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Message-ID: <8824147c-5512-a7a5-9e89-60b510111500@gmail.com>
Date:   Thu, 14 Apr 2022 07:14:40 +0900
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Subject: Re: [RFC PATCH 2/2] PM / devfreq: rk3399_dmc: Block PMU during
 transitions
Content-Language: en-US
To:     Brian Norris <briannorris@chromium.org>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Heiko Stuebner <heiko@sntech.de>
Cc:     linux-kernel@vger.kernel.org,
        Elaine Zhang <zhangqing@rock-chips.com>,
        linux-pm@vger.kernel.org, Doug Anderson <dianders@chromium.org>,
        linux-arm-kernel@lists.infradead.org,
        linux-rockchip@lists.infradead.org
References: <20220406014842.2771799-1-briannorris@chromium.org>
 <20220405184816.RFC.2.I2d73b403944f0b8b5871a77585b73f31ccc62999@changeid>
From:   Chanwoo Choi <cwchoi00@gmail.com>
In-Reply-To: <20220405184816.RFC.2.I2d73b403944f0b8b5871a77585b73f31ccc62999@changeid>
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Precedence: bulk

Hi Brian,

On 22. 4. 6. 10:48, Brian Norris wrote:
> See the previous patch ("soc: rockchip: power-domain: Manage resource
> conflicts with firmware") for a thorough explanation of the conflicts.
> While ARM Trusted Firmware may be modifying memory controller and
> power-domain states, we need to block the kernel's power-domain driver.
> 
> If the power-domain driver is disabled, there is no resource conflict
> and this becomes a no-op.
> 
> Signed-off-by: Brian Norris <briannorris@chromium.org>
> ---
> 
>   drivers/devfreq/rk3399_dmc.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/devfreq/rk3399_dmc.c b/drivers/devfreq/rk3399_dmc.c
> index e494d1497d60..daff40702615 100644
> --- a/drivers/devfreq/rk3399_dmc.c
> +++ b/drivers/devfreq/rk3399_dmc.c
> @@ -21,6 +21,7 @@
>   #include <linux/rwsem.h>
>   #include <linux/suspend.h>
>   
> +#include <soc/rockchip/pm_domains.h>
>   #include <soc/rockchip/rk3399_grf.h>
>   #include <soc/rockchip/rockchip_sip.h>
>   
> @@ -93,6 +94,16 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
>   
>   	mutex_lock(&dmcfreq->lock);
>   
> +	/*
> +	 * Ensure power-domain transitions don't interfere with ARM Trusted
> +	 * Firmware power-domain idling.
> +	 */
> +	err = rockchip_pmu_block();
> +	if (err) {
> +		dev_err(dev, "Failed to block PMU: %d\n", err);
> +		goto out_unlock;
> +	}
> +
>   	/*
>   	 * Some idle parameters may be based on the DDR controller clock, which
>   	 * is half of the DDR frequency.
> @@ -198,6 +209,8 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
>   	dmcfreq->volt = target_volt;
>   
>   out:
> +	rockchip_pmu_unblock();
> +out_unlock:
>   	mutex_unlock(&dmcfreq->lock);
>   	return err;
>   }

Acked-by: Chanwoo Choi <cw00.choi@samsung.com>

-- 
Best Regards,
Samsung Electronics
Chanwoo Choi