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From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: Tomasz Figa <tfiga@chromium.org>
Cc: devicetree@vger.kernel.org,
	"Eddie Cai" <eddie.cai.linux@gmail.com>,
	kernel@collabora.com, "Heiko Stübner" <heiko@sntech.de>,
	"Chen Jacob" <jacob2.chen@rock-chips.com>,
	Jeffy <jeffy.chen@rock-chips.com>, 钟以崇 <zyc@rock-chips.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Allon Huang" <allon.huang@rock-chips.com>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	"Helen Koike" <helen.koike@collabora.com>,
	"Jacob Chen" <cc@rock-chips.com>,
	"Hans Verkuil" <hans.verkuil@cisco.com>,
	"Laurent Pinchart" <laurent.pinchart@ideasonboard.com>,
	"Shunqian Zheng" <zhengsq@rock-chips.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Ezequiel Garcia" <ezequiel@collabora.com>,
	"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
	Joerg Roedel <joro@8bytes.org>,
	" <linux-arm-kernel@lists.infradead.org>,
	"Linux Media Mailing List" <linux-media@vger.kernel.org>
Subject: Re: [PATCH v8 05/14] media: rkisp1: add Rockchip ISP1 subdev driver
Date: Thu, 15 Aug 2019 13:45:15 +0300
Message-ID: <20190815104515.GO6133@paasikivi.fi.intel.com> (raw)
In-Reply-To: <CAAFQd5Cd2k5ZCDfu=a281NLOa88vpm-P7ZPWF4Nnx==iyEkn7A@mail.gmail.com>

On Thu, Aug 15, 2019 at 07:29:59PM +0900, Tomasz Figa wrote:
> On Thu, Aug 15, 2019 at 5:25 PM Sakari Ailus
> <sakari.ailus@linux.intel.com> wrote:
> >
> > Hi Helen,
> >
> > On Wed, Aug 14, 2019 at 09:58:05PM -0300, Helen Koike wrote:
> >
> > ...
> >
> > > >> +static int rkisp1_isp_sd_set_fmt(struct v4l2_subdev *sd,
> > > >> +                           struct v4l2_subdev_pad_config *cfg,
> > > >> +                           struct v4l2_subdev_format *fmt)
> > > >> +{
> > > >> +  struct rkisp1_device *isp_dev = sd_to_isp_dev(sd);
> > > >> +  struct rkisp1_isp_subdev *isp_sd = &isp_dev->isp_sdev;
> > > >> +  struct v4l2_mbus_framefmt *mf = &fmt->format;
> > > >> +
> > > >
> > > > Note that for sub-device nodes, the driver is itself responsible for
> > > > serialising the access to its data structures.
> > >
> > > But looking at subdev_do_ioctl_lock(), it seems that it serializes the
> > > ioctl calls for subdevs, no? Or I'm misunderstanding something (which is
> > > most probably) ?
> >
> > Good question. I had missed this change --- subdev_do_ioctl_lock() is
> > relatively new. But setting that lock is still not possible as the struct
> > is allocated in the framework and the device is registered before the
> > driver gets hold of it. It's a good idea to provide the same serialisation
> > for subdevs as well.
> >
> > I'll get back to this later.
> >
> > ...
> >
> > > >> +static int rkisp1_isp_sd_s_power(struct v4l2_subdev *sd, int on)
> > > >
> > > > If you support runtime PM, you shouldn't implement the s_power op.
> > >
> > > Is is ok to completly remove the usage of runtime PM then?
> > > Like this http://ix.io/1RJb ?
> >
> > Please use runtime PM instead. In the long run we should get rid of the
> > s_power op. Drivers themselves know better when the hardware they control
> > should be powered on or off.
> >
> 
> One also needs to use runtime PM to handle power domains and power
> dependencies on auxiliary devices, e.g. IOMMU.
> 
> > >
> > > tbh I'm not that familar with runtime PM and I'm not sure what is the
> > > difference of it and using s_power op (and Documentation/power/runtime_pm.rst
> > > is not being that helpful tbh).
> >
> > You can find a simple example e.g. in
> > drivers/media/platform/atmel/atmel-isi.c .
> >
> > >
> > > >
> > > > You'll still need to call s_power on external subdevs though.
> > > >
> > > >> +{
> > > >> +  struct rkisp1_device *isp_dev = sd_to_isp_dev(sd);
> > > >> +  int ret;
> > > >> +
> > > >> +  v4l2_dbg(1, rkisp1_debug, &isp_dev->v4l2_dev, "s_power: %d\n", on);
> > > >> +
> > > >> +  if (on) {
> > > >> +          ret = pm_runtime_get_sync(isp_dev->dev);
> > >
> > > If this is not ok to remove suport for runtime PM, then where should I put
> > > the call to pm_runtime_get_sync() if not in this s_power op ?
> >
> > Basically the runtime_resume and runtime_suspend callbacks are where the
> > device power state changes are implemented, and pm_runtime_get_sync and
> > pm_runtime_put are how the driver controls the power state.
> >
> > So you no longer need the s_power() op at all. The op needs to be called on
> > the pipeline however, as there are drivers that still use it.
> >
> 
> For this driver, I suppose we would _get_sync() when we start
> streaming (in the hardware, i.e. we want the ISP to start capturing
> frames) and _put() when we stop and the driver shouldn't perform any
> access to the hardware when the streaming is not active.

