linux-kernel - Re: [PATCH] clocksource/drivers/timer-mediatek: Split out CPUXGPT timers

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Message-ID: <75a890d1-b3b9-0316-749b-fb2bf80c3176@collabora.com>
Date:   Wed, 29 Mar 2023 15:10:46 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Walter Chang (張維哲) 
        <Walter.Chang@...iatek.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        wsd_upstream <wsd_upstream@...iatek.com>,
        "kernel@...labora.com" <kernel@...labora.com>,
        Chun-Hung Wu (巫駿宏) 
        <Chun-hung.Wu@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Stanley Chu (朱原陞) 
        <stanley.chu@...iatek.com>,
        Freddy Hsin (辛恒豐) 
        <Freddy.Hsin@...iatek.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH] clocksource/drivers/timer-mediatek: Split out CPUXGPT
 timers

Il 29/03/23 09:51, Walter Chang (張維哲) ha scritto:
> On Thu, 2023-03-09 at 11:39 +0100, AngeloGioacchino Del Regno wrote:
>> On MediaTek platforms, CPUXGPT is the source for the AArch64 System
>> Timer, read through CNTVCT_EL0.
>>
>> The handling for starting this timer ASAP was introduced in commit
>> 327e93cf9a59 ("clocksource/drivers/timer-mediatek: Implement CPUXGPT
>> timers")
>> which description also contains an important full explanation of the
>> reasons why this driver is necessary and cannot be a module.
>>
>> In preparation for an eventual conversion of timer-mediatek to a
>> platform_driver that would be possibly built as a module, split out
>> the CPUXGPT timers driver to a new timer-mediatek-cpux.c driver.
>>
>> This commit brings no functional changes.
>>
>> Signed-off-by: AngeloGioacchino Del Regno <
>> angelogioacchino.delregno@...labora.com>
>> ---
>>
>> Note: I've added a mention to the commit that is introducing CPUXGPT
>> because it contains a broad explanation about why this is needed and
>> why it is mandatory to have it as built-in and initialized as early
>> as possible. This is mostly because this question was asked multiple
>> times and I've been pointing people to that commit to explain it all.
>>
>> This commit was made because of a discussion about the impossibility
>> to convert timer-mediatek to a module: even though that's definitely
>> not easy at all, this will make sure that whatever cannot (ever) be
>> built as module goes out of that driver.
>>
>> I tried to tackle a timer-mediatek conversion to platform_driver as
>> well, but I don't currently have the required bandwidth to do so:
>> as a first step I moved that, so I'm pushing this commit as to try
>> to reduce duplicated work.
>>
>> This commit was tested on MT6795 Sony Xperia M5.

..snip..

>> @@ -452,4 +339,3 @@ static int __init mtk_gpt_init(struct device_node
>> *node)
>>   }
>>   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);
> 
> This patch looks good to me. Thanks for assisting us in spliting out
> the CPUX driver.
> 

Hello Walter,

thanks for checking this patch. If you have actually reviewed this one,
you could help the maintainers to know by releasing your Reviewed-by tag
on this patch.

Regards,
Angelo