linux-kernel - Re: [PATCH 2/2] misc: sram: switch to ioremap

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Date:	Thu, 8 Jan 2015 21:00:57 +0530
From:	Abhilash Kesavan <kesavan.abhilash@...il.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Philipp Zabel <p.zabel@...gutronix.de>,
	Tony Lindgren <tony@...mide.com>,
	linux-rockchip@...ts.infradead.org,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Santosh Shilimkar <santosh.shilimkar@...com>,
	"heiko@...ech.de" <heiko@...ech.de>,
	"Li.Xiubo@...escale.com" <Li.Xiubo@...escale.com>,
	"shc_work@...l.ru" <shc_work@...l.ru>,
	"nicoleotsuka@...il.com" <nicoleotsuka@...il.com>,
	"arnd@...db.de" <arnd@...db.de>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"corbet@....net" <corbet@....net>,
	"padma.v@...sung.com" <padma.v@...sung.com>,
	"alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
	"shawn.guo@...escale.com" <shawn.guo@...escale.com>,
	"bcousson@...libre.com" <bcousson@...libre.com>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"kgene@...nel.org" <kgene@...nel.org>,
	Pawel Moll <Pawel.Moll@....com>
Subject: Re: [PATCH 2/2] misc: sram: switch to ioremap_wc from ioremap

Hi Rob and Philipp,

On Tue, Jan 6, 2015 at 10:57 PM, Rob Herring <robherring2@...il.com> wrote:
> On Tue, Jan 6, 2015 at 10:54 AM, Philipp Zabel <p.zabel@...gutronix.de> wrote:
>> Hi Abhilash,
>>
>> Am Dienstag, den 06.01.2015, 19:57 +0530 schrieb Abhilash Kesavan:
>>> >> From the existing dts files, omap, imx, rockchip and exynos seem to be
>>> >> the only users of the sram allocator code. I have tested this on
>>> >> Exynos5420, Exynos5800 and Exynos7; there is no change in behavior
>>> >> seen on these boards. Tested-by for other SoCs would be appreciated.
>>> >
>>> > Sorry for the delay, these seems to boot OK on omap4, so from that
>>> > point of view:
>>> >
>>> > Tested-by: Tony Lindgren <tony@...mide.com>
>>>
>>> Thanks a lot for testing this. If someone with imx and rockchip boards
>>> could help test this out, then we could look to get this in.
>>
>> This shouldn't be a problem on i.MX, the coda driver doesn't access SRAM
>> from the CPU at all.
>
> Audio buffers are typically (perhaps not in mainline) in SRAM on i.MX
> chips which are accessed by CPU and probably mmap'ed to userspace.
> That could cause a mismatch in mappings although I would not expect
> both the kernel and user space to touch the buffer. That being said, I
> don't think this change should cause problems for i.MX (from what I
> can remember).

Thanks for the confirmation regarding the i.MX chips. That leaves
rockchip, can someone help with it please ?

Regards,
Abhilash
>
> Rob
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