[PATCH] clk: at91: clk-sam9x60-pll: force write to PLL_UPDT register

[nicolas.ferre at microchip.com]

From: Nicolas Ferre <nicolas.ferre at microchip.com>

This register is important for sequencing the commands to PLLs, so
actually write the update bits with regmap_write_bits() instead of
relying on a read/modify/write regmap command that could skip the actual
hardware write if the value is identical to the one read.

It's changed when modification is needed to the PLL, when
read-only operation is done, we could keep the call to
regmap_update_bits().

Add a comment to the sam9x60_div_pll_set_div() function that uses this
PLL_UPDT register so that it's used consistently, according to the
product's datasheet.

Signed-off-by: Nicolas Ferre <nicolas.ferre at microchip.com>
Tested-by: Ryan Wanner <ryan.wanner at microchip.com> # on sama7d65 and sam9x75
---
 drivers/clk/at91/clk-sam9x60-pll.c | 33 ++++++++++++++++--------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/clk/at91/clk-sam9x60-pll.c b/drivers/clk/at91/clk-sam9x60-pll.c
index cefd9948e103..a3198323126f 100644
--- a/drivers/clk/at91/clk-sam9x60-pll.c
+++ b/drivers/clk/at91/clk-sam9x60-pll.c
@@ -93,7 +93,7 @@ static int sam9x60_frac_pll_set(struct sam9x60_pll_core *core)
 
 	spin_lock_irqsave(core->lock, flags);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_ID_MSK, core->id);
 	regmap_read(regmap, AT91_PMC_PLL_CTRL1, &val);
 	cmul = (val & core->layout->mul_mask) >> core->layout->mul_shift;
@@ -128,7 +128,7 @@ static int sam9x60_frac_pll_set(struct sam9x60_pll_core *core)
 		udelay(10);
 	}
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK,
 			   AT91_PMC_PLL_UPDT_UPDATE | core->id);
 
@@ -136,7 +136,7 @@ static int sam9x60_frac_pll_set(struct sam9x60_pll_core *core)
 			   AT91_PMC_PLL_CTRL0_ENLOCK | AT91_PMC_PLL_CTRL0_ENPLL,
 			   AT91_PMC_PLL_CTRL0_ENLOCK | AT91_PMC_PLL_CTRL0_ENPLL);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK,
 			   AT91_PMC_PLL_UPDT_UPDATE | core->id);
 
@@ -164,7 +164,7 @@ static void sam9x60_frac_pll_unprepare(struct clk_hw *hw)
 
 	spin_lock_irqsave(core->lock, flags);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_ID_MSK, core->id);
 
 	regmap_update_bits(regmap, AT91_PMC_PLL_CTRL0, AT91_PMC_PLL_CTRL0_ENPLL, 0);
@@ -173,7 +173,7 @@ static void sam9x60_frac_pll_unprepare(struct clk_hw *hw)
 		regmap_update_bits(regmap, AT91_PMC_PLL_ACR,
 				   AT91_PMC_PLL_ACR_UTMIBG | AT91_PMC_PLL_ACR_UTMIVR, 0);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK,
 			   AT91_PMC_PLL_UPDT_UPDATE | core->id);
 
@@ -262,7 +262,7 @@ static int sam9x60_frac_pll_set_rate_chg(struct clk_hw *hw, unsigned long rate,
 
 	spin_lock_irqsave(core->lock, irqflags);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK,
 			   core->id);
 	regmap_read(regmap, AT91_PMC_PLL_CTRL1, &val);
 	cmul = (val & core->layout->mul_mask) >> core->layout->mul_shift;
@@ -275,7 +275,7 @@ static int sam9x60_frac_pll_set_rate_chg(struct clk_hw *hw, unsigned long rate,
 		     (frac->mul << core->layout->mul_shift) |
 		     (frac->frac << core->layout->frac_shift));
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK,
 			   AT91_PMC_PLL_UPDT_UPDATE | core->id);
 
@@ -284,7 +284,7 @@ static int sam9x60_frac_pll_set_rate_chg(struct clk_hw *hw, unsigned long rate,
 			   AT91_PMC_PLL_CTRL0_ENLOCK |
 			   AT91_PMC_PLL_CTRL0_ENPLL);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK,
 			   AT91_PMC_PLL_UPDT_UPDATE | core->id);
 
@@ -338,7 +338,10 @@ static const struct clk_ops sam9x60_frac_pll_ops_chg = {
 	.restore_context = sam9x60_frac_pll_restore_context,
 };
 
-/* This function should be called with spinlock acquired. */
+/* This function should be called with spinlock acquired.
+ * Warning: this function must be called only if the same PLL ID was set in
+ *          PLL_UPDT register previously.
+ */
 static void sam9x60_div_pll_set_div(struct sam9x60_pll_core *core, u32 div,
 				    bool enable)
 {
@@ -350,7 +353,7 @@ static void sam9x60_div_pll_set_div(struct sam9x60_pll_core *core, u32 div,
 			   core->layout->div_mask | ena_msk,
 			   (div << core->layout->div_shift) | ena_val);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK,
 			   AT91_PMC_PLL_UPDT_UPDATE | core->id);
 
@@ -366,7 +369,7 @@ static int sam9x60_div_pll_set(struct sam9x60_pll_core *core)
 	unsigned int val, cdiv;
 
 	spin_lock_irqsave(core->lock, flags);
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_ID_MSK, core->id);
 	regmap_read(regmap, AT91_PMC_PLL_CTRL0, &val);
 	cdiv = (val & core->layout->div_mask) >> core->layout->div_shift;
@@ -398,13 +401,13 @@ static void sam9x60_div_pll_unprepare(struct clk_hw *hw)
 
 	spin_lock_irqsave(core->lock, flags);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_ID_MSK, core->id);
 
 	regmap_update_bits(regmap, AT91_PMC_PLL_CTRL0,
 			   core->layout->endiv_mask, 0);
 
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT,
 			   AT91_PMC_PLL_UPDT_UPDATE | AT91_PMC_PLL_UPDT_ID_MSK,
 			   AT91_PMC_PLL_UPDT_UPDATE | core->id);
 
@@ -518,7 +521,7 @@ static int sam9x60_div_pll_set_rate_chg(struct clk_hw *hw, unsigned long rate,
 	div->div = DIV_ROUND_CLOSEST(parent_rate, rate) - 1;
 
 	spin_lock_irqsave(core->lock, irqflags);
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK,
 			   core->id);
 	regmap_read(regmap, AT91_PMC_PLL_CTRL0, &val);
 	cdiv = (val & core->layout->div_mask) >> core->layout->div_shift;
@@ -574,7 +577,7 @@ static int sam9x60_div_pll_notifier_fn(struct notifier_block *notifier,
 	div->div = div->safe_div;
 
 	spin_lock_irqsave(core.lock, irqflags);
-	regmap_update_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK,
+	regmap_write_bits(regmap, AT91_PMC_PLL_UPDT, AT91_PMC_PLL_UPDT_ID_MSK,
 			   core.id);
 	regmap_read(regmap, AT91_PMC_PLL_CTRL0, &val);
 	cdiv = (val & core.layout->div_mask) >> core.layout->div_shift;
-- 
2.43.0