clk: at91: rework rm9200 USB clock to propagate set_rate to the parent clk

The RM9200 USB clock is actually connected to a single parent (the PLLB)
on which we can apply a specific divider.
The USB clock divider does not allow for fine grained control on the USB
clock frequency, hence propagating the set_rate request to the parent is
the only choice we have to properly configure the USB clock rate.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Reported-by: Gaël PORTAY <gael.portay@gmail.com>
Tested-by: Gaël PORTAY <gael.portay@gmail.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>

1 files changed, 10 insertions, 3 deletions

diff --git a/drivers/clk/at91/clk-usb.c b/drivers/clk/at91/clk-usb.c
index 7d1d26a4bd04..183877712c6c 100644
--- a/drivers/clk/at91/clk-usb.c
+++ b/drivers/clk/at91/clk-usb.c
@@ -238,16 +238,22 @@ static long at91rm9200_clk_usb_round_rate(struct clk_hw *hw, unsigned long rate,
                                           unsigned long *parent_rate)
 {
         struct at91rm9200_clk_usb *usb = to_at91rm9200_clk_usb(hw);
+        struct clk *parent = __clk_get_parent(hw->clk);
         unsigned long bestrate = 0;
         int bestdiff = -1;
         unsigned long tmprate;
         int tmpdiff;
         int i = 0;
 
-        for (i = 0; i < 4; i++) {
+        for (i = 0; i < RM9200_USB_DIV_TAB_SIZE; i++) {
+                unsigned long tmp_parent_rate;
+
                 if (!usb->divisors[i])
                         continue;
-                tmprate = *parent_rate / usb->divisors[i];
+
+                tmp_parent_rate = rate * usb->divisors[i];
+                tmp_parent_rate = __clk_round_rate(parent, tmp_parent_rate);
+                tmprate = tmp_parent_rate / usb->divisors[i];
                 if (tmprate < rate)
                         tmpdiff = rate - tmprate;
                 else
@@ -256,6 +262,7 @@ static long at91rm9200_clk_usb_round_rate(struct clk_hw *hw, unsigned long rate,
                 if (bestdiff < 0 || bestdiff > tmpdiff) {
                         bestrate = tmprate;
                         bestdiff = tmpdiff;
+                        *parent_rate = tmp_parent_rate;
                 }
 
                 if (!bestdiff)
@@ -311,7 +318,7 @@ at91rm9200_clk_register_usb(struct at91_pmc *pmc, const char *name,
         init.ops = &at91rm9200_usb_ops;
         init.parent_names = &parent_name;
         init.num_parents = 1;
-        init.flags = 0;
+        init.flags = CLK_SET_RATE_PARENT;
 
         usb->hw.init = &init;
         usb->pmc = pmc;