netdev - Re: [PATCH net-next v2 5/5] net: ravb: Add runtime PM support

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Date: Tue, 13 Feb 2024 08:59:05 +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
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 5/5] net: ravb: Add runtime PM support



On 12.02.2024 22:19, Sergey Shtylyov wrote:
> On 2/12/24 10:56 AM, claudiu beznea 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
>>>
>>>    This pesky "registers' content" somehow evaded me -- should be "register
>>> contents" as well...
>>>
>>>> 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).
>>>>
>>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>>> Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
>>> [...]
>>>
>>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>>> index f4be08f0198d..5bbfdfeef8a9 100644
>>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>>> @@ -1939,16 +1939,21 @@ static int ravb_open(struct net_device *ndev)
>>>>  {
>>>>  	struct ravb_private *priv = netdev_priv(ndev);
>>>>  	const struct ravb_hw_info *info = priv->info;
>>>> +	struct device *dev = &priv->pdev->dev;
>>>>  	int error;
>>>>  
>>>>  	napi_enable(&priv->napi[RAVB_BE]);
>>>>  	if (info->nc_queues)
>>>>  		napi_enable(&priv->napi[RAVB_NC]);
>>>>  
>>>> +	error = pm_runtime_resume_and_get(dev);
>>>> +	if (error < 0)
>>>> +		goto out_napi_off;
>>>
>>>    Well, s/error/ret/ -- it would fit better here...
>>
>> Using error is the "trademark" of this driver, it is used all around the
>> driver. I haven't introduced it here, I don't like it. The variable error
> 
>    Heh, because it's my usual style. Too bad you don't like it... :-)
> 
>> in this particular function is here from the beginning of the driver.
> 
>    I think it's well suited for the functions returning either 0 or a
> (negative) error code. It's *if* (error < 0) that confuses me (as this
> API can return positive numbers in case of success...
> 
>> So, I don't consider changing error to ret is the scope of this series.
> 
>    OK, you're probably right... are you going to respin the series because
> of Biju's comments?

Yes!

Thank you,
Claudiu Beznea

> 
> [...]
>>>> @@ -3066,6 +3089,12 @@ static void ravb_remove(struct platform_device *pdev)
>>>>  	struct net_device *ndev = platform_get_drvdata(pdev);
>>>>  	struct ravb_private *priv = netdev_priv(ndev);
>>>>  	const struct ravb_hw_info *info = priv->info;
>>>> +	struct device *dev = &priv->pdev->dev;
>>>> +	int error;
>>>> +
>>>> +	error = pm_runtime_resume_and_get(dev);
>>>> +	if (error < 0)
>>>> +		return;
>>>
>>>    Again, s/erorr/ret/ in this case.
>>
>> error was used here to comply with the rest of the driver. So, if you still
>> want me to change it here and in ravb_remove() please confirm.
> 
>    No, we are good enough without that; I'll consider doing a cleanup
> when/if I have time. :-)
> 
>> Thank you,
>> Claudiu Beznea
> 
> MBR, Sergey