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 is known to impact OMAP5 and DRA7 chips, but lets enable it unconditionally to avoid any potential problems with earlier generation SoCs also. Signed-off-by: Tero Kristo <[email protected]> --- v2: made the fix to be applied unconditionally on all OMAP3+ SoCs drivers/clk/ti/dpll3xxx.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/drivers/clk/ti/dpll3xxx.c b/drivers/clk/ti/dpll3xxx.c index f4dec00..cb26eb8 100644 --- a/drivers/clk/ti/dpll3xxx.c +++ b/drivers/clk/ti/dpll3xxx.c @@ -305,7 +305,7 @@ static void _lookup_sddiv(struct clk_hw_omap *clk, u8 *sd_div, u16 m, u8 n) 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; /* 3430 ES2 TRM: 4.7.6.9 DPLL Programming Sequence */ @@ -350,6 +350,21 @@ static int omap3_noncore_dpll_program(struct clk_hw_omap *clk, u16 freqsel) 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. + */ + 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 */ @@ -379,6 +394,9 @@ static int omap3_noncore_dpll_program(struct clk_hw_omap *clk, u16 freqsel) _omap3_noncore_dpll_lock(clk); + if (ai) + omap3_dpll_allow_idle(clk); + return 0; } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
