From: santosh.shilimkar@ti•com (Santosh Shilimkar)
To: linux-arm-kernel@lists•infradead.org
Subject: Regression (ARM) arch/arm/mm/init.c doesn't build without CONFIG_ARM_PATCH_PHYS_VIRT.
Date: Mon, 6 Jan 2014 18:42:13 -0500 [thread overview]
Message-ID: <52CB3F55.1050404@ti.com> (raw)
In-Reply-To: <20140106223906.GH27432@n2100.arm.linux.org.uk>
On Monday 06 January 2014 05:39 PM, Russell King - ARM Linux wrote:
> On Mon, Jan 06, 2014 at 08:28:20PM +0100, Krzysztof Ha?asa wrote:
>> Russell, Santosh,
>>
>> the unneeded commit causing regression is still in place. Please try to
>> compile an ARM kernel without CONFIG_ARM_PATCH_PHYS_VIRT and with
>> CONFIG_ZONE_DMA and see for yourself, if you don't believe me.
>>
>> Please be aware that this commit fixes nothing, its only function is
>> causing the regression - so we don't lose anything by reverting it.
>>
>> If the attached wasn't clear, what the defective commit presently does
>> is changing a perfectly valid code into a code referencing a variable
>> which (without CONFIG_ARM_PATCH_PHYS_VIRT set) doesn't at all exist.
>>
>> With CONFIG_ARM_PATCH_PHYS_VIRT set, this commit does precisely nothing.
>
> Right, so, with Assabet, which has CONFIG_DMA_ZONE=y and
> CONFIG_ARM_PATCH_PHYS_VIRT=y:
>
> $ make O=../build/assabet arch/arm/mm/init.i
>
> gives:
> arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1;
>
> with or without Santosh's patch. So, with V2P patching in place, there's
> absolutely no functional difference.
>
> With CONFIG_ARM_PATCH_PHYS_VIRT=n, before Santosh's patch:
>
> arm_dma_limit = (0xc0000000UL) + arm_dma_zone_size - 1;
>
> After:
>
> arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1;
>
> and this breaks the build because there is no __pv_phys_offset symbol.
>
> Now, the case which matters for Santosh is the first case - the one
> where CONFIG_ARM_PATCH_PHYS_VIRT=y. We can clearly see that after
> preprocessing, the results are 100% identical.
>
> Therefore, I find myself agreeing with Krzysztof that the commit is
> bad, has no functional change for the case it was proposed to solve,
> and needs to be reverted.
>
May be I missed your point but I ended up creating the patch because
the CMA reservation was failing on Keystone since the arm_dma_limit
wasn't right since it wasn't considering the actual __pv_phys_offset.
Isn't that an issue ?
Regards,
Santosh
next prev parent reply other threads:[~2014-01-06 23:42 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-31 11:20 Regression (ARM) arch/arm/mm/init.c doesn't build without CONFIG_ARM_PATCH_PHYS_VIRT Krzysztof Hałasa
2013-12-31 11:23 ` Russell King - ARM Linux
2014-01-01 14:40 ` Krzysztof Hałasa
2014-01-06 19:28 ` Krzysztof Hałasa
2014-01-06 19:33 ` Santosh Shilimkar
2014-01-06 22:08 ` Krzysztof Hałasa
2014-01-06 22:27 ` Santosh Shilimkar
2014-01-06 22:39 ` Russell King - ARM Linux
2014-01-06 23:42 ` Santosh Shilimkar [this message]
2014-01-07 1:11 ` Russell King - ARM Linux
2014-01-07 17:45 ` Santosh Shilimkar
2014-01-07 17:55 ` Russell King - ARM Linux
2014-01-08 6:40 ` Krzysztof Hałasa
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