Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 15 Feb 2023 14:30:51 +0100 | Subject | Re: [PATCH v2 4/4] clocksource/drivers/timer-mediatek: Make timer-mediatek become loadable module | From | AngeloGioacchino Del Regno <> |
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Il 15/02/23 14:18, Sudeep Holla ha scritto: > On Wed, Feb 15, 2023 at 01:43:19PM +0100, AngeloGioacchino Del Regno wrote: >> Il 14/02/23 23:20, Sudeep Holla ha scritto: >>> On Tue, Feb 14, 2023 at 06:53:14PM +0800, walter.chang@mediatek.com wrote: >>>> From: Chun-Hung Wu <chun-hung.wu@mediatek.com> >>>> >>>> Make the timer-mediatek driver which can register >>>> an always-on timer as tick_broadcast_device on >>>> MediaTek SoCs become loadable module in GKI. >>>> >>>> Signed-off-by: Chun-Hung Wu <chun-hung.wu@mediatek.com> >>>> --- >>>> drivers/clocksource/Kconfig | 2 +- >>>> drivers/clocksource/timer-mediatek.c | 43 ++++++++++++++++++++++++++++ >>>> 2 files changed, 44 insertions(+), 1 deletion(-) >>> >>> [...] >>> >>>> diff --git a/drivers/clocksource/timer-mediatek.c b/drivers/clocksource/timer-mediatek.c >>>> index d5b29fd03ca2..3358758ea694 100644 >>>> --- a/drivers/clocksource/timer-mediatek.c >>>> +++ b/drivers/clocksource/timer-mediatek.c >>> >>> [...] >>> >>>> +static const struct of_device_id mtk_timer_match_table[] = { >>>> + { >>>> + .compatible = "mediatek,mt6577-timer", >>>> + .data = mtk_gpt_init, >>>> + }, >>>> + { >>>> + .compatible = "mediatek,mt6765-timer", >>>> + .data = mtk_syst_init, >>>> + }, >>>> + { >>>> + .compatible = "mediatek,mt6795-systimer", >>>> + .data = mtk_cpux_init, >>>> + }, >>>> + {} >>>> +}; >>>> + >>>> +static struct platform_driver mtk_timer_driver = { >>>> + .probe = mtk_timer_probe, >>>> + .driver = { >>>> + .name = "mtk-timer", >>>> + .of_match_table = mtk_timer_match_table, >>>> + }, >>>> +}; >>>> +module_platform_driver(mtk_timer_driver); >>>> + >>>> +MODULE_DESCRIPTION("MediaTek Module Timer driver"); >>>> +MODULE_LICENSE("GPL v2"); >>>> +#else >>>> TIMER_OF_DECLARE(mtk_mt6577, "mediatek,mt6577-timer", mtk_gpt_init); >>>> TIMER_OF_DECLARE(mtk_mt6765, "mediatek,mt6765-timer", mtk_syst_init); >>>> TIMER_OF_DECLARE(mtk_mt6795, "mediatek,mt6795-systimer", mtk_cpux_init); >>> >>> Why do you need these ? If this driver can work as a module, it can be >>> built-in module and doesn't need to be initialised early using of_timer_init >>> (can't recall the exact name) >>> >> >> Some platforms need early initialization; this is seen on ones for which the >> bootloader does not initialize the "CPUXGPT" timer, which is used as the ARM >> arch timer. (No, on those platforms you can't upgrade the bootloader, as it's >> signed with a OEM key which is not obtainable, and signature verified earlier >> in the bootchain). >> > > Is this arm32 or arm64 platform? Do you mean that these platforms don't have > working architected timers ? >
Both. I mean that these platforms do have architected timers, but they are stopped before the bootloader jumps to the kernel, or they are never started at all.
Please refer to:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/clocksource/timer-mediatek.c?h=next-20230215&id=327e93cf9a59b0d04eb3a31a7fdbf0f11cf13ecb
For a nice explanation.
> Quick grep suggests the below list of platforms/SoC: > > | arch/arm64/boot/dts/mediatek/mt6795.dtsi > | arch/arm64/boot/dts/mediatek/mt8173.dtsi > | arch/arm64/boot/dts/mediatek/mt8183.dtsi > | arch/arm64/boot/dts/mediatek/mt8186.dtsi > | arch/arm64/boot/dts/mediatek/mt8192.dtsi > | arch/arm64/boot/dts/mediatek/mt8195.dtsi > | arch/arm64/boot/dts/mediatek/mt8516.dtsi > | arch/arm/boot/dts/mt7623.dtsi > | arch/arm/boot/dts/mt7629.dtsi > | arch/arm/boot/dts/mt8127.dtsi > | arch/arm/boot/dts/mt8135.dtsi > > All the above has architected timers and can have the other timer initialised > at module_initcall level. > > | arch/arm/boot/dts/mt2701.dtsi > | arch/arm/boot/dts/mt6580.dtsi > | arch/arm/boot/dts/mt6582.dtsi > | arch/arm/boot/dts/mt6589.dtsi > | arch/arm/boot/dts/mt6592.dtsi > > The above ones have cortex-a7 but still don't have architected timers listed > in the DT. Anyways all use "mediatek,mt6577-timer", so except that other > 2 can be dropped from the else and force them to be initialised later. > >> As a matter of fact (and somehow obvious), on those platforms (for example, >> MT6795.. but many other as well, really), you *need* this driver to be >> built-in and, well, initialize the CPUX timer as early as possible :-) >> > > Built-in is not a problem, you can still remove TIMER_OF_DECLARE as > the initialisation happens later at module_initcall level. >
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