Re: [PATCH 11/21] iommu/mediatek: Add power-domain operation - Pi-Hsun Shih

From: Pi-Hsun Shih <pihsun@chromium.org>
To: Yong Wu <yong.wu@mediatek.com>
Cc: "Youlin Pei (裴友林)" <youlin.pei@mediatek.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
	"Nicolas Boichat" <drinkcat@chromium.org>,
	cui.zhang@mediatek.com, srv_heupstream@mediatek.com,
	chao.hao@mediatek.com, "Robin Murphy" <robin.murphy@arm.com>,
	"open list" <linux-kernel@vger.kernel.org>,
	"Evan Green" <evgreen@chromium.org>,
	"Tomasz Figa" <tfiga@google.com>,
	iommu@lists.linux-foundation.org,
	"Rob Herring" <robh+dt@kernel.org>,
	"moderated list:ARM/Mediatek SoC support"
	<linux-mediatek@lists.infradead.org>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	ming-fan.chen@mediatek.com, anan.sun@mediatek.com,
	"Will Deacon" <will@kernel.org>,
	"moderated list:ARM/Mediatek SoC support"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 11/21] iommu/mediatek: Add power-domain operation
Date: Mon, 13 Jul 2020 15:03:31 +0800	[thread overview]
Message-ID: <CANdKZ0e3=AeCxpSHVk7daUE01L7AgJYmZ7jeOQDT169SaowL-g@mail.gmail.com> (raw)
In-Reply-To: <20200711064846.16007-12-yong.wu@mediatek.com>

On Sat, Jul 11, 2020 at 2:51 PM Yong Wu <yong.wu@mediatek.com> wrote:
>
> In the previous SoC, the M4U HW is in the EMI power domain which is
> always on. the latest M4U is in the display power domain which may be
> turned on/off, thus we have to add pm_runtime interface for it.
>
> we should enable its power before M4U hw initial. and disable it after HW
> initialize.
>
> When the engine work, the engine always enable the power and clocks for
> smi-larb/smi-common, then the M4U's power will always be powered on
> automatically via the device link with smi-common.
>
> Note: we don't enable the M4U power in iommu_map/unmap for tlb flush.
> If its power already is on, of course it is ok. if the power is off,
> the main tlb will be reset while M4U power on, thus the tlb flush while
> m4u power off is unnecessary, just skip it.
>
> Signed-off-by: Yong Wu <yong.wu@mediatek.com>
> ---
>  drivers/iommu/mtk_iommu.c | 54 ++++++++++++++++++++++++++++++++++-----
>  1 file changed, 47 insertions(+), 7 deletions(-)
> ...
>         for_each_m4u(data) {
> +               /* skip tlb flush when pm is not active */
> +               if (pm_runtime_enabled(data->dev) &&
> +                   !pm_runtime_active(data->dev))
> +                       continue;
> +

pm_runtime_active(dev) == false implies dev->power.disable_depth == 0,
which implies pm_runtime_enabled(dev) == true, so the
pm_runtime_enabled(data->dev) can be omitted here.

>                 spin_lock_irqsave(&data->tlb_lock, flags);
>                 writel_relaxed(F_INVLD_EN1 | F_INVLD_EN0,
>                                data->base + data->plat_data->inv_sel_reg);
> ...
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