Re: [PATCH v11 10/27] iommu/exynos: use managed device helper functions

From: Tomasz Figa
Date: Wed Mar 19 2014 - 08:09:00 EST


On 19.03.2014 10:01, Sachin Kamat wrote:
On 19 March 2014 14:29, Cho KyongHo <pullip.cho@xxxxxxxxxxx> wrote:
On Tue, 18 Mar 2014 16:14:53 +0100, Tomasz Figa wrote:
On 18.03.2014 12:09, Cho KyongHo wrote:
On Fri, 14 Mar 2014 20:52:43 +0530, Sachin Kamat wrote:
Hi KyongHo,

On 14 March 2014 10:35, Cho KyongHo <pullip.cho@xxxxxxxxxxx> wrote:
This patch uses managed device helper functions in the probe().

Signed-off-by: Cho KyongHo <pullip.cho@xxxxxxxxxxx>
---
[snip]

+ data->clk = devm_clk_get(dev, "sysmmu");
+ if (IS_ERR(data->clk)) {
+ dev_info(dev, "No gate clock found!\n");
+ data->clk = NULL;
+ }

Why aren't you returning from here upon error?

It is for the case of a System MMU which does not need clock gating.


Are there really such cases?


Yes.
Especially in the case of initial stage of new SoC development.

I have experianced some software workaround for H/W restriction
needs prevention of clock gating for some devices.

So aren't these basically some exceptions/hacks rather than the usual way
of functioning of the device?


This actually raises a good question, whether we really need to support such early development SoC versions in mainline.

Another thing is that if you need to assure that a clock is ungated, you must acquire it and prepare_enable explicitly, so I don't think this kind of handling is correct.

Best regards,
Tomasz
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