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

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Date:	Tue, 26 May 2015 10:54:22 +0200
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
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 Vladimir,

Am Sonntag, den 24.05.2015, 23:12 +0300 schrieb Vladimir Zapolskiy:
> 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.

res->start is of type phys_addr_t (well, resource_size_t) already.
block->start/size and cur_start/size are just offsets added to it.
I wonder if it wouldn't be more appropriate to use resource_size_t for
the sram_reserve .start field.

> > 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.

See above, start addresses above 4 GiB should be supported even without
extending the offsets to 64-bit.

> If phys_addr_t arguments are accepted, then back to "%pa" vs "0x%llx"
> question:
> 
[...]
> I see that the change preserves the functionality, so I'll change printk
> format to "%pa", will resend the series tomorrow.

Thanks.

regards
Philipp

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