OMAP3: PM: Do not rely on ROM code to restore CM_AUTOIDLE_PLL.AUTO_PERIPH_DPLL
As per OMAP3 erratum (i671), ROM code adds extra latencies while restoring CM_AUTOIDLE_PLL register, if AUTO_PERIPH_DPLL is equal to 1. This patch stores 0's in scratchpad content area corresponding to AUTO_PERIPH_DPLL, to prevent ROM code to try to lock per DPLL, since it won't respect proper programing scheme. This register is then stored in prcm context. The saving and restore is now done by kernel side. Here follow the erratum description DESCRIPTION After OFF mode transition, among many restorations, the ROM Code restores the CM_AUTOIDLE_PLL register, and after that, it tries to relock the PER DPLL. In case the restoration data stored in scratchpad memory contains a field CM_AUTOIDLE_PLL.AUTO_PERIPH_DPLL = 1, then the way the ROM Code restores and locks the PER DPLL does not respect the PER DPLL programming scheme. In that case, the DPLL might not lock. Meanwhile, when trying to lock the PER DPLL, the ROM Code does not hang. Only extra latencies are introduced at wake-up. WORKAROUND When saving the context-restore structure in scratchpad memory, in order to respect the PER DPLL programming scheme, it is advised to store 0 in the CM_AUTOIDLE_PLL.AUTO_PERIPH_DPLL field of the saved structure. After wake-up, the application should store in CM_AUTOIDLE_PLL register the right desired value. Signed-off-by: NEduardo Valentin <eduardo.valentin@ti.com> Signed-off-by: NPaul Walmsley <paul@pwsan.com>
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