Hello. My Freescale TWR-MPC5125 board instantly reboots if I touch any physical address on the LocalPlus Bus (LPB) for the first time when Linux has already booted.
This effect is reproduced by using /dev/mem or loading a kernel module which works with any peripherals on LPB. It took me some time to find out that such crash is caused by clk_disable_unused() in drivers/clk/clk.c, which disables LocalPlus Controller (LPC) clock if I don't touch LPB addresses in the previous initcalls. So starting Linux with clk_ignore_unused bootparam or inserting dummy LPB reading to some initcall is a temporary fix. Is it correct to gate LPC clock? If yes, how to avoid the mentioned crashes properly? There's a piece of code in arch/powerpc/platforms/512x/clock-commonclk.c which is doubtful for me: /* * pre-enable those "internal" clock items which never get * claimed by any peripheral driver, to not have the clock * subsystem disable them late at startup */ clk_prepare_enable(clks[MPC512x_CLK_DUMMY]); clk_prepare_enable(clks[MPC512x_CLK_E300]); /* PowerPC CPU */ clk_prepare_enable(clks[MPC512x_CLK_DDR]); /* DRAM */ clk_prepare_enable(clks[MPC512x_CLK_MEM]); /* SRAM */ clk_prepare_enable(clks[MPC512x_CLK_IPS]); /* SoC periph */ clk_prepare_enable(clks[MPC512x_CLK_LPC]); /* boot media */ Does it mean that these clocks should be registered with CLK_IGNORE_UNUSED flag? Thanks a lot. Best regards, Alexander _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
