On 15/10/2018 14:12, Marek Szyprowski wrote: > Hi All, > > On 2018-10-08 15:17, Marc Zyngier wrote: >> + Mark Rutland >> >> Hi Marek, >> >> On 08/10/18 13:50, Marek Szyprowski wrote: >>> Use common infrastructure for ARM Architected Timers erratum to enable >>> support for systems with broken CPU firmware (timer registers not >>> properly configured). This mode has been already availabled on ARM >>> (32bits) architecture. This enables to run Linux kernel on ARM64 boards >>> using physical architected timers instead of the virtual ones. Examples >>> of such system with broken firmware are Samsung Exynos5433 SoC based >>> TM2(e) boards, which is already deployed for years and updating firmware >>> is not possible. >>> >>> Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com> >>> --- >>> drivers/clocksource/Kconfig | 11 +++++++++++ >>> drivers/clocksource/arm_arch_timer.c | 15 ++++++++++++--- >>> 2 files changed, 23 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig >>> index a11f4ba98b05..a30752579b03 100644 >>> --- a/drivers/clocksource/Kconfig >>> +++ b/drivers/clocksource/Kconfig >>> @@ -364,6 +364,17 @@ config ARM64_ERRATUM_858921 >>> The workaround will be dynamically enabled when an affected >>> core is detected. >>> +config ARCH_TIMER_REGISTERS_NOT_FW_CONFIGURED >>> + bool "Workaround for arch timer registers not configured by >>> firmware" >>> + default y >>> + select ARM_ARCH_TIMER_OOL_WORKAROUND >>> + depends on ARM_ARCH_TIMER && ARM64 >>> + help >>> + This option enables a workaround for boards, on which arch timer >>> + registers are not properly configured by the board firmware. >>> + The workaround will be dynamically enabled when an affected >>> + board is detected. >>> + >> >> I'm sorry, but I'm strongly pushing back on this. >> >> This horrible hack was accepted with the express condition that it >> would be limited to ARMv7 platforms (on the ground that we never >> really documented the arch timer boot requirements on that version of >> the architecture), and would never proliferate on arm64. From day 1, >> we established what the boot protocol was, and we mandated that either: >> >> - kernel is entered at EL2 on all CPUs >> - cntvoff_el2 is zeroed on all CPUs >> >> and we've got most people to fix their firmware, or live with the >> consequences. If these machines cannot receive a non-broken firmware, >> what are the odds that they will receive a mainline kernel? > > Well, I know that the firmware is broken, but I cannot do anything about it. > On the other hand updating kernel is still possible and mainline runs fine > on TM2(e) boards. I will send v2 without this patch then.
I second Marc's opinion. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
