On 05.06.2014 20:48, Doug Anderson wrote: > Tomasz / Mike, > > On Fri, May 30, 2014 at 9:32 AM, Doug Anderson <dianders@xxxxxxxxxxxx> wrote: >> Right now if you've got earlyprintk enabled on exynos5420-peach-pit >> then you'll get a hang on boot. Here's why: >> >> 1. The i2c-s3c2410 driver will probe at subsys_initcall. It will >> enable its clock and disable it. This is the clock "i2c2". >> 2. The act of disabling "i2c2" will disable its parents. In this case >> the parent is "aclk66_peric". There are no other children of >> "aclk66_peric" officially enabled, so "aclk66_peric" will be turned >> off (despite being CLK_IGNORE_UNUSED, but that's by design). >> 3. The next time you try to earlyprintk you'll do so without the UART >> clock enabled. That's because the UART clocks are also children of >> "aclk66_peric". You'll hang. >> >> There's no good place to put a clock enable for earlyprintk, which is >> handled by a bunch of assembly code. The best we can do is to handle >> this in the clock driver. >> >> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx> >> Tested-by: Javier Martinez Canillas <javier.martinez@xxxxxxxxxxxxxxx> >> --- >> Changes in v2: >> - Use GATE_A and clk_get(). Save the clock for putting later. >> - Return 0 from exynos5420_clk_late_init(). >> >> drivers/clk/samsung/clk-exynos5420.c | 33 +++++++++++++++++++++++++++++++-- >> 1 file changed, 31 insertions(+), 2 deletions(-) > > Are there other changes you'd like me to make to this? It would be > really nice to get this in for 3.16 so the system doesn't just > mysteriously hang when you use earlyprintk. We can probably take this as an -rc fix, so it should be fine. However I still don't see the point of exporting this clock and polluting the global clkdev namespace. Even the diffstat looks better in v1. Best regards, Tomasz -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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