[PATCH 06/13] clk: qcom: cpu-8996: simplify the cpu_clk_notifier_cb

Dmitry Baryshkov
2023-01-11T19:20:26Z

- Do not use the Alt PLL completely. Switch to smux when necessary to
prevent overvolting
- Restore the parent in case the rate change aborts for some reason
- Do not duplicate resetting the parent in set_parent operation.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
drivers/clk/qcom/clk-cpu-8996.c | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/clk/qcom/clk-cpu-8996.c b/drivers/clk/qcom/clk-cpu-8996.c
index 7e5246ca7e7f..ee7e18b37832 100644
--- a/drivers/clk/qcom/clk-cpu-8996.c
+++ b/drivers/clk/qcom/clk-cpu-8996.c
@@ -506,27 +506,34 @@ static int cpu_clk_notifier_cb(struct notifier_block *nb, unsigned long event,
{
struct clk_cpu_8996_pmux *cpuclk = to_clk_cpu_8996_pmux_nb(nb);
struct clk_notifier_data *cnd = data;
- int ret;

switch (event) {
case PRE_RATE_CHANGE:
- ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw, ALT_INDEX);
qcom_cpu_clk_msm8996_acd_init(base);
+
+ /*
+ * Avoid overvolting. clk_core_set_rate_nolock() walks from top
+ * to bottom, so it will change the rate of the PLL before
+ * chaging the parent of PMUX. This can result in pmux getting
+ * clocked twice the expected rate.
+ *
+ * Manually switch to PLL/2 here.
+ */
+ if (cnd->new_rate < DIV_2_THRESHOLD &&
+ cnd->old_rate > DIV_2_THRESHOLD)
+ clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw, SMUX_INDEX);
+
break;
- case POST_RATE_CHANGE:
- if (cnd->new_rate < DIV_2_THRESHOLD)
- ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw,
- SMUX_INDEX);
- else
- ret = clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw,
- ACD_INDEX);
- break;
+ case ABORT_RATE_CHANGE:
+ /* Revert manual change */
+ if (cnd->new_rate < DIV_2_THRESHOLD &&
+ cnd->old_rate > DIV_2_THRESHOLD)
+ clk_cpu_8996_pmux_set_parent(&cpuclk->clkr.hw, ACD_INDEX);
default:
- ret = 0;
break;
}

- return notifier_from_errno(ret);
+ return NOTIFY_OK;
};

static int qcom_cpu_clk_msm8996_driver_probe(struct platform_device *pdev)
--
2.30.2