Messages in this thread | | | Subject | Re: [PATCH v7 10/42] clk: davinci: New driver for davinci PSC clocks | From | David Lechner <> | Date | Mon, 5 Mar 2018 11:46:46 -0600 |
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On 03/05/2018 10:23 AM, David Lechner wrote: > On 03/05/2018 07:02 AM, Bartosz Golaszewski wrote: >> 2018-03-01 17:44 GMT+01:00 David Lechner <david@lechnology.com>: >>> On 03/01/2018 02:36 AM, Bartosz Golaszewski wrote: >>>> >>>> 2018-02-28 22:40 GMT+01:00 David Lechner <david@lechnology.com>: >>>>> >>>>> On 02/28/2018 06:38 AM, Bartosz Golaszewski wrote: >>>>>> >>>>>> >>>>>> >>>>>> I think I found the reason for the strange crashes we were >>>>>> experiencing (emac core->name being NULL) thanks to Sekhar who pointed >>>>>> me in the right direction. >>>>>> >>>>>> The mdio driver fails to probe with v7 due to the supplied clock rate >>>>>> being wrong. Before failing we register the emac clock with >>>>>> pm_clk_add_clk(). When clock_ops puts the clock, it decreases the >>>>>> reference count of the clock, but we never actually increased it in >>>>>> the first place in the line above. The core clock code then destroys >>>>>> the associated clk_core structure. When the next user comes around (in >>>>>> our case the clk debug functions) the system crashes. >>>>>> >>>>>> I believe there to be two issues: one is with v7 - we need to increase >>>>>> the clock reference count in davinci_psc_genpd_attach_dev(). >>>>>> >>>>>> Second is the error path in the clock framework - we should remove the >>>>>> destroyed clk_core from the debug list, which is not being done now. >>>>>> >>>>>> Why we even need to track the refcount of clk_core is a mistery for me >>>>>> though. Stephen, Mike? >>>>>> >>>>>> Best regards, >>>>>> Bartosz Golaszewski >>>>> >>>>> >>>>> >>>>> Great find. I figured it had to be something like this, but I wasn't >>>>> able to reproduce the problem yet. >>>>> >>>>> I suppose it is time to spin up a v8 with some fixes. >>>> >>>> >>>> I still don't know why the mdio clock rate is much lower than in >>>> mainline though. Any ideas? >>>> >>>> Thanks, >>>> Bart >>>> >>> >>> Now that you have fixed the crash, can you answer the questions I have >>> asked earlier? >>> >>>> Can you post the output of this command so that I can see how your >>> >>> clocks are setup: >>> >>> cat /sys/kernel/debug/clk/clk_summary >>> >>>> Using your workaround, can you run: >>> >>> >>> cat /sys/kernel/debug/pm_genpd/pm_genpd_summary >>> >>> If you see: >>> 1e27000.clock-controller: emac off-0 >>> >>> then genpd is not working like it is supposed to. You should see something >>> like this for device that are working: >>> 1e27000.clock-controller: uart2 on >>> /devices/platform/soc@1c00000/1d0d000.serial active >> >> Hi David, Sekhar, >> >> I tried booting the board today over tftp but didn't succeed. I then >> switched to a normal boot from SD card and the boot process froze at >> the same moment (right after the DHCP config, or after rtc config if I >> disabled DHCP in bootargs). I then realized that the emac clock can't >> be the culprit. After some digging I found out that the late_initcall >> to clk_disable_unused() disables sysclk6 - the parent of the arm >> clock, which of course freezes the device. >> >> If I remove the call to clk_disable_unused(), I can boot just fine. >> >> The following other clocks are disabled before pll0_sysclk6: >> pll1_sysclk3 >> pll0_obsclk >> pll0_sysclk7 >> >> davinci_lpsc_clk_enable() is never called for these clocks - in fact >> it's not called for any parent that's not explicitly defined in >> psc-da850.c - I believe this may be one of the reasons. I will get >> back to debugging it tomorrow. >> >> Best regards, >> Bartosz Golaszewski >> > > Thanks for continuing to dig into this. I think I know what needs to > be done now. I think I don't have the dependencies quite right where > the PSC clocks are being registered before the PLL clocks, in which > case they aren't getting the correct parent clock. >
Bartosz,
One more thing to check: I think I had some typos in da850.dtsi where I wrote clock_names instead of clock-names. Please make sure this is fixed in your working branch.
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