[v2,1/3] clk: imx6q: reset exclusive gates on init

Commit Message

Lucas Stach Nov. 15, 2018, 2:30 p.m. UTC

The exclusive gates may be set up in the wrong way by software running
before the clock driver comes up. In that case the exclusive setup is
locked in its initial state, as the complementary function can't be
activated without disabling the initial setup first.

To avoid this lock situation, reset the exclusive gates to the off
state and allow the kernel to provide the proper setup.

Signed-off-by: Lucas Stach <[e-mail]>
Reviewed-by: Dong Aisheng <[e-mail]>
---
 drivers/clk/imx/clk-imx6q.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

Comments

Stephen Boyd Dec. 10, 2018, 7:41 p.m. UTC | #1

Quoting Lucas Stach (2018-11-15 06:30:26)
> The exclusive gates may be set up in the wrong way by software running
> before the clock driver comes up. In that case the exclusive setup is
> locked in its initial state, as the complementary function can't be
> activated without disabling the initial setup first.
> 
> To avoid this lock situation, reset the exclusive gates to the off
> state and allow the kernel to provide the proper setup.
> 
> Signed-off-by: Lucas Stach <[e-mail]>
> Reviewed-by: Dong Aisheng <[e-mail]>
> ---

Applied to clk-next

Patch

diff --git a/drivers/clk/imx/clk-imx6q.c b/drivers/clk/imx/clk-imx6q.c
index bbe0c60f4d09..59f6a3e087db 100644
--- a/drivers/clk/imx/clk-imx6q.c
+++ b/drivers/clk/imx/clk-imx6q.c
@@ -508,8 +508,12 @@  static void __init imx6q_clocks_init(struct device_node *ccm_node)
 	 * lvds1_gate and lvds2_gate are pseudo-gates.  Both can be
 	 * independently configured as clock inputs or outputs.  We treat
 	 * the "output_enable" bit as a gate, even though it's really just
-	 * enabling clock output.
+	 * enabling clock output. Initially the gate bits are cleared, as
+	 * otherwise the exclusive configuration gets locked in the setup done
+	 * by software running before the clock driver, with no way to change
+	 * it.
 	 */
+	writel(readl(base + 0x160) & ~0x3c00, base + 0x160);
 	clk[IMX6QDL_CLK_LVDS1_GATE] = imx_clk_gate_exclusive("lvds1_gate", "lvds1_sel", base + 0x160, 10, BIT(12));
 	clk[IMX6QDL_CLK_LVDS2_GATE] = imx_clk_gate_exclusive("lvds2_gate", "lvds2_sel", base + 0x160, 11, BIT(13));