linux-kernel - Re: [PATCH v2 6/7] soc: mediatek: mmsys: Add reset controller support

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Date:   Wed, 21 Jul 2021 11:53:30 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        linux-kernel@...r.kernel.org
Cc:     chunkuang.hu@...nel.org, hsinyi@...omium.org, kernel@...labora.com,
        drinkcat@...omium.org, eizan@...omium.org,
        linux-mediatek@...ts.infradead.org, matthias.bgg@...il.com,
        jitao.shi@...iatek.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 6/7] soc: mediatek: mmsys: Add reset controller
 support

On Tue, 2021-07-20 at 19:07 +0200, Enric Balletbo i Serra wrote:
> Hi Philipp,
> 
> Thank you to take a look
> 
> On 20/7/21 12:52, Philipp Zabel wrote:
> > Hi Enric,
> > 
> > On Wed, 2021-07-14 at 12:11 +0200, Enric Balletbo i Serra wrote:
> > > Among other features the mmsys driver should implement a reset
> > > controller to be able to reset different bits from their space.
> > > 
> > > Cc: Jitao Shi <jitao.shi@...iatek.com>
> > > Suggested-by: Chun-Kuang Hu <chunkuang.hu@...nel.org>
> > > Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> > 
> > The reset controller driver looks fine, just two questions below.
> > 
> > > ---
> > > 
> > > (no changes since v1)
> > > 
> > >  drivers/soc/mediatek/mtk-mmsys.c | 69 ++++++++++++++++++++++++++++++++
> > >  drivers/soc/mediatek/mtk-mmsys.h |  2 +
> > >  2 files changed, 71 insertions(+)
> > > 
> > > diff --git a/drivers/soc/mediatek/mtk-mmsys.c b/drivers/soc/mediatek/mtk-mmsys.c
> > > index e681029fe804..6ac4deff0164 100644
> > > --- a/drivers/soc/mediatek/mtk-mmsys.c
> > > +++ b/drivers/soc/mediatek/mtk-mmsys.c
> > [...]
> > > @@ -91,6 +95,59 @@ void mtk_mmsys_ddp_disconnect(struct device *dev,
> > [...]
> > > +static int mtk_mmsys_reset(struct reset_controller_dev *rcdev, unsigned long id)
> > > +{
> > > +	int ret;
> > > +
> > > +	ret = mtk_mmsys_reset_assert(rcdev, id);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	usleep_range(1000, 1100);
> > 
> > Is this known to be enough for all IP cores that can be reset by this
> > controller?
> > 
> 
> This time is copied from the downstream kernel, so, tbh, I am not totally sure
> is enough or needed. Let me try to reach the Mediatek people for if they can
> answer this.

That would be great. When this is resolved either way, feel free to add

Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

regards
Philipp