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Message-ID: <112d386d29e4bf0869c0ed6f4a1929bdcbb106af.camel@mediatek.com>
Date: Thu, 27 Apr 2023 06:07:29 +0000
From: Chun-Hung Wu (巫駿宏)
<Chun-hung.Wu@...iatek.com>
To: "corbet@....net" <corbet@....net>,
"maz@...nel.org" <maz@...nel.org>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
"angelogioacchino.delregno@...labora.com"
<angelogioacchino.delregno@...labora.com>,
"mark.rutland@....com" <mark.rutland@....com>,
"catalin.marinas@....com" <catalin.marinas@....com>,
"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
Walter Chang (張維哲)
<Walter.Chang@...iatek.com>, "will@...nel.org" <will@...nel.org>
CC: "linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
wsd_upstream <wsd_upstream@...iatek.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Stanley Chu (朱原陞)
<stanley.chu@...iatek.com>,
Freddy Hsin (辛恒豐)
<Freddy.Hsin@...iatek.com>,
"linux-mediatek@...ts.infradead.org"
<linux-mediatek@...ts.infradead.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH] clocksource/drivers/arm_arch_timer: Add workaround for
MediaTek MMIO timer
On Mon, 2023-04-17 at 17:06 +0800, walter.chang@...iatek.com wrote:
> From: Walter Chang <walter.chang@...iatek.com>
>
> The MT69XX series SoCs have the incomplete implementation issue in
> the
> mmio timer. Specifically, the hardware only implements the TVAL
> functionality, but not the CVAL functionality. This hardware
> limitation
> will cause set_next_event_mem() fail to set the actual expiration
> time
> when writing a value to the CVAL. On these platforms, the mmio
> timer's
> internal expiration time will still be judged as 0 (the value of
> TVAL),
> resulting in the mmio timer not functioning as intended.
>
> The workaround is to use TVAL in addition to CVAL for these affected
> platforms.
>
> Signed-off-by: Walter Chang <walter.chang@...iatek.com>
Reviewed-by: Chun-Hung Wu <chun-hung.wu@...iatek.com>
> ---
> Documentation/arm64/silicon-errata.rst | 4 ++++
> drivers/clocksource/Kconfig | 9 ++++++++
> drivers/clocksource/arm_arch_timer.c | 29
> ++++++++++++++++++++++++++
> 3 files changed, 42 insertions(+)
>
> diff --git a/Documentation/arm64/silicon-errata.rst
> b/Documentation/arm64/silicon-errata.rst
> index ec5f889d7681..ca1893713a4c 100644
> --- a/Documentation/arm64/silicon-errata.rst
> +++ b/Documentation/arm64/silicon-errata.rst
> @@ -209,3 +209,7 @@ stable kernels.
> +----------------+-----------------+-----------------+------------
> -----------------+
> | Fujitsu | A64FX | E#010001 |
> FUJITSU_ERRATUM_010001 |
> +----------------+-----------------+-----------------+------------
> -----------------+
> +
> ++----------------+-----------------+-----------------+------------
> -----------------+
> +| MediaTek | MT69XX series | #690001 |
> MEDIATEK_ERRATUM_690001 |
> ++----------------+-----------------+-----------------+------------
> -----------------+
> diff --git a/drivers/clocksource/Kconfig
> b/drivers/clocksource/Kconfig
> index 5fc8f0e7fb38..475356b8dbdc 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -368,6 +368,15 @@ config SUN50I_ERRATUM_UNKNOWN1
> the Allwinner A64 SoC. The workaround will only be active if
> the
> allwinner,erratum-unknown1 property is found in the timer
> node.
>
> +config MEDIATEK_ERRATUM_690001
> + bool "Workaround for MediaTek MT69XX erratum 690001"
> + depends on ARM_ARCH_TIMER && ARM64
> + help
> + This option enables a workaround for incomplete
> implementation
> + in the MMIO timer on the MediaTek MT69XX SoCs. The workaround
> + will only be active if mediatek,erratum-690001 property is
> + found in the timer node.
> +
> config ARM_GLOBAL_TIMER
> bool "Support for the ARM global timer" if COMPILE_TEST
> select TIMER_OF if OF
> diff --git a/drivers/clocksource/arm_arch_timer.c
> b/drivers/clocksource/arm_arch_timer.c
> index e09d4427f604..920570d57fc0 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -389,6 +389,10 @@ static u64 notrace
> sun50i_a64_read_cntvct_el0(void)
> }
> #endif
>
> +#ifdef CONFIG_MEDIATEK_ERRATUM_690001
> +static bool arch_timer_mem_sne_use_tval __ro_after_init;
> +#endif
> +
> #ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
> DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *,
> timer_unstable_counter_workaround);
> EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
> @@ -783,6 +787,19 @@ static __always_inline void
> set_next_event_mem(const int access, unsigned long e
> cnt = arch_counter_get_cnt_mem(timer, CNTPCT_LO);
>
> arch_timer_reg_write(access, ARCH_TIMER_REG_CVAL, evt + cnt,
> clk);
> +#ifdef CONFIG_MEDIATEK_ERRATUM_690001
> + if (arch_timer_mem_sne_use_tval) {
> + /* Due to the incomplete implementation of mmio timer
> on
> + * specific MediaTek platforms, CVAL has not been
> implemented.
> + * Therefore, the workaround is to use TVAL in addition
> to
> + * CVAL.
> + */
> + if (access == ARCH_TIMER_MEM_VIRT_ACCESS)
> + writel_relaxed(evt, timer->base + 0x38);
> + else
> + writel_relaxed(evt, timer->base + 0x28);
> + }
> +#endif
> arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk);
> }
>
> @@ -878,7 +895,16 @@ static void __arch_timer_setup(unsigned type,
> arch_timer_set_next_event_phys_mem;
> }
>
> +#ifdef CONFIG_MEDIATEK_ERRATUM_690001
> + if (arch_timer_mem_sne_use_tval) {
> + pr_info("Enabling mediatek,erratum-690001 for
> mmio timer\n");
> + max_delta = CLOCKSOURCE_MASK(31);
> + } else {
> + max_delta = CLOCKSOURCE_MASK(56);
> + }
> +#else
> max_delta = CLOCKSOURCE_MASK(56);
> +#endif
> }
>
> clk->set_state_shutdown(clk);
> @@ -1591,6 +1617,9 @@ static int __init arch_timer_mem_of_init(struct
> device_node *np)
> frame->valid = true;
> }
>
> +#ifdef CONFIG_MEDIATEK_ERRATUM_690001
> + arch_timer_mem_sne_use_tval = of_property_read_bool(np,
> "mediatek,erratum-690001");
> +#endif
> frame = arch_timer_mem_find_best_frame(timer_mem);
> if (!frame) {
> pr_err("Unable to find a suitable frame in timer @
> %pa\n",
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