From: Stephen Warren <swarren@xxxxxxxxxx> For a little over a year, U-Boot has configured the flow controller to perform automatic RAM re-repair on off->on power transitions of the CPU rail1]. This is mandatory for correct operation of Tegra124. However, RAM re-repair relies on certain clocks, which the kernel must enable and leave running. PLLP is one of those clocks. This clock is shut down during LP1 in order to save power. Enable bypass (which I believe routes osc_div_clk, essentially the crystal clock, to the PLL output) so that this clock signal toggles even though the PLL is not active. This is required so that LP1 power mode (system suspend) operates correctly. The bypass configuration must then be undone when resuming from LP1, so that all peripheral clocks run at the expected rate. Without this, many peripherals won't work correctly; for example, the UART baud rate would be incorrect. NVIDIA's downstream kernel code only does this if not compiled for Tegra30, so the added code is made conditional upon the chip ID. NVIDIA's downstream code makes this change conditional upon the active CPU cluster. The upstream kernel currently doesn't support cluster switching, so this patch doesn't test the active CPU cluster ID. [1] 3cc7942a4ae5 ARM: tegra: implement RAM repair Reported-by: Jonathan Hunter <jonathanh@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Stephen Warren <swarren@xxxxxxxxxx> --- arch/arm/mach-tegra/sleep-tegra30.S | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/arm/mach-tegra/sleep-tegra30.S b/arch/arm/mach-tegra/sleep-tegra30.S index b408fa56eb89..6922dd8d3e2d 100644 --- a/arch/arm/mach-tegra/sleep-tegra30.S +++ b/arch/arm/mach-tegra/sleep-tegra30.S @@ -370,6 +370,14 @@ _pll_m_c_x_done: pll_locked r1, r0, CLK_RESET_PLLC_BASE pll_locked r1, r0, CLK_RESET_PLLX_BASE + tegra_get_soc_id TEGRA_APB_MISC_BASE, r1 + cmp r1, #TEGRA30 + beq 1f + ldr r1, [r0, #CLK_RESET_PLLP_BASE] + bic r1, r1, #(1<<31) @ disable PllP bypass + str r1, [r0, #CLK_RESET_PLLP_BASE] +1: + mov32 r7, TEGRA_TMRUS_BASE ldr r1, [r7] add r1, r1, #LOCK_DELAY @@ -630,7 +638,10 @@ tegra30_switch_cpu_to_clk32k: str r0, [r4, #PMC_PLLP_WB0_OVERRIDE] /* disable PLLP, PLLA, PLLC and PLLX */ + tegra_get_soc_id TEGRA_APB_MISC_BASE, r1 + cmp r1, #TEGRA30 ldr r0, [r5, #CLK_RESET_PLLP_BASE] + orrne r0, r0, #(1 << 31) @ enable PllP bypass on fast cluster bic r0, r0, #(1 << 30) str r0, [r5, #CLK_RESET_PLLP_BASE] ldr r0, [r5, #CLK_RESET_PLLA_BASE] -- 2.23.0
