linux-kernel - Re: [PATCH v7 1/4] soc: mediatek: Refine scpsys to support multiple platform

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Date:	Mon, 11 Jul 2016 15:10:59 +0200
From:	Matthias Brugger <matthias.bgg@...il.com>
To:	James Liao <jamesjj.liao@...iatek.com>
Cc:	Sascha Hauer <kernel@...gutronix.de>,
	Rob Herring <robh@...nel.org>,
	Kevin Hilman <khilman@...nel.org>,
	Daniel Kurtz <djkurtz@...omium.org>,
	srv_heupstream@...iatek.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v7 1/4] soc: mediatek: Refine scpsys to support multiple
 platform



On 11/07/16 10:56, James Liao wrote:

[...]

>>>>> @@ -467,28 +386,54 @@ static int scpsys_probe(struct platform_device *pdev)
>>>>>    			if (PTR_ERR(scpd->supply) == -ENODEV)
>>>>>    				scpd->supply = NULL;
>>>>>    			else
>>>>> -				return PTR_ERR(scpd->supply);
>>>>> +				return ERR_CAST(scpd->supply);
>>>>>    		}
>>>>>    	}
>>>>>
>>>>> -	pd_data->num_domains = NUM_DOMAINS;
>>>>> +	pd_data->num_domains = num;
>>>>>
>>>>> -	for (i = 0; i < NUM_DOMAINS; i++) {
>>>>> +	init_clks(pdev, clk);
>>>>> +
>>>>> +	for (i = 0; i < num; i++) {
>>>>>    		struct scp_domain *scpd = &scp->domains[i];
>>>>>    		struct generic_pm_domain *genpd = &scpd->genpd;
>>>>>    		const struct scp_domain_data *data = &scp_domain_data[i];
>>>>>
>>>>> +		for (j = 0; j < MAX_CLKS && data->clk_id[j]; j++) {
>>>>> +			struct clk *c = clk[data->clk_id[j]];
>>>>> +
>>>>> +			if (IS_ERR(c)) {
>>>>> +				dev_err(&pdev->dev, "%s: clk unavailable\n",
>>>>> +					data->name);
>>>>> +				return ERR_CAST(c);
>>>>> +			}
>>>>> +
>>>>> +			scpd->clk[j] = c;
>>>>
>>>> Put this in the else branch. Apart from that is there any reason you
>>>
>>> Do you mean to change like this?
>>>
>>> 	if (IS_ERR(c)) {
>>> 		...
>>> 		return ERR_CAST(c);
>>> 	} else {
>>> 		scpd->clk[j] = c;
>>> 	}
>>>
>>> checkpatch.pl will warn for above code due to it returns in 'if' branch.
>>>
>>
>> I tried that on top of next-20160706 and it checkpatch didn't throw any
>> warning. Which kernel version are based on?
>
> I don't remember which version of checkpatch warn on this pattern. This
> patch series develop across several kernel versions.

We as the kernel community develop against master or linux-next. We only 
care about older kernel version in the sense that we intent hard not to 
break any userspace/kernel or firmware/kernel interfaces. Apart from 
that it's up to every individual to backport patches from mainline 
kernel to his respective version. But that's nothing the community as a 
hole can take care of.

>
> So do you prefer to put "scpd->clk[j] = c;" into 'else' branch?
>

Yes please :)

>>>> moved the for up in the function? If not, I would prefer not to move it,
>>>> to make it easier to read the diff.
>>>
>>> The new 'for' block are far different from original one. And I think
>>> it's easy to read if we keep simple assign statements in the same block.
>>>
>>
>> It's different in the sense that it checks if struct clk *c is an error.
>> I don't see the reason why we need to move it up in the file.
>> It's not too important but I would prefer not to move it if there is no
>> reason.
>
> I think I may misunderstand your comments. Which 'for' block did you
> mention for? 'for (i = 0; i < num ...' or 'for (j = 0; j < MAX_CLKS
> && ...' ?
>
> The 'for(i)' exists in original code, this patch just change its counter
> from 'NUM_DOMAINS' to 'num'. The 'for(j)' is a new for-block, so it was
> not moved from other blocks.
>

for (j = 0; j < MAX_CLKS... is present in the actual scpsys_probe in 
linux-next (line 485 as of today). This patch moves this for a few lines 
up, to be precise before executing this code sequence:
<code>
pd_data->domains[i] = genpd;
scpd->scp = scp;

scpd->data = data;
</code>

AFAIK there is no reason to do so. It adds unnecessary complexity to the 
patch. So please fix this together with the other comments you got.

Thanks a lot,
Matthias