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

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Date:   Tue, 20 Jul 2021 12:52:17 +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

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?

> +	return mtk_mmsys_reset_deassert(rcdev, id);
> +}
> +
> +static const struct reset_control_ops mtk_mmsys_reset_ops = {
> +	.assert = mtk_mmsys_reset_assert,
> +	.deassert = mtk_mmsys_reset_deassert,
> +	.reset = mtk_mmsys_reset,
> +};
> +
>  static int mtk_mmsys_probe(struct platform_device *pdev)
>  {
>  	struct device *dev = &pdev->dev;
> @@ -111,6 +168,18 @@ static int mtk_mmsys_probe(struct platform_device *pdev)
>  		return ret;
>  	}
>  
> +	spin_lock_init(&mmsys->lock);
> +
> +	mmsys->rcdev.owner = THIS_MODULE;
> +	mmsys->rcdev.nr_resets = 32;

Are all bits in the MMSYS_SW0_RST_B register individual reset controls?

regards
Philipp