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Subject[PATCH v1 3/4] clk: tegra20: Turn EMC clock gate into divider
Date
Kernel should never gate the EMC clock as it causes immediate lockup, so
removing clk-gate functionality doesn't affect anything. Turning EMC clk
gate into divider allows to implement glitch-less EMC scaling, avoiding
reparenting to a backup clock.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
drivers/clk/tegra/clk-tegra20.c | 39 ++++++++++++++++++++++++---------
1 file changed, 29 insertions(+), 10 deletions(-)

diff --git a/drivers/clk/tegra/clk-tegra20.c b/drivers/clk/tegra/clk-tegra20.c
index cc857d4d4a86..189dbc86ab71 100644
--- a/drivers/clk/tegra/clk-tegra20.c
+++ b/drivers/clk/tegra/clk-tegra20.c
@@ -578,7 +578,6 @@ static struct tegra_clk tegra20_clks[tegra_clk_max] __initdata = {
[tegra_clk_afi] = { .dt_id = TEGRA20_CLK_AFI, .present = true },
[tegra_clk_fuse] = { .dt_id = TEGRA20_CLK_FUSE, .present = true },
[tegra_clk_kfuse] = { .dt_id = TEGRA20_CLK_KFUSE, .present = true },
- [tegra_clk_emc] = { .dt_id = TEGRA20_CLK_EMC, .present = true },
};

static unsigned long tegra20_clk_measure_input_freq(void)
@@ -799,19 +798,18 @@ static struct tegra_periph_init_data tegra_periph_nodiv_clk_list[] = {
TEGRA_INIT_DATA_NODIV("disp2", mux_pllpdc_clkm, CLK_SOURCE_DISP2, 30, 2, 26, 0, TEGRA20_CLK_DISP2),
};

-static void __init tegra20_periph_clk_init(void)
+static void __init tegra20_emc_clk_init(void)
{
- struct tegra_periph_init_data *data;
+ u32 emc_reg = readl_relaxed(clk_base + CLK_SOURCE_EMC);
+ u32 use_pllm_ud = BIT(29);
struct clk *clk;
- unsigned int i;

- /* ac97 */
- clk = tegra_clk_register_periph_gate("ac97", "pll_a_out0",
- TEGRA_PERIPH_ON_APB,
- clk_base, 0, 3, periph_clk_enb_refcnt);
- clks[TEGRA20_CLK_AC97] = clk;
+ if (emc_reg & use_pllm_ud) {
+ pr_err("%s: un-divided PllM_out0 used as clock source\n",
+ __func__);
+ return;
+ }

- /* emc */
clk = clk_register_mux(NULL, "emc_mux", mux_pllmcp_clkm,
ARRAY_SIZE(mux_pllmcp_clkm),
CLK_SET_RATE_NO_REPARENT,
@@ -822,6 +820,27 @@ static void __init tegra20_periph_clk_init(void)
&emc_lock);
clks[TEGRA20_CLK_MC] = clk;

+ clk = clk_register_divider(NULL, "emc", "emc_mux", CLK_IS_CRITICAL,
+ clk_base + CLK_SOURCE_EMC, 0, 7,
+ 0, &emc_lock);
+ clks[TEGRA20_CLK_EMC] = clk;
+}
+
+static void __init tegra20_periph_clk_init(void)
+{
+ struct tegra_periph_init_data *data;
+ struct clk *clk;
+ unsigned int i;
+
+ /* ac97 */
+ clk = tegra_clk_register_periph_gate("ac97", "pll_a_out0",
+ TEGRA_PERIPH_ON_APB,
+ clk_base, 0, 3, periph_clk_enb_refcnt);
+ clks[TEGRA20_CLK_AC97] = clk;
+
+ /* emc */
+ tegra20_emc_clk_init();
+
/* dsi */
clk = tegra_clk_register_periph_gate("dsi", "pll_d", 0, clk_base, 0,
48, periph_clk_enb_refcnt);
--
2.17.0
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