again the field here is enough to be 32 bit as the register
> field is no longer than that. It is needed on 64 bits when checking the
> ranges in compute function.

   Indeed. The actual GTI.TIV field is even 28-bit wide only...

[...]
>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>> index d7f6e8ea8e79..5e01e03e1b43 100644
>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>> @@ -1750,6 +1750,51 @@ static int ravb_set_reset_mode(struct net_device *ndev)
>>>  	return error;
>>>  }
>>>  
>>> +static int ravb_set_gti(struct net_device *ndev)
>>> +{
>> [...]
>>> +	/* Request GTI loading */
>>> +	ravb_modify(ndev, GCCR, GCCR_LTI, GCCR_LTI);
>>> +
>>> +	/* Check completion status. */
>>> +	return ravb_wait(ndev, GCCR, GCCR_LTI, 0);
>>
>>    Is this really necessary?
> 
> I've just updated it to respect the manual specifications. Please let me
> know if you want me to drop it. For this series it should be harmless
> keeping it as it was previously (I will double check it).

   Looks like you'll have to frop the fix patch #2, so this ravb_wait()
call shouldn't be placed here as well...

>> [...]
>>> @@ -1767,6 +1812,10 @@ static int ravb_open(struct net_device *ndev)
>>>  		goto out_napi_off;
>>>  	ravb_emac_init(ndev);
>>>  
>>> +	error = ravb_set_gti(ndev);
>>> +	if (error)
>>> +		goto out_dma_stop;
>>> +
>>
>>    Hm... belongs in ravb_dmac_init() now, as it seems... 
> 
> Isn't it PTP specific?

   I just had an impression it belonged to the AVB-DMAC register range
but perhaps I'm wrong...

[...]

MBR, Sergey