linux-kernel - Re: [PATCH V3 07/12] ata/sata_mv: Remove conditional compilation of clk code

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Date:	Wed, 25 Apr 2012 08:43:45 +0200
From:	Lothar Waßmann <LW@...O-electronics.de>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	viresh kumar <viresh.linux@...il.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	sshtylyov@...sta.com, spear-devel@...t.st.com,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	mturquette@...aro.org, akpm@...ux-foundation.org,
	jgarzik@...hat.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V3 07/12] ata/sata_mv: Remove conditional compilation of
 clk code

Hi,

Andrew Lunn writes:
> > This is what i was thinking too and thats why floated this version of patch.
> > But as Andrew said, clk API support is enabled for them, but still they
> > don't have a clk for sata. To get this working, there are two solutions:
> > - Create dummy clk for sata for that platform, so clk_get doesn't fail.
> > - Check for error before every call to clk APIs after clk_get().
> > 
> > Andrew favored the second one. Which means, even on platforms
> > with clk API defined and clk enable required, if there are some issues
> > with lookup table, and clk_get() fails, system may hang when registers
> > are accessed. For this i favored first one.
> 
> I'm not too sure how you are going to achieve 1)
> 
> config SATA_MV
>         tristate "Marvell SATA support"
>         help
>           This option enables support for the Marvell Serial ATA family.
>           Currently supports 88SX[56]0[48][01] PCI(-X) chips,
>           as well as the newer [67]042 PCI-X/PCIe and SOC devices.
> 
> So this driver can be used with anything which has a PCI(-X) or PCIe
> bus, or Orion SoC and a few PowerPC SoCs.
> 
> The SoCs are not too bad, we know which ones they are and we can add
> dummy entries to their device tree. However, how do you want to handle
> the PCI devices? Create the dummy entry somewhere in the middle of the
> PCI core?
> 
> Thought not.
> 
AFAICT the PCI archs do not have HAVE_CLK enabled. Thus they will have
a dummy clk API in place that provides the driver with a non-error
clk_get() return value.


Lothar Waßmann
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