clk: at91: usb: propagate rate modification to the parent clk

The at91sam9n12 and at91sam9x5 usb clocks do not propagate rate
modification requests to their parents.
This causes a bug when the PLLB is left uninitialized by the bootloader
(PLL multiplier set to 0, or in other words, PLL rate = 0 Hz).

Implement the determinate_rate method and propagate the change rate
request to the parent clk.

Cc: <stable@vger.kernel.org> # v3.14+
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reported-by: Bo Shen <voice.shen@atmel.com>
Tested-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>

1 files changed, 49 insertions, 15 deletions

diff --git a/drivers/clk/at91/clk-usb.c b/drivers/clk/at91/clk-usb.c
index a23ac0c724f0..0b7c3e8840ba 100644
--- a/drivers/clk/at91/clk-usb.c
+++ b/drivers/clk/at91/clk-usb.c
@@ -56,22 +56,55 @@ static unsigned long at91sam9x5_clk_usb_recalc_rate(struct clk_hw *hw,
         return DIV_ROUND_CLOSEST(parent_rate, (usbdiv + 1));
 }
 
-static long at91sam9x5_clk_usb_round_rate(struct clk_hw *hw, unsigned long rate,
-                                          unsigned long *parent_rate)
+static long at91sam9x5_clk_usb_determine_rate(struct clk_hw *hw,
+                                              unsigned long rate,
+                                              unsigned long min_rate,
+                                              unsigned long max_rate,
+                                              unsigned long *best_parent_rate,
+                                              struct clk_hw **best_parent_hw)
 {
-        unsigned long div;
+        struct clk *parent = NULL;
+        long best_rate = -EINVAL;
+        unsigned long tmp_rate;
+        int best_diff = -1;
+        int tmp_diff;
+        int i;
 
-        if (!rate)
-                return -EINVAL;
+        for (i = 0; i < __clk_get_num_parents(hw->clk); i++) {
+                int div;
 
-        if (rate >= *parent_rate)
-                return *parent_rate;
+                parent = clk_get_parent_by_index(hw->clk, i);
+                if (!parent)
+                        continue;
+
+                for (div = 1; div < SAM9X5_USB_MAX_DIV + 2; div++) {
+                        unsigned long tmp_parent_rate;
+
+                        tmp_parent_rate = rate * div;
+                        tmp_parent_rate = __clk_round_rate(parent,
+                                                           tmp_parent_rate);
+                        tmp_rate = DIV_ROUND_CLOSEST(tmp_parent_rate, div);
+                        if (tmp_rate < rate)
+                                tmp_diff = rate - tmp_rate;
+                        else
+                                tmp_diff = tmp_rate - rate;
+
+                        if (best_diff < 0 || best_diff > tmp_diff) {
+                                best_rate = tmp_rate;
+                                best_diff = tmp_diff;
+                                *best_parent_rate = tmp_parent_rate;
+                                *best_parent_hw = __clk_get_hw(parent);
+                        }
+
+                        if (!best_diff || tmp_rate < rate)
+                                break;
+                }
 
-        div = DIV_ROUND_CLOSEST(*parent_rate, rate);
-        if (div > SAM9X5_USB_MAX_DIV + 1)
-                div = SAM9X5_USB_MAX_DIV + 1;
+                if (!best_diff)
+                        break;
+        }
 
-        return DIV_ROUND_CLOSEST(*parent_rate, div);
+        return best_rate;
 }
 
 static int at91sam9x5_clk_usb_set_parent(struct clk_hw *hw, u8 index)
@@ -121,7 +154,7 @@ static int at91sam9x5_clk_usb_set_rate(struct clk_hw *hw, unsigned long rate,
 
 static const struct clk_ops at91sam9x5_usb_ops = {
         .recalc_rate = at91sam9x5_clk_usb_recalc_rate,
-        .round_rate = at91sam9x5_clk_usb_round_rate,
+        .determine_rate = at91sam9x5_clk_usb_determine_rate,
         .get_parent = at91sam9x5_clk_usb_get_parent,
         .set_parent = at91sam9x5_clk_usb_set_parent,
         .set_rate = at91sam9x5_clk_usb_set_rate,
@@ -159,7 +192,7 @@ static const struct clk_ops at91sam9n12_usb_ops = {
         .disable = at91sam9n12_clk_usb_disable,
         .is_enabled = at91sam9n12_clk_usb_is_enabled,
         .recalc_rate = at91sam9x5_clk_usb_recalc_rate,
-        .round_rate = at91sam9x5_clk_usb_round_rate,
+        .determine_rate = at91sam9x5_clk_usb_determine_rate,
         .set_rate = at91sam9x5_clk_usb_set_rate,
 };
 
@@ -179,7 +212,8 @@ at91sam9x5_clk_register_usb(struct at91_pmc *pmc, const char *name,
         init.ops = &at91sam9x5_usb_ops;
         init.parent_names = parent_names;
         init.num_parents = num_parents;
-        init.flags = CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE;
+        init.flags = CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE |
+                     CLK_SET_RATE_PARENT;
 
         usb->hw.init = &init;
         usb->pmc = pmc;
@@ -207,7 +241,7 @@ at91sam9n12_clk_register_usb(struct at91_pmc *pmc, const char *name,
         init.ops = &at91sam9n12_usb_ops;
         init.parent_names = &parent_name;
         init.num_parents = 1;
-        init.flags = CLK_SET_RATE_GATE;
+        init.flags = CLK_SET_RATE_GATE | CLK_SET_RATE_PARENT;
 
         usb->hw.init = &init;
         usb->pmc = pmc;