[PATCH v4 2/5] clk: rockchip: fix up the frac clk get rate error

[Elaine Zhang]

support fractional divider with one level and two level parent clock
.i.e:

normal fractional divider is:
                |--\
    ---[GPLL]---|   \                                      |--\
    ---[CPLL]---|mux|--[GATE]--[DIV]-----------------------|   \
    ---[NPLL]---|   /                |                     |mux|--[GATE]--[UART0]
                |--/                 |--[GATE]--[FRACDIV]--|   /
                                                           |--/
but rk3399 uart is special:
                |--\
    ---[GPLL]---|   \                                         |--\
    ---[CPLL]---|mux|--|--[GATE]--[DIV]-----------------------|   \
    ---[NPLL]---|   /  |                |                     |mux|--[GATE]--[UART1]
                |--/   |                |--[GATE]--[FRACDIV]--|   /
                       |                                      |--/
                       |
                       |                                      |--\
                       |--[GATE]--[DIV]-----------------------|   \
                       |                |                     |mux|--[GATE]--[UART2]
                       |                |--[GATE]--[FRACDIV]--|   /
                       |                                      |--/
                       |
                       |                                      |--\
                       |--[GATE]--[DIV]-----------------------|   \
                                        |                     |mux|--[GATE]--[UART3]
                                        |--[GATE]--[FRACDIV]--|   /
                                                              |--/

The special fractional divider, there are two levels of clock between FRACDIV and PLL.

Signed-off-by: Elaine Zhang <zhangqing at rock-chips.com>
---
 drivers/clk/rockchip/clk.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/clk/rockchip/clk.c b/drivers/clk/rockchip/clk.c
index fac5a4a3f5c3..8f77c3f9fab7 100644
--- a/drivers/clk/rockchip/clk.c
+++ b/drivers/clk/rockchip/clk.c
@@ -190,16 +190,21 @@ static void rockchip_fractional_approximation(struct clk_hw *hw,
 	if (((rate * 20 > p_rate) && (p_rate % rate != 0)) ||
 	    (fd->max_prate && fd->max_prate < p_rate)) {
 		p_parent = clk_hw_get_parent(clk_hw_get_parent(hw));
-		p_parent_rate = clk_hw_get_rate(p_parent);
-		*parent_rate = p_parent_rate;
-		if (fd->max_prate && p_parent_rate > fd->max_prate) {
-			div = DIV_ROUND_UP(p_parent_rate, fd->max_prate);
-			*parent_rate = p_parent_rate / div;
+		if (!p_parent) {
+			*parent_rate = p_rate;
+		} else {
+			p_parent_rate = clk_hw_get_rate(p_parent);
+			*parent_rate = p_parent_rate;
+			if (fd->max_prate && p_parent_rate > fd->max_prate) {
+				div = DIV_ROUND_UP(p_parent_rate,
+						   fd->max_prate);
+				*parent_rate = p_parent_rate / div;
+			}
 		}
 
 		if (*parent_rate < rate * 20) {
-			pr_err("%s parent_rate(%ld) is low than rate(%ld)*20, fractional div is not allowed\n",
-			       clk_hw_get_name(hw), *parent_rate, rate);
+			pr_warn("%s p_rate(%ld) is low than rate(%ld)*20, use integer or half-div\n",
+				clk_hw_get_name(hw), *parent_rate, rate);
 			*m = 0;
 			*n = 1;
 			return;
-- 
2.17.1