Message-ID: <CAPVz0n0fkMYV-O4xWTBELd6HtKR83wrs+DS1wTVDOXdWuAK2OA@mail.gmail.com>
Date: Tue, 18 Nov 2025 09:16:35 +0200
From: Svyatoslav Ryhel <clamor95@...il.com>
To: Thierry Reding <thierry.reding@...il.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Jonathan Hunter <jonathanh@...dia.com>, Sowjanya Komatineni <skomatineni@...dia.com>, 
	Luca Ceresoli <luca.ceresoli@...tlin.com>, Prashant Gaikwad <pgaikwad@...dia.com>, 
	Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Mikko Perttunen <mperttunen@...dia.com>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jonas Schwöbel <jonasschwoebel@...oo.de>, 
	Dmitry Osipenko <digetx@...il.com>, Charan Pedumuru <charan.pedumuru@...il.com>, 
	Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>, Aaron Kling <webgeek1234@...il.com>, 
	Arnd Bergmann <arnd@...db.de>, dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-media@...r.kernel.org, linux-clk@...r.kernel.org, 
	linux-staging@...ts.linux.dev
Subject: Re: [PATCH v5 23/23] staging: media: tegra-video: add CSI support for
 Tegra20 and Tegra30

пн, 17 лист. 2025 р. о 13:56 Thierry Reding <thierry.reding@...il.com> пише:
>
> On Wed, Oct 22, 2025 at 05:49:30PM +0300, Svyatoslav Ryhel wrote:
> > Add support for MIPI CSI device and calibration logic found in Tegra20 and
> > Tegra30 SoC.
> >
> > To get CSI operational, an additional syncpoint was allocated to serve as
> > the CSI frame counter. Both VIP and CSI use an existing syncpoint for VI
> > frame start events. That said, the frame capture function was refactored
> > to reflect the addition of the CSI syncpoint, and the CSI-specific
> > configuration is guarded by the presence of a passed CSI channel structure
> > pointer.
> >
> > The camera capture setup's configuration was reconsidered: the first two
> > writes must be done before tegra_channel_set_stream for MIPI calibration
> > to work properly; the third write was moved to VIP/CSI-specific functions
> > since it must be source-specific; the function was placed after
> > tegra_channel_set_stream so the initial sequence is preserved and expanded.
> >
> > CSI configuration sequences were added based on downstream 3.1 kernel
> > sources and adjusted to the existing video-tegra framework. Although
> > Tegra20 and Tegra30 have the same set of configurations, they differ by
> > the number of clocks used by CSI.
> >
> > Dropped the software syncpoint counters in favor of reading syncpoints
> > directly and passing the incremented value to the polling function. If the
> > syncpoint increase fails, the PP is reset. This change should prevent
> > possible race conditions.
> >
> > MIPI calibration logic was registered in CSI since Tegra20 and Tegra30
> > have no dedicated hardware block for these operations and use CSI. These
> > calls are used for both CSI and DSI to work properly, which is why MIPI
> > calibration cannot be contained within CSI. The pads passed to the
> > calibration calls resemble CSI PORT_A (0), CSI PORT_B (1), DSI-A (3) and
> > DSI-B (4).
> >
> > Co-developed-by: Jonas Schwöbel <jonasschwoebel@...oo.de>
> > Signed-off-by: Jonas Schwöbel <jonasschwoebel@...oo.de>
> > Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> > ---
> >  drivers/staging/media/tegra-video/csi.c     |  23 +
> >  drivers/staging/media/tegra-video/csi.h     |   4 +
> >  drivers/staging/media/tegra-video/tegra20.c | 620 ++++++++++++++++++--
> >  drivers/staging/media/tegra-video/vi.h      |   2 -
> >  drivers/staging/media/tegra-video/video.c   |   6 +
> >  5 files changed, 608 insertions(+), 47 deletions(-)
>
> Sorry, didn't realize that this was supposed to be part of the earlier
> series that contains the opsification since it shows up as separate
> patch series. Admittedly the numbering should've given it away... Thanks
> Mikko for pointing that out.
>
> Anyway, most of my objections remain. You can implement this here just
> the same even without most of the extra churn in the prior patch. No
> need for moving things to a different header, just keep adding the new
> ops stuff to the existing one, which all drivers that need the
> calibration functionality already include anyway (including this). Also

So you propose to bloat host1x header with more mipi calibration stuff
just because someone placed those functions in there, instead of
creating a dedicated mipi calibration header. Even though mipi
calibration has NOTING to do with host1x, in case of Tegra114+ it is a
dedicated hw block not connected with host1x at all, and in
Tegra20/Tegra30 it is integrated part of CSI and not a direct hw block
on host1x. Having a dedicated header for mipi calibration seems more
logical then continue bloating host1x with unrelated stuff decreasing
its maintainability.

> no need to split out the SoC specific bits from the mipi.c file since,
> like I said, it's not going to grow anymore and can just remain as it
> is.
>

I proposed in that patch to separate mipi calibration framework which
is used by all Tegra SoC generations from SoC specific parts used by
Tegra114+ if form of dedicated hw block and Tegra20/Tegra30 as a part
of CSI. This enhances maintainability and improves transparency, while
you propose to squash everything into a single file making it a
maintainers hell.

> Thierry

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