clk: tegra: Don't deassert reset on enabling clocks

The Tegra clock driver contains legacy code which deasserts hardware reset
when peripheral clocks are enabled. This behaviour comes from a pre-CCF
era of the Tegra drivers. This is unacceptable for modern kernel drivers
which use generic CCF and reset-control APIs because it breaks assumptions
of the drivers about clk/reset sequences and about reset-propagation
delays. Hence remove the awkward legacy behaviour from the clk driver.

In particular PMC driver assumes that hardware blocks remains in reset
while power domain is turning on, but the clk driver deasserts the reset
before power clamp is removed, hence breaking the driver's assumption.

Signed-off-by: Dmitry Osipenko <[email protected]>
Signed-off-by: Thierry Reding <[email protected]>

Author: digetx

drivers/clk/tegra/clk-periph-gate.c

@@ -55,14 +55,6 @@ static void clk_periph_enable_locked(struct clk_hw *hw)
 	write_enb_set(periph_clk_to_bit(gate), gate);
 	udelay(2);
 
-	if (!(gate->flags & TEGRA_PERIPH_NO_RESET) &&
-	    !(gate->flags & TEGRA_PERIPH_MANUAL_RESET)) {
-		if (read_rst(gate) & periph_clk_to_bit(gate)) {
-			udelay(5); /* reset propogation delay */
-			write_rst_clr(periph_clk_to_bit(gate), gate);
-		}
-	}
-
 	if (gate->flags & TEGRA_PERIPH_WAR_1005168) {
 		writel_relaxed(0, gate->clk_base + LVL2_CLK_GATE_OVRE);
 		writel_relaxed(BIT(22), gate->clk_base + LVL2_CLK_GATE_OVRE);

drivers/clk/tegra/clk-tegra30.c

@@ -1006,7 +1006,7 @@ static struct tegra_periph_init_data tegra_periph_clk_list[] = {
 	TEGRA_INIT_DATA_MUX("dam0", mux_pllacp_clkm, CLK_SOURCE_DAM0, 108, 0, TEGRA30_CLK_DAM0),
 	TEGRA_INIT_DATA_MUX("dam1", mux_pllacp_clkm, CLK_SOURCE_DAM1, 109, 0, TEGRA30_CLK_DAM1),
 	TEGRA_INIT_DATA_MUX("dam2", mux_pllacp_clkm, CLK_SOURCE_DAM2, 110, 0, TEGRA30_CLK_DAM2),
-	TEGRA_INIT_DATA_INT("3d2", mux_pllmcpa, CLK_SOURCE_3D2, 98, TEGRA_PERIPH_MANUAL_RESET, TEGRA30_CLK_GR3D2),
+	TEGRA_INIT_DATA_INT("3d2", mux_pllmcpa, CLK_SOURCE_3D2, 98, 0, TEGRA30_CLK_GR3D2),
 	TEGRA_INIT_DATA_INT("se", mux_pllpcm_clkm, CLK_SOURCE_SE, 127, 0, TEGRA30_CLK_SE),
 	TEGRA_INIT_DATA_MUX8("hdmi", mux_pllpmdacd2_clkm, CLK_SOURCE_HDMI, 51, 0, TEGRA30_CLK_HDMI),
 	TEGRA_INIT_DATA("pwm", NULL, NULL, pwm_parents, CLK_SOURCE_PWM, 28, 2, 0, 0, 8, 1, 0, 17, TEGRA_PERIPH_ON_APB, TEGRA30_CLK_PWM),

drivers/clk/tegra/clk.h

@@ -553,9 +553,6 @@ struct tegra_clk_periph_regs {
  * Flags:
  * TEGRA_PERIPH_NO_RESET - This flag indicates that reset is not allowed
  *     for this module.
- * TEGRA_PERIPH_MANUAL_RESET - This flag indicates not to reset module
- *     after clock enable and driver for the module is responsible for
- *     doing reset.
  * TEGRA_PERIPH_ON_APB - If peripheral is in the APB bus then read the
  *     bus to flush the write operation in apb bus. This flag indicates
  *     that this peripheral is in apb bus.
@@ -577,7 +574,6 @@ struct tegra_clk_periph_gate {
 #define TEGRA_CLK_PERIPH_GATE_MAGIC 0x17760309
 
 #define TEGRA_PERIPH_NO_RESET BIT(0)
-#define TEGRA_PERIPH_MANUAL_RESET BIT(1)
 #define TEGRA_PERIPH_ON_APB BIT(2)
 #define TEGRA_PERIPH_WAR_1005168 BIT(3)
 #define TEGRA_PERIPH_NO_DIV BIT(4)