Agreed.

-- 
Sakari Ailus
sakari.ailus@linux.intel.com

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  reply index

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-30 18:42 [PATCH v8 00/14] Rockchip ISP1 Driver Helen Koike
2019-07-30 18:42 ` [PATCH v8 01/14] media: videodev2.h, v4l2-ioctl: add rkisp1 meta buffer format Helen Koike
2019-08-15 13:30   ` Laurent Pinchart
2019-07-30 18:42 ` [PATCH v8 02/14] media: doc: add document for " Helen Koike
2019-08-07 13:09   ` Sakari Ailus
2019-08-15 13:51   ` Laurent Pinchart
2019-07-30 18:42 ` [PATCH v8 03/14] media: rkisp1: Add user space ABI definitions Helen Koike
2019-08-15 18:46   ` Laurent Pinchart
2019-07-30 18:42 ` [PATCH v8 04/14] media: rkisp1: add Rockchip MIPI Synopsys DPHY driver Helen Koike
2019-08-07 13:05   ` Sakari Ailus
2019-08-07 13:37     ` Helen Koike
2019-08-15 17:54       ` Laurent Pinchart
2019-08-15 18:26         ` Heiko Stübner
2019-08-21 21:46         ` Helen Koike
2019-08-22  2:32           ` Laurent Pinchart
2019-07-30 18:42 ` [PATCH v8 05/14] media: rkisp1: add Rockchip ISP1 subdev driver Helen Koike
2019-08-06 18:51   ` Helen Koike
2019-08-07 10:39     ` Hans Verkuil
2019-08-15 19:35       ` Laurent Pinchart
2019-08-08  9:14   ` Sakari Ailus
2019-08-15  0:58     ` Helen Koike
2019-08-15  8:24       ` Sakari Ailus
2019-08-15 10:29         ` Tomasz Figa
2019-08-15 10:45           ` Sakari Ailus [this message]
2019-08-15 13:17         ` Sakari Ailus
2019-08-16  0:13   ` Laurent Pinchart
2019-07-30 18:42 ` [PATCH v8 06/14] media: rkisp1: add ISP1 statistics driver Helen Koike
2019-08-08  9:37   ` Sakari Ailus
2019-07-30 18:42 ` [PATCH v8 07/14] media: rkisp1: add ISP1 params driver Helen Koike
2019-07-30 18:42 ` [PATCH v8 09/14] media: rkisp1: add rockchip isp1 core driver Helen Koike
2019-08-07 15:27   ` Sakari Ailus
2019-08-08 21:59     ` Helen Koike
2019-08-09 12:05       ` Sakari Ailus
2019-08-07 15:36   ` Sakari Ailus
2019-07-30 18:42 ` [PATCH v8 10/14] dt-bindings: Document the Rockchip ISP1 bindings Helen Koike
2019-08-16  0:21   ` Laurent Pinchart
2019-07-30 18:42 ` [PATCH v8 11/14] dt-bindings: Document the Rockchip MIPI RX D-PHY bindings Helen Koike
2019-08-15 18:14   ` Laurent Pinchart
2019-07-30 18:42 ` [PATCH v8 12/14] arm64: dts: rockchip: add isp0 node for rk3399 Helen Koike
2019-07-30 18:42 ` [PATCH v8 13/14] arm64: dts: rockchip: add rx0 mipi-phy " Helen Koike
2019-07-30 18:42 ` [PATCH v8 14/14] MAINTAINERS: add entry for Rockchip ISP1 driver Helen Koike
2019-08-15 13:56   ` Laurent Pinchart
2019-07-30 20:15 ` [PATCH v8 00/14] Rockchip ISP1 Driver Hans Verkuil
2019-07-30 20:50   ` Helen Koike
2019-07-31  0:08     ` Helen Koike
2019-07-31  4:29       ` Hans Verkuil
2019-07-31  4:33         ` Hans Verkuil
2019-07-31  4:55           ` Hans Verkuil
2019-07-31 14:42             ` Helen Koike
2019-08-07 15:37 ` Sakari Ailus
2019-08-07 17:57   ` Helen Koike
2019-08-09 18:45 ` Manivannan Sadhasivam

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