[RFC] i.MX: drop secondary clocks

On Fri, Mar 09, 2012 at 03:44:31PM +0100, Lothar Wa?mann wrote:

Hi,

Sascha Hauer writes:

quoted

On Fri, Mar 09, 2012 at 12:47:58PM +0100, Lothar Wa?mann wrote:

quoted

Hi,

Sascha Hauer writes:

quoted

On Fri, Mar 09, 2012 at 10:32:30AM +0100, Lothar Wa?mann wrote:

quoted

Hi,

Sascha Hauer writes:

quoted

Hi All,

[...]

quoted

quoted

I think that's a bad idea! Drivers should not have to know intimate
details about the clock logic of the CPU core they are running on!

They don't have to. There really are different clocks connected to the
devices. If for example you have a look eSDHC Block diagram in the
reference Manual  you'll see that this has three clock inputs. All
we do is to tell the driver about these three clocks which are device
specific and not SoC specific. Which of these clocks are actually
gatetable varies from SoC to SoC. Also on some SoCs two of the three
clocks may be actually the same.

At least this should be done in a way that is independent from the
name of the clock on a specific SoC, but is related to the function of
the clock for the driver. Thus instead of e.g. CLK_IPG and CLK_PER use
CLK_REG and CLK_BITRATE.

'per', 'ipg' and 'ahb' seems to be a common pattern with all i.MXs. Only
ahb is sometimes refered to as hclk. Do you also have a name for
ahb/hclk? I don't insist on specific names, in the end they are just
names and the pattern I used at least seems mostly consistent.

CLK_BUS?

quoted

I assume that any given device has a set of clocks as inputs which
should get device specific names. It's the job of the clock tree
to know which SoC clocks map to which device clocks. If now a newer
UART block has an additional clock, then we would depending on the
device id (fsl,imx7-uart) know that it requires the additional clock
and request it.

It's also not the business of a device driver to know any details
about clock dependencies on a specific SoC.
We probably really need a bus layer that can hide the details of the
bus architecture and their corresponding clocks from the device
drivers.

I agree there's room for improvements, but I don't want to make that a
dependency for the generic clock support.

Does anyone know which clocks are really worth to be turned off for
powermanement? I have no idea whether we really save power when we for
example turn off aips_tz1_clk.

Sascha

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