clk: at91: sam9x7: add support for HW PLL freq dividers

Add support for hardware dividers for PLL IDs in sam9x7 SoC. The system
PLL - PLLA and the system PLL divided by 2 - PLLADIV2 with PLL ID 0 and
4 respectively, both have a hardware divider /2. This has to be taken into
account in the software to obtain the right frequencies. Support for the
same is added in the PLL driver.

fcorepllack -----> HW Div = 2 -+--> fpllack
                               |
                               +--> HW Div = 2 ---> fplladiv2ck

In this case the corepll freq is 1600 MHz. So, the plla freq is 800 MHz
after the hardware divider and the plladiv2 freq is 400 MHz after the
hardware divider (given that the DIVPMC is 0).

Signed-off-by: Varshini Rajendran <[email protected]>
Reviewed-by: Claudiu Beznea <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Claudiu Beznea <[email protected]>

Author: varshini-rajendran

drivers/clk/at91/clk-sam9x60-pll.c

@@ -73,9 +73,15 @@ static unsigned long sam9x60_frac_pll_recalc_rate(struct clk_hw *hw,
 {
 	struct sam9x60_pll_core *core = to_sam9x60_pll_core(hw);
 	struct sam9x60_frac *frac = to_sam9x60_frac(core);
+	unsigned long freq;
 
-	return parent_rate * (frac->mul + 1) +
+	freq = parent_rate * (frac->mul + 1) +
 		DIV_ROUND_CLOSEST_ULL((u64)parent_rate * frac->frac, (1 << 22));
+
+	if (core->layout->div2)
+		freq >>= 1;
+
+	return freq;
 }
 
 static int sam9x60_frac_pll_set(struct sam9x60_pll_core *core)
@@ -432,6 +438,12 @@ static unsigned long sam9x60_div_pll_recalc_rate(struct clk_hw *hw,
 	return DIV_ROUND_CLOSEST_ULL(parent_rate, (div->div + 1));
 }
 
+static unsigned long sam9x60_fixed_div_pll_recalc_rate(struct clk_hw *hw,
+						       unsigned long parent_rate)
+{
+	return parent_rate >> 1;
+}
+
 static long sam9x60_div_pll_compute_div(struct sam9x60_pll_core *core,
 					unsigned long *parent_rate,
 					unsigned long rate)
@@ -606,6 +618,16 @@ static const struct clk_ops sam9x60_div_pll_ops_chg = {
 	.restore_context = sam9x60_div_pll_restore_context,
 };
 
+static const struct clk_ops sam9x60_fixed_div_pll_ops = {
+	.prepare = sam9x60_div_pll_prepare,
+	.unprepare = sam9x60_div_pll_unprepare,
+	.is_prepared = sam9x60_div_pll_is_prepared,
+	.recalc_rate = sam9x60_fixed_div_pll_recalc_rate,
+	.round_rate = sam9x60_div_pll_round_rate,
+	.save_context = sam9x60_div_pll_save_context,
+	.restore_context = sam9x60_div_pll_restore_context,
+};
+
 struct clk_hw * __init
 sam9x60_clk_register_frac_pll(struct regmap *regmap, spinlock_t *lock,
 			      const char *name, const char *parent_name,
@@ -725,10 +747,14 @@ sam9x60_clk_register_div_pll(struct regmap *regmap, spinlock_t *lock,
 	else
 		init.parent_names = &parent_name;
 	init.num_parents = 1;
-	if (flags & CLK_SET_RATE_GATE)
+
+	if (layout->div2)
+		init.ops = &sam9x60_fixed_div_pll_ops;
+	else if (flags & CLK_SET_RATE_GATE)
 		init.ops = &sam9x60_div_pll_ops;
 	else
 		init.ops = &sam9x60_div_pll_ops_chg;
+
 	init.flags = flags;
 
 	div->core.id = id;

drivers/clk/at91/pmc.h

@@ -64,6 +64,7 @@ struct clk_pll_layout {
 	u8 frac_shift;
 	u8 div_shift;
 	u8 endiv_shift;
+	u8 div2;
 };
 
 extern const struct clk_pll_layout at91rm9200_pll_layout;