From: Conor Dooley <conor@kernel.org>
To: Dharma.B@microchip.com
Cc: Conor.Dooley@microchip.com, sam@ravnborg.org,
bbrezillon@kernel.org, maarten.lankhorst@linux.intel.com,
mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com,
daniel@ffwll.ch, robh+dt@kernel.org,
krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
Nicolas.Ferre@microchip.com, alexandre.belloni@bootlin.com,
claudiu.beznea@tuxon.dev, dri-devel@lists.freedesktop.org,
devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, lee@kernel.org,
thierry.reding@gmail.com, u.kleine-koenig@pengutronix.de,
linux-pwm@vger.kernel.org, Linux4Microchip@microchip.com
Subject: Re: [PATCH v3 3/3] dt-bindings: mfd: atmel,hlcdc: Convert to DT schema format
Date: Mon, 22 Jan 2024 09:16:53 +0000 [thread overview]
Message-ID: <20240122-stark-duress-2f59294dcf27@spud> (raw)
In-Reply-To: <da60f9f3-f955-4a87-a020-5710185953c0@microchip.com>
[-- Attachment #1: Type: text/plain, Size: 6649 bytes --]
On Mon, Jan 22, 2024 at 03:38:41AM +0000, Dharma.B@microchip.com wrote:
> Hi Conor,
> On 19/01/24 5:33 pm, Conor Dooley - M52691 wrote:
> > On Fri, Jan 19, 2024 at 03:32:49AM +0000, Dharma.B@microchip.com wrote:
> >> On 18/01/24 9:10 pm, Conor Dooley wrote:
> >>> On Thu, Jan 18, 2024 at 02:56:12PM +0530, Dharma Balasubiramani wrote:
> >>>> Convert the atmel,hlcdc binding to DT schema format.
> >>>>
> >>>> Adjust the clock-names property to clarify that the LCD controller expects
> >>>> one of these clocks (either sys_clk or lvds_pll_clk to be present but not
> >>>> both) along with the slow_clk and periph_clk. This alignment with the actual
> >>>> hardware requirements will enable accurate device tree configuration for
> >>>> systems using the HLCDC IP.
> >>>>
> >>>> Signed-off-by: Dharma Balasubiramani<dharma.b@microchip.com>
> >>>> ---
> >>>> changelog
> >>>> v2 -> v3
> >>>> - Rename hlcdc-display-controller and hlcdc-pwm to generic names.
> >>>> - Modify the description by removing the unwanted comments and '|'.
> >>>> - Modify clock-names simpler.
> >>>> v1 -> v2
> >>>> - Remove the explicit copyrights.
> >>>> - Modify title (not include words like binding/driver).
> >>>> - Modify description actually describing the hardware and not the driver.
> >>>> - Add details of lvds_pll addition in commit message.
> >>>> - Ref endpoint and not endpoint-base.
> >>>> - Fix coding style.
> >>>> ...
> >>>> .../devicetree/bindings/mfd/atmel,hlcdc.yaml | 97 +++++++++++++++++++
> >>>> .../devicetree/bindings/mfd/atmel-hlcdc.txt | 56 -----------
> >>>> 2 files changed, 97 insertions(+), 56 deletions(-)
> >>>> create mode 100644 Documentation/devicetree/bindings/mfd/atmel,hlcdc.yaml
> >>>> delete mode 100644 Documentation/devicetree/bindings/mfd/atmel-hlcdc.txt
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/mfd/atmel,hlcdc.yaml b/Documentation/devicetree/bindings/mfd/atmel,hlcdc.yaml
> >>>> new file mode 100644
> >>>> index 000000000000..eccc998ac42c
> >>>> --- /dev/null
> >>>> +++ b/Documentation/devicetree/bindings/mfd/atmel,hlcdc.yaml
> >>>> @@ -0,0 +1,97 @@
> >>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> >>>> +%YAML 1.2
> >>>> +---
> >>>> +$id:http://devicetree.org/schemas/mfd/atmel,hlcdc.yaml#
> >>>> +$schema:http://devicetree.org/meta-schemas/core.yaml#
> >>>> +
> >>>> +title: Atmel's HLCD Controller
> >>>> +
> >>>> +maintainers:
> >>>> + - Nicolas Ferre<nicolas.ferre@microchip.com>
> >>>> + - Alexandre Belloni<alexandre.belloni@bootlin.com>
> >>>> + - Claudiu Beznea<claudiu.beznea@tuxon.dev>
> >>>> +
> >>>> +description:
> >>>> + The Atmel HLCDC (HLCD Controller) IP available on Atmel SoCs exposes two
> >>>> + subdevices, a PWM chip and a Display Controller.
> >>>> +
> >>>> +properties:
> >>>> + compatible:
> >>>> + enum:
> >>>> + - atmel,at91sam9n12-hlcdc
> >>>> + - atmel,at91sam9x5-hlcdc
> >>>> + - atmel,sama5d2-hlcdc
> >>>> + - atmel,sama5d3-hlcdc
> >>>> + - atmel,sama5d4-hlcdc
> >>>> + - microchip,sam9x60-hlcdc
> >>>> + - microchip,sam9x75-xlcdc
> >>>> +
> >>>> + reg:
> >>>> + maxItems: 1
> >>>> +
> >>>> + interrupts:
> >>>> + maxItems: 1
> >>>> +
> >>>> + clocks:
> >>>> + maxItems: 3
> >>> Hmm, one thing I probably should have said on the previous version, but
> >>> I missed somehow: It would be good to add an items list to the clocks
> >>> property here to explain what the 3 clocks are/are used for - especially
> >>> since there is additional complexity being added here to use either the
> >>> sys or lvds clocks.
> >> May I inquire if this approach is likely to be effective?
> >>
> >