netdev - Re: [PATCH net-next v3 19/19] net: ravb: Add runtime PM support

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Date: Wed, 10 Jan 2024 15:23:24 +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 19/19] net: ravb: Add runtime PM support



On 09.01.2024 21:53, Sergey Shtylyov wrote:
> On 1/5/24 11:23 AM, Claudiu wrote:
> 
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> Add runtime PM support for the ravb driver. As the driver is used by
>> different IP variants, with different behaviors, to be able to have the
>> runtime PM support available for all devices, the preparatory commits
>> moved all the resources parsing and allocations in the driver's probe
>> function and kept the settings for ravb_open(). This is due to the fact
>> that on some IP variants-platforms tuples disabling/enabling the clocks
>> will switch the IP to the reset operation mode where registers' content is
>> lost and reconfiguration needs to be done. For this the rabv_open()
>> function enables the clocks, switches the IP to configuration mode, applies
>> all the registers settings and switches the IP to the operational mode. At
>> the end of ravb_open() IP is ready to send/receive data.
>>
>> In ravb_close() necessary reverts are done (compared with ravb_open()), the
>> IP is switched to reset mode and clocks are disabled.
>>
>> The ethtool APIs or IOCTLs that might execute while the interface is down
>> are either cached (and applied in ravb_open()) or rejected (as at that time
>> the IP is in reset mode). Keeping the IP in the reset mode also increases
>> the power saved (according to the hardware manual).
>>
>> Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> [...]
> 
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index e909960fbc30..e99351fe8d7f 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> [...]
>> @@ -2233,7 +2243,14 @@ static int ravb_close(struct net_device *ndev)
>>  	ravb_get_stats(ndev);
>>  
>>  	/* Set reset mode. */
>> -	return ravb_set_opmode(ndev, CCC_OPC_RESET);
>> +	error = ravb_set_opmode(ndev, CCC_OPC_RESET);
>> +	if (error)
>> +		return error;
>> +
>> +	pm_runtime_mark_last_busy(dev);
>> +	pm_runtime_put_autosuspend(dev);
> 
>    BTW, doesn't make sense to check/return the result?

Most users of this are not checking return code, I followed this pattern,
too. But, yes, would be better to check it, AFAICT.

> 
>> +
>> +	return 0;
>>  }
>>  
>>  static int ravb_hwtstamp_get(struct net_device *ndev, struct ifreq *req)
> [...]
> 
> MBR, Sergey