Re: [PATCH 04/18] media: hantro: add reset controller support

From: Philipp Zabel <p.zabel@pengutronix.de>
To: Adrian Ratiu <adrian.ratiu@collabora.com>,
	Ezequiel Garcia <ezequiel@collabora.com>
Cc: Fruehberger Peter <Peter.Fruehberger@de.bosch.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
	Mark Brown <broonie@kernel.org>,
	kuhanh.murugasen.krishnan@intel.com,
	Daniel Vetter <daniel@ffwll.ch>,
	kernel@collabora.com, linux-media@vger.kernel.org
Subject: Re: [PATCH 04/18] media: hantro: add reset controller support
Date: Tue, 13 Oct 2020 10:11:53 +0200	[thread overview]
Message-ID: <35ebc7a7c56c86dee523812bfb55d1bac96f4b42.camel@pengutronix.de> (raw)
In-Reply-To: <20201012205957.889185-5-adrian.ratiu@collabora.com>

Hi Adrian,

On Mon, 2020-10-12 at 23:59 +0300, Adrian Ratiu wrote:
> Some SoCs might have a reset controller which disables clocks
> by default in reset state which then drivers need to unreset
> before being able to ungate a specific clock.
> 
> In this specific case, the hantro driver needs to ensure the
> peripheral clock can be properly ungated otherwise MMIO reg
> values can't be accessed.
> 
> If the SoC has no reset controller or there is no "resets" DT
> property defined, this new code will have no effect.
> 
> Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> ---
>  drivers/staging/media/hantro/hantro.h     | 1 +
>  drivers/staging/media/hantro/hantro_drv.c | 8 ++++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/staging/media/hantro/hantro.h b/drivers/staging/media/hantro/hantro.h
> index 65f9f7ea7dcf..bb442eb1974e 100644
> --- a/drivers/staging/media/hantro/hantro.h
> +++ b/drivers/staging/media/hantro/hantro.h
> @@ -183,6 +183,7 @@ struct hantro_dev {
>  	struct platform_device *pdev;
>  	struct device *dev;
>  	struct clk_bulk_data *clocks;
> +	struct reset_control *reset;
>  	void __iomem **reg_bases;
>  	void __iomem *enc_base;
>  	void __iomem *dec_base;
> diff --git a/drivers/staging/media/hantro/hantro_drv.c b/drivers/staging/media/hantro/hantro_drv.c
> index 3cd00cc0a364..c2ea54552ce9 100644
> --- a/drivers/staging/media/hantro/hantro_drv.c
> +++ b/drivers/staging/media/hantro/hantro_drv.c
> @@ -17,6 +17,7 @@
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/slab.h>
> +#include <linux/reset.h>
>  #include <linux/videodev2.h>
>  #include <linux/workqueue.h>
>  #include <media/v4l2-event.h>
> @@ -747,6 +748,13 @@ static int hantro_probe(struct platform_device *pdev)
>  
>  	INIT_DELAYED_WORK(&vpu->watchdog_work, hantro_watchdog);
>  
> +	vpu->reset = devm_reset_control_get_optional_exclusive(&pdev->dev,
> +							       NULL);
> +	if (IS_ERR(vpu->reset))
> +		vpu->reset = NULL;

Please return the error. If the optional reset is missing from the
device tree, devm_reset_control_get_optional_exclusive() returns NULL
already.

regards
Philipp

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