linux-kernel - Re: [PATCH net-next v3 07/19] net: ravb: Move reference clock enable/disable on runtime PM APIs

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Date: Mon, 8 Jan 2024 10:03:33 +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 07/19] net: ravb: Move reference clock
 enable/disable on runtime PM APIs



On 05.01.2024 21:52, Sergey Shtylyov wrote:
> On 1/5/24 11:23 AM, Claudiu wrote:
> 
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> Reference clock could be or not part of the power domain. If it is part of
>> the power domain, the power domain takes care of propertly setting it. In
>> case it is not part of the power domain and full runtime PM support is
>> available in driver the clock will not be propertly disabled/enabled at
>> runtime. For this, keep the prepare/unprepare operations in the driver's
>> probe()/remove() functions and move the enable/disable in runtime PM
>> functions.
>>
>> Along with it, the other clock request operations were moved close to
>> reference clock request and prepare to have all the clock requests
>> specific code grouped together.
>>
>> Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
> 
>    It's not that I reviewed the squashed version of this patch...

I had a Rb on "net: ravb: Move reference clock enable/disable on runtime PM
APIs" from v2 and an OK from you (no other comments) to do the squash on
"net: ravb: Keep clock request operations grouped together" from v2 thus I
consider keeping Rb is OK.

> 
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>> ---
>>
>> Changes in v3:
>> - squashed with patch 17/21 ("net: ravb: Keep clock request operations grouped
>>   together") from v2
>> - collected tags
>>
>> Changes in v2:
>> - this patch is new and follows the recommendations proposed in the
>>   discussion of patch 08/13 ("net: ravb: Rely on PM domain to enable refclk")
>>   from v2
>>
>>  drivers/net/ethernet/renesas/ravb_main.c | 110 ++++++++++++-----------
>>  1 file changed, 57 insertions(+), 53 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index 844ac3306e93..4673cc2faec0 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> [...]
>> @@ -2697,10 +2692,37 @@ static int ravb_probe(struct platform_device *pdev)
>>  		priv->num_rx_ring[RAVB_NC] = NC_RX_RING_SIZE;
>>  	}
>>  
>> +	priv->clk = devm_clk_get(&pdev->dev, NULL);
>> +	if (IS_ERR(priv->clk)) {
>> +		error = PTR_ERR(priv->clk);
>> +		goto out_reset_assert;
>> +	}
>> +
>> +	if (info->gptp_ref_clk) {
>> +		priv->gptp_clk = devm_clk_get(&pdev->dev, "gptp");
>> +		if (IS_ERR(priv->gptp_clk)) {
>> +			error = PTR_ERR(priv->gptp_clk);
>> +			goto out_reset_assert;
>> +		}
>> +	}
>> +
>> +	priv->refclk = devm_clk_get_optional(&pdev->dev, "refclk");
>> +	if (IS_ERR(priv->refclk)) {
>> +		error = PTR_ERR(priv->refclk);
>> +		goto out_reset_assert;
>> +	}
>> +	clk_prepare(priv->refclk);
>> +
>> +	platform_set_drvdata(pdev, ndev);
> 
>    Why exactly you had to move this line?

Calling pm_runtime_resume_and_get() above will implicitly call the
ravb_runtime_resume() which calls dev_get_drvdata() to get proper data for
refclk.

> 
>> +	pm_runtime_enable(&pdev->dev);
>> +	error = pm_runtime_resume_and_get(&pdev->dev);
>> +	if (error < 0)
>> +		goto out_rpm_disable;
>> +
>>  	priv->addr = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
>>  	if (IS_ERR(priv->addr)) {
>>  		error = PTR_ERR(priv->addr);
>> -		goto out_release;
>> +		goto out_rpm_put;
>>  	}
>>  
>>  	/* The Ether-specific entries in the device structure. */
> [...]
>> @@ -2871,8 +2872,6 @@ static int ravb_probe(struct platform_device *pdev)
>>  	netdev_info(ndev, "Base address at %#x, %pM, IRQ %d.\n",
>>  		    (u32)ndev->base_addr, ndev->dev_addr, ndev->irq);
>>  
>> -	platform_set_drvdata(pdev, ndev);
> 
>    Hm, wasn't calling it here racy?

Haven't noticed that. Racing with who? AFAICT the only functions that uses
this are remove, suspend, resume specific ones.

> 
>> -
>>  	return 0;
>>  
>>  out_napi_del:
> [...]
>> @@ -3060,21 +3058,27 @@ static int ravb_resume(struct device *dev)
>>  	return ret;
>>  }
>>  
>> -static int ravb_runtime_nop(struct device *dev)
>> +static int ravb_runtime_suspend(struct device *dev)
>>  {
>> -	/* Runtime PM callback shared between ->runtime_suspend()
>> -	 * and ->runtime_resume(). Simply returns success.
>> -	 *
>> -	 * This driver re-initializes all registers after
>> -	 * pm_runtime_get_sync() anyway so there is no need
>> -	 * to save and restore registers here.
>> -	 */
> 
>    Perhaps even worth a separate patch to completely remove this function
> which doesn't seem to make sense?

Why? With that the refclk will not be properly enabled/disabled when it
will not be part of the power domain. Take
https://elixir.bootlin.com/linux/v6.7/source/arch/arm64/boot/dts/renesas/beacon-renesom-som.dtsi#L57
as an example. Here refclk is from an external source (not part of power
domain).

Thank you,
Claudiu Beznea

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