clk: zynqmp: pll: add set_pll_mode to check condition in zynqmp_pll_enable

If there is a IOCTL_SET_PLL_FRAC_MODE request sent to ATF ever,
we shouldn't skip invoking PM_CLOCK_ENABLE fn even though this
pll has been enabled. In ATF implementation, it will only assign
the mode to the variable (struct pm_pll *)pll->mode when handling
IOCTL_SET_PLL_FRAC_MODE call. Invoking PM_CLOCK_ENABLE can force
ATF send request to PWU to set the pll mode to PLL's register.

There is a scenario that happens in enabling VPLL_INT(clk_id:96):
1) VPLL_INT has been enabled during booting.
2) A driver calls clk_set_rate and according to the rate, the VPLL_INT
   should be set to FRAC mode. Then zynqmp_pll_set_mode is called
   to pass IOCTL_SET_PLL_FRAC_MODE to ATF. Note that at this point
   ATF just stores the mode to a variable.
3) This driver calls clk_prepare_enable and zynqmp_pll_enable is
   called to try to enable VPLL_INT pll. Because of 1), the function
   zynqmp_pll_enable just returns without doing anything after checking
   that this pll has been enabled.

In the scenario above, the pll mode of VPLL_INT will never be set
successfully. So adding set_pll_mode to check condition to fix it.

Fixes: 3fde0e16 ("drivers: clk: Add ZynqMP clock driver")
Signed-off-by: Quanyang Wang <quanyang.wang@windriver.com>
Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://lore.kernel.org/r/20210406153131.601701-1-quanyang.wang@windriver.comSigned-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/zynqmp/pll.c

@@ -14,10 +14,12 @@
  * struct zynqmp_pll - PLL clock
  * @hw:		Handle between common and hardware-specific interfaces
  * @clk_id:	PLL clock ID
+ * @set_pll_mode:	Whether an IOCTL_SET_PLL_FRAC_MODE request be sent to ATF
  */
 struct zynqmp_pll {
 	struct clk_hw hw;
 	u32 clk_id;
+	bool set_pll_mode;
 };
 
 #define to_zynqmp_pll(_hw)	container_of(_hw, struct zynqmp_pll, hw)
@@ -81,6 +83,8 @@ static inline void zynqmp_pll_set_mode(struct clk_hw *hw, bool on)
 	if (ret)
 		pr_warn_once("%s() PLL set frac mode failed for %s, ret = %d\n",
 			     __func__, clk_name, ret);
+	else
+		clk->set_pll_mode = true;
 }
 
 /**
@@ -240,9 +244,15 @@ static int zynqmp_pll_enable(struct clk_hw *hw)
 	u32 clk_id = clk->clk_id;
 	int ret;
 
-	if (zynqmp_pll_is_enabled(hw))
+	/*
+	 * Don't skip enabling clock if there is an IOCTL_SET_PLL_FRAC_MODE request
+	 * that has been sent to ATF.
+	 */
+	if (zynqmp_pll_is_enabled(hw) && (!clk->set_pll_mode))
 		return 0;
 
+	clk->set_pll_mode = false;
+
 	ret = zynqmp_pm_clock_enable(clk_id);
 	if (ret)
 		pr_warn_once("%s() clock enable failed for %s, ret = %d\n",