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Subject[PATCH v6 03/12] clk: tegra: cclk: Add helpers for handling PLLX rate changes
Date
CCLK should be re-parented away from PLLX if PLLX's rate is changing.
The PLLP parent is a common safe CPU parent for all Tegra SoCs, thus
CCLK will be re-parented to PLLP before PLLX rate-change begins and then
switched back to PLLX after the rate-change completion. This patch adds
helper functions which perform CCLK re-parenting, these helpers will be
utilized by further patches.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/clk/tegra/clk-tegra-super-cclk.c | 34 ++++++++++++++++++++++++
drivers/clk/tegra/clk.h | 2 ++
2 files changed, 36 insertions(+)

diff --git a/drivers/clk/tegra/clk-tegra-super-cclk.c b/drivers/clk/tegra/clk-tegra-super-cclk.c
index 7bcb9e8d0860..a03119c30456 100644
--- a/drivers/clk/tegra/clk-tegra-super-cclk.c
+++ b/drivers/clk/tegra/clk-tegra-super-cclk.c
@@ -25,6 +25,9 @@

#define SUPER_CDIV_ENB BIT(31)

+static struct tegra_clk_super_mux *cclk_super;
+static bool cclk_on_pllx;
+
static u8 cclk_super_get_parent(struct clk_hw *hw)
{
return tegra_clk_super_ops.get_parent(hw);
@@ -115,6 +118,9 @@ struct clk *tegra_clk_register_super_cclk(const char *name,
struct clk_init_data init;
u32 val;

+ if (WARN_ON(cclk_super))
+ return ERR_PTR(-EBUSY);
+
super = kzalloc(sizeof(*super), GFP_KERNEL);
if (!super)
return ERR_PTR(-ENOMEM);
@@ -173,6 +179,34 @@ struct clk *tegra_clk_register_super_cclk(const char *name,
clk = clk_register(NULL, &super->hw);
if (IS_ERR(clk))
kfree(super);
+ else
+ cclk_super = super;

return clk;
}
+
+int tegra_cclk_pre_pllx_rate_change(void)
+{
+ if (IS_ERR_OR_NULL(cclk_super))
+ return -EINVAL;
+
+ if (cclk_super_get_parent(&cclk_super->hw) == PLLX_INDEX)
+ cclk_on_pllx = true;
+ else
+ cclk_on_pllx = false;
+
+ /*
+ * CPU needs to be temporarily re-parented away from PLLX if PLLX
+ * changes its rate. PLLP is a safe parent for CPU on all Tegra SoCs.
+ */
+ if (cclk_on_pllx)
+ cclk_super_set_parent(&cclk_super->hw, PLLP_INDEX);
+
+ return 0;
+}
+
+void tegra_cclk_post_pllx_rate_change(void)
+{
+ if (cclk_on_pllx)
+ cclk_super_set_parent(&cclk_super->hw, PLLX_INDEX);
+}
diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
index fa18bef914af..0afe28f4372b 100644
--- a/drivers/clk/tegra/clk.h
+++ b/drivers/clk/tegra/clk.h
@@ -771,6 +771,8 @@ struct clk *tegra_clk_register_super_cclk(const char *name,
const char * const *parent_names, u8 num_parents,
unsigned long flags, void __iomem *reg, u8 clk_super_flags,
spinlock_t *lock);
+int tegra_cclk_pre_pllx_rate_change(void);
+void tegra_cclk_post_pllx_rate_change(void);

/**
* struct tegra_sdmmc_mux - switch divider with Low Jitter inputs for SDMMC
--
2.24.0
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