On 08/24, Doug Anderson wrote: > Heiko > > On Wed, Aug 19, 2015 at 6:06 AM, Heiko Stuebner <heiko at sntech.de> wrote: > > The structure is xin24m -> pll -> pll-mux (xin24m,pll,xin32k). The pll > > does have an init callback to make sure the boot-selected frequency is > > using the expected pll settings and resets the same frequency using > > the values provided in the driver if necessary. > > > > The setting itself also involves remuxing the pll-mux temporarily to > > the xin24m source to let the new pll rate settle. Until now this worked > > flawlessly, even when it had the flaw of accessing the mux settings > > before the mux actually got registered. > > > > With the recent clock-core conversions this flaw became apparent in > > null pointer dereference in > > [<c03fc400>] (clk_hw_get_num_parents) from [<c0400df0>] (clk_mux_get_parent+0x14/0xc8) > > [<c0400ddc>] (clk_mux_get_parent) from [<c040246c>] (rockchip_rk3066_pll_set_rate+0xd8/0x320) > > > > So to fix that, simply register the pll-mux before the pll, so that > > it will be fully initialized when the pll clock executes its init- > > callback and possibly touches the pll-mux clock. > > > > Signed-off-by: Heiko Stuebner <heiko at sntech.de> > > --- > > This only surfaced with the clk_core changes for 4.3, so should > > probably just go on top. > > > > drivers/clk/rockchip/clk-pll.c | 63 +++++++++++++++++++++--------------------- > > 1 file changed, 32 insertions(+), 31 deletions(-) > > Fixes boot crash on rk3288-veyron-jerry on next-20150824. It'd be > super great to get this landed somewhere so that we can boot linuxnext > again. :) > > Tested-by: Douglas Anderson <dianders at chromium.org> So I understand the fix, but how could it have ever possibly worked flawlessly? clk_mux_get_parent() should have returned -EINVAL through that u8 which would have meant that the check in rockchip_rk3066_pll_set_rate() for cur_parent == PLL_MODE_NORM would never have been true, and we would never have switched the PLL mux over. I guess we've been getting away with this because we don't need to actually switch the mux at this time? -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
