[PATCH v2] clk: qcom: Properly change rates for ahbix clock

Stephen Boyd
2015-03-06T23:41:58Z

The ahbix clock can never be turned off in practice. To change the
rates we need to switch the mux off the M/N counter to an always on
source (XO), reprogram the M/N counter to get the rate we want and
finally switch back to the M/N counter. Add a new ops structure
for this type of clock so that we can set the rate properly.

Fixes: c99e515a92e9 "clk: qcom: Add IPQ806X LPASS clock controller (LCC) driver"
Cc: Kenneth Westfield <kwestfie@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---

Changes from v1:
* Handle the case where clock feeding M/N counter is off

drivers/clk/qcom/clk-rcg.c | 62 ++++++++++++++++++++++++++++++++++++++++++
drivers/clk/qcom/clk-rcg.h | 1 +
drivers/clk/qcom/lcc-ipq806x.c | 5 ++--
3 files changed, 65 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/qcom/clk-rcg.c b/drivers/clk/qcom/clk-rcg.c
index 0039bd7d3965..466f30ca65c2 100644
--- a/drivers/clk/qcom/clk-rcg.c
+++ b/drivers/clk/qcom/clk-rcg.c
@@ -495,6 +495,57 @@ static int clk_rcg_bypass_set_rate(struct clk_hw *hw, unsigned long rate,
return __clk_rcg_set_rate(rcg, rcg->freq_tbl);
}

+/*
+ * This type of clock has a glitch-free mux that switches between the output of
+ * the M/N counter and an always on clock source (XO). When clk_set_rate() is
+ * called we need to make sure that we don't switch to the M/N counter if it
+ * isn't clocking because the mux will get stuck and the clock will stop
+ * outputting a clock. This can happen if the framework isn't aware that this
+ * clock is on and so clk_set_rate() doesn't turn on the new parent. To fix
+ * this we switch the mux in the enable/disable ops and reprogram the M/N
+ * counter in the set_rate op. We also make sure to switch away from the M/N
+ * counter in set_rate if software thinks the clock is off.
+ */
+static int clk_rcg_lcc_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct clk_rcg *rcg = to_clk_rcg(hw);
+ const struct freq_tbl *f;
+ int ret;
+ u32 gfm = BIT(10);
+
+ f = qcom_find_freq(rcg->freq_tbl, rate);
+ if (!f)
+ return -EINVAL;
+
+ /* Switch to XO to avoid glitches */
+ regmap_update_bits(rcg->clkr.regmap, rcg->ns_reg, gfm, 0);
+ ret = __clk_rcg_set_rate(rcg, f);
+ /* Switch back to M/N if it's clocking */
+ if (__clk_is_enabled(hw->clk))
+ regmap_update_bits(rcg->clkr.regmap, rcg->ns_reg, gfm, gfm);
+
+ return ret;
+}
+
+static int clk_rcg_lcc_enable(struct clk_hw *hw)
+{
+ struct clk_rcg *rcg = to_clk_rcg(hw);
+ u32 gfm = BIT(10);
+
+ /* Use M/N */
+ return regmap_update_bits(rcg->clkr.regmap, rcg->ns_reg, gfm, gfm);
+}
+
+static void clk_rcg_lcc_disable(struct clk_hw *hw)
+{
+ struct clk_rcg *rcg = to_clk_rcg(hw);
+ u32 gfm = BIT(10);
+
+ /* Use XO */
+ regmap_update_bits(rcg->clkr.regmap, rcg->ns_reg, gfm, 0);
+}
+
static int __clk_dyn_rcg_set_rate(struct clk_hw *hw, unsigned long rate)
{
struct clk_dyn_rcg *rcg = to_clk_dyn_rcg(hw);
@@ -543,6 +594,17 @@ const struct clk_ops clk_rcg_bypass_ops = {
};
EXPORT_SYMBOL_GPL(clk_rcg_bypass_ops);

+const struct clk_ops clk_rcg_lcc_ops = {
+ .enable = clk_rcg_lcc_enable,
+ .disable = clk_rcg_lcc_disable,
+ .get_parent = clk_rcg_get_parent,
+ .set_parent = clk_rcg_set_parent,
+ .recalc_rate = clk_rcg_recalc_rate,
+ .determine_rate = clk_rcg_determine_rate,
+ .set_rate = clk_rcg_lcc_set_rate,
+};
+EXPORT_SYMBOL_GPL(clk_rcg_lcc_ops);
+
const struct clk_ops clk_dyn_rcg_ops = {
.enable = clk_enable_regmap,
.is_enabled = clk_is_enabled_regmap,
diff --git a/drivers/clk/qcom/clk-rcg.h b/drivers/clk/qcom/clk-rcg.h
index 687e41f91d7c..d09d06ba278e 100644
--- a/drivers/clk/qcom/clk-rcg.h
+++ b/drivers/clk/qcom/clk-rcg.h
@@ -96,6 +96,7 @@ struct clk_rcg {

extern const struct clk_ops clk_rcg_ops;
extern const struct clk_ops clk_rcg_bypass_ops;
+extern const struct clk_ops clk_rcg_lcc_ops;

#define to_clk_rcg(_hw) container_of(to_clk_regmap(_hw), struct clk_rcg, clkr)

diff --git a/drivers/clk/qcom/lcc-ipq806x.c b/drivers/clk/qcom/lcc-ipq806x.c
index 9e27d82c0201..a6d3a6745c4d 100644
--- a/drivers/clk/qcom/lcc-ipq806x.c
+++ b/drivers/clk/qcom/lcc-ipq806x.c
@@ -386,13 +386,12 @@ static struct clk_rcg ahbix_clk = {
.freq_tbl = clk_tbl_ahbix,
.clkr = {
.enable_reg = 0x38,
- .enable_mask = BIT(10), /* toggle the gfmux to select mn/pxo */
+ .enable_mask = BIT(11),
.hw.init = &(struct clk_init_data){
.name = "ahbix",
.parent_names = lcc_pxo_pll4,
.num_parents = 2,
- .ops = &clk_rcg_ops,
- .flags = CLK_SET_RATE_GATE,
+ .ops = &clk_rcg_lcc_ops,
},
},
};
--
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