On Tue, Apr 24, 2012 at 07:12:10PM +0530, viresh kumar wrote:
> On 4/24/12, Andrew Lunn <andrew@xxxxxxx> wrote:
> > Sorry, but still wrong.
> >
> > The clock is optional. If we can find a clock, turn it on. If not,
> > keep going....
> >
> > You patch causes the missing clock to become a fatal error.
> >
> > This sata_mv exists in multiple forms. It can be part of a SoC. It can
> > also be on a PCI bus. In the PCI form, it is unlikely to have a clk
> > which can be controlled. When built into a SoC, namely one of the
> > Orion family, dove, orion5x, mv78xx0 do not have a clock which can be
> > controlled. However kirkwood does have a clock.
> >
> > So, kirkwood will provide a clock and expects that sata_mv will turn
> > it on. All the other ways of using sata_mv will not provide a clock,
> > but still expect the driver to be happy.
>
> Hmm. What this code does now is:
> If HAVE_CLK is selected, then there must be a clock for the device. Otherwise
> it will always pass.
>
-#if defined(CONFIG_HAVE_CLK)
hpriv->clk = clk_get(&pdev->dev, NULL);
- if (IS_ERR(hpriv->clk))
- dev_notice(&pdev->dev, "cannot get clkdev\n");
- else
- clk_enable(hpriv->clk);
-#endif
+ if (IS_ERR(hpriv->clk)) {
+ dev_err(&pdev->dev, "cannot get clkdev\n");
+ return PTR_ERR(hpriv->clk);
+ }
+
+ clk_enable(hpriv->clk);
There are three use cases....
1) The platform does not implement HAVE_CLK. So we are using your NOP
operations.
clk_get() returns NULL.
IS_ERR(NULL) is false. So it keeps going, calls clk_enable() which is
also NOP and the driver is happy.
2) The platform does have HAVE_CLK. So we are using driver/clk/
code. There is no clk defined for the device, since there is no
controllable clk. Its using the PCI clock, or some hard wired
internal SoC clock.
clk_get() returns ERR_PTR(-ENOENT)
IS_ERR(hpriv->clk) is true, you output a dev_err() and the device
probe fails.
This is wrong. Not having the clk is not fatal. The old code would
carefully not call clk_enable(), since it has an error pointer, not
have a valid clk, and would also not call clk_disable during
removal.
3) The platform does have HAVE_CLK. So we are using driver/clk/ code.
There is however a gateable clock driving this lump of silicon.
clk_get() returns a valid pointer to a clk.
IS_ERR(hpriv->clk) is false, so it keeps going.
clk_enable() is called and the driver is happy.
Well, actually, his brings up a new issues
static int __clk_enable(struct clk *clk)
{
int ret = 0;
if (!clk)
return 0;
if (WARN_ON(clk->prepare_count == 0))
return -ESHUTDOWN;
this should actually be clk_prepare_enable(). Did you see my
patches adding generic clk framework support for Orion. I fixed
this as part of that patch set.
Anyway.... You asked:
> You want not to return error if a platform does have HAVE_CLK, but
> doesn't have a clock for sata? That would be simple to fix, but want
> to confirm if this is actually required.
Correct.
Andrew
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