linux-kernel - Re: [PATCH net 2/2] net: ravb: Check that GTI loading request is done

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Date:   Thu, 14 Dec 2023 15:02:38 +0200
From:   claudiu beznea <claudiu.beznea@...on.dev>
To:     Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>
Cc:     s.shtylyov@....ru, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com,
        claudiu.beznea.uj@...renesas.com, yoshihiro.shimoda.uh@...esas.com,
        wsa+renesas@...g-engineering.com, biju.das.jz@...renesas.com,
        prabhakar.mahadev-lad.rj@...renesas.com,
        mitsuhiro.kimura.kc@...esas.com, geert+renesas@...der.be,
        netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 2/2] net: ravb: Check that GTI loading request is done



On 14.12.2023 14:33, Niklas Söderlund wrote:
> Hi Claudiu,
> 
> Thanks for your work.
> 
> On 2023-12-14 13:31:37 +0200, Claudiu wrote:
>> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>>
>> Hardware manual specifies the following for GCCR.LTI bit:
>> 0: Setting completed
>> 1: When written: Issue a configuration request.
>> When read: Completion of settings is pending
> 
> This is hard to parse at first glance, the last row have odd indentation 
> and the mixing of read and write info is odd. I know this reflects how 
> it's written in the datasheet, but at least there the indentation is 
> correct. Also missing here is the fact that only 1 can be written to the 
> bit.
> 
>>
>> Thus, check the completion status when setting 1 to GCCR.LTI.
> 
> Can you describe in the commit why this fix is needed. I agree it is, 
> but would be nice to record why. As this have a fixes tags have you hit 
> an issue? Or are you correcting the driver based on the datasheet?

Yes, this is a issue I faced while working on runtime PM support for this
driver.

> 
> Maybe a more informative commit message could be to describe the change 
> and why it's needed instead of the register layout?

ok

> 
>   The driver do not wait for the confirmation of the configuring request 
>   of the gPTP timer increment before moving on. Add a check to make sure 
>   the request completes successfully.
> 
>>
>> Fixes: 7e09a052dc4e ("ravb: Exclude gPTP feature support for RZ/G2L")
>> Fixes: 568b3ce7a8ef ("ravb: factor out register bit twiddling code")
>> Fixes: 0184165b2f42 ("ravb: add sleep PM suspend/resume support")
>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
>> ---
>>  drivers/net/ethernet/renesas/ravb_main.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>> index ce95eb5af354..1c253403a297 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -2819,6 +2819,10 @@ static int ravb_probe(struct platform_device *pdev)
>>  
>>  		/* Request GTI loading */
>>  		ravb_modify(ndev, GCCR, GCCR_LTI, GCCR_LTI);
>> +		/* Check completion status. */
>> +		error = ravb_wait(ndev, GCCR, GCCR_LTI, 0);
>> +		if (error)
>> +			goto out_disable_refclk;
> 
> nit: Maybe create a helper for this so future fixes only need to be 
> addressed in one location?

The code intended for runtime PM support addresses this.

> 
>>  	}
>>  
>>  	if (info->internal_delay) {
>> @@ -3041,6 +3045,10 @@ static int __maybe_unused ravb_resume(struct device *dev)
>>  
>>  		/* Request GTI loading */
>>  		ravb_modify(ndev, GCCR, GCCR_LTI, GCCR_LTI);
>> +		/* Check completion status. */
>> +		ret = ravb_wait(ndev, GCCR, GCCR_LTI, 0);
>> +		if (ret)
>> +			return ret;
>>  	}
>>  
>>  	if (info->internal_delay)
>> -- 
>> 2.39.2
>>
>