clk: ti: omap5+: dpll: implement errata i810

Errata i810 states that DPLL controller can get stuck while transitioning
to a power saving state, while its M/N ratio is being re-programmed.

As a workaround, before re-programming the M/N ratio, SW has to ensure
the DPLL cannot start an idle state transition. SW can disable DPLL
idling by setting the DPLL AUTO_DPLL_MODE=0 or keeping a clock request
active by setting a dependent clock domain in SW_WKUP.

This errata impacts OMAP5 and DRA7 chips, so enable the errata for these.

Signed-off-by: Tero Kristo <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

arch/arm/mach-omap2/clock.c

···
 	if (omap_rev() == OMAP3430_REV_ES1_0)
 		features.flags |= TI_CLK_DPLL4_DENY_REPROGRAM;
 
+	/* Errata I810 for omap5 / dra7 */
+	if (soc_is_omap54xx() || soc_is_dra7xx())
+		features.flags |= TI_CLK_ERRATA_I810;
+
 	ti_clk_setup_features(&features);
 }

drivers/clk/ti/dpll3xxx.c

···
 static int omap3_noncore_dpll_program(struct clk_hw_omap *clk, u16 freqsel)
 {
 	struct dpll_data *dd = clk->dpll_data;
-	u8 dco, sd_div;
+	u8 dco, sd_div, ai = 0;
 	u32 v;
+	bool errata_i810;
 
 	/* 3430 ES2 TRM: 4.7.6.9 DPLL Programming Sequence */
 	_omap3_noncore_dpll_bypass(clk);
···
 		v |= sd_div << __ffs(dd->sddiv_mask);
 	}
 
+	/*
+	 * Errata i810 - DPLL controller can get stuck while transitioning
+	 * to a power saving state. Software must ensure the DPLL can not
+	 * transition to a low power state while changing M/N values.
+	 * Easiest way to accomplish this is to prevent DPLL autoidle
+	 * before doing the M/N re-program.
+	 */
+	errata_i810 = ti_clk_get_features()->flags & TI_CLK_ERRATA_I810;
+
+	if (errata_i810) {
+		ai = omap3_dpll_autoidle_read(clk);
+		if (ai) {
+			omap3_dpll_deny_idle(clk);
+
+			/* OCP barrier */
+			omap3_dpll_autoidle_read(clk);
+		}
+	}
+
 	ti_clk_ll_ops->clk_writel(v, dd->mult_div1_reg);
 
 	/* Set 4X multiplier and low-power mode */
···
 	/* REVISIT: Set ramp-up delay? */
 
 	_omap3_noncore_dpll_lock(clk);
+
+	if (errata_i810 && ai)
+		omap3_dpll_allow_idle(clk);
 
 	return 0;
 }

include/linux/clk/ti.h

···
 #define TI_CLK_DPLL_HAS_FREQSEL			BIT(0)
 #define TI_CLK_DPLL4_DENY_REPROGRAM		BIT(1)
 #define TI_CLK_DISABLE_CLKDM_CONTROL		BIT(2)
+#define TI_CLK_ERRATA_I810			BIT(3)
 
 void ti_clk_setup_features(struct ti_clk_features *features);
 const struct ti_clk_features *ti_clk_get_features(void);