linux-kernel - [V2] [PATCH] clk: zynqmp: pll: add set_pll_mode to check condition in zynqmp_pll

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Date:   Tue, 30 Mar 2021 20:17:01 +0800
From:   quanyang.wang@...driver.com
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rajan Vaja <rajan.vaja@...inx.com>,
        Jolly Shah <jolly.shah@...inx.com>,
        Quanyang Wang <quanyang.wang@...driver.com>,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [V2] [PATCH] clk: zynqmp: pll: add set_pll_mode to check condition in zynqmp_pll_enable

From: Quanyang Wang <quanyang.wang@...driver.com>

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.

Signed-off-by: Quanyang Wang <quanyang.wang@...driver.com>
Tested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
---
V2:
 - add Tested-by tag, thanks Laurent.
 - fix typos in commit message and multiline code comments
---
 drivers/clk/zynqmp/pll.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/zynqmp/pll.c b/drivers/clk/zynqmp/pll.c
index 92f449ed38e5..fa89ee722a6d 100644
--- a/drivers/clk/zynqmp/pll.c
+++ b/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",
-- 
2.25.1