On Tue, Apr 24, 2012 at 07:12:10PM +0530, viresh kumar wrote:

On 4/24/12, Andrew Lunn [off-list ref] wrote:

quoted

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