linux-kernel - Re: [PATCH v3 1/9] misc: sram: fix enabled clock leak on error path

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Message-ID: <556230A9.8030307@mentor.com>
Date:	Sun, 24 May 2015 23:12:25 +0300
From:	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
To:	Philipp Zabel <p.zabel@...gutronix.de>
CC:	Heiko Stübner <heiko@...ech.de>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/9] misc: sram: fix enabled clock leak on error path

Hi Philipp,

On 20.05.2015 14:30, Philipp Zabel wrote:
> Hi Vladimir,
> 
> Am Dienstag, den 19.05.2015, 16:11 +0300 schrieb Vladimir Zapolskiy:
>> Hi Philipp,
>>
>> On 19.05.2015 13:41, Philipp Zabel wrote:
>>> Am Montag, den 18.05.2015, 22:08 +0300 schrieb Vladimir Zapolskiy:
>>>> If devm_gen_pool_create() fails, the previously enabled sram->clk is
>>>> not disabled on probe() exit.
>>>>
>>>> Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
>>>> ---
>>>>  drivers/misc/sram.c | 9 +++++----
>>>>  1 file changed, 5 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
>>>> index eeaaf5f..b44a423 100644
>>>> --- a/drivers/misc/sram.c
>>>> +++ b/drivers/misc/sram.c
>>>> @@ -90,16 +90,17 @@ static int sram_probe(struct platform_device *pdev)
>>>>  	if (!sram)
>>>>  		return -ENOMEM;
>>>>  
>>>> +	sram->pool = devm_gen_pool_create(&pdev->dev,
>>>> +					  ilog2(SRAM_GRANULARITY), -1);
>>>> +	if (!sram->pool)
>>>> +		return -ENOMEM;
>>>> +
>>>>  	sram->clk = devm_clk_get(&pdev->dev, NULL);
>>>>  	if (IS_ERR(sram->clk))
>>>>  		sram->clk = NULL;
>>>>  	else
>>>>  		clk_prepare_enable(sram->clk);
>>>
>>> Here you move sram->clk around, and later in patch 7 it gets moved
>>> again. To me it looks like the two should be squashed together.
>>
>> I agree with you, instead of moving sram->pool up it is better to place
>> sram->clk right at the end of probe(), in other words this patch can be
>> safely merged with patch 7 and the series becomes a bit shorter.
>>
>> Thank you for the finding, I'm going to resend the change, please let me
>> know your opinion about "%pa" vs "0x%llx", if it is needed to be changed
>> or not.
> 
> I'd prefer to use %pa for the phys_addr_t types. You could argue that
> %pa is inappropriate as those are addresses relative to the SRAM region,
> not physical addresses as seen by the CPU. But following that argument,
> using phys_addr_t in the first place would not be correct either.

The driver utilizes genalloc gen_pool_add_virt() function, whose
corresponding argument is of phys_addr_t type (and it is correct in my
opinion), the interface to this function dictates the type of its
arguments on client's side.

> Which leads me to question whether we will see larger than 4 GiB SRAM
> regions in the foreseeable future?

The question is not only about SRAM region size, but mainly it is about
the base address of SRAM, and don't want to exclude a situation, when
some kind of SRAM device is found outside of u32 addressable memory
space. Actually I believe an arbitrary physical memory region may be
claimed as it were a "SRAM device" and the driver still works fine.

If phys_addr_t arguments are accepted, then back to "%pa" vs "0x%llx"
question:

From: Philipp Zabel <p.zabel@...gutronix.de>
Date: Tue, 19 May 2015 12:38:37 +0200
In-Reply-To:
<1431976122-4228-4-git-send-email-vladimir_zapolskiy@...tor.com>

> Now that block->start is of type phys_addr_t, is there a reason
> not to use %pa ?

[snip]

>> -		dev_dbg(&pdev->dev, "adding chunk 0x%lx-0x%lx\n",
>> -			cur_start, cur_start + cur_size);
>> +		dev_dbg(&pdev->dev, "adding chunk 0x%llx-0x%llx\n",
>> +			(unsigned long long)cur_start,
>> +			(unsigned long long)cur_start + cur_size);
>
>		dev_dbg(&pdev->dev, "adding chunk 0x%pa-0x%pa\n",
>			&cur_start, &block->start);
>

I see that the change preserves the functionality, so I'll change printk
format to "%pa", will resend the series tomorrow.

--
With best wishes,
Vladimir

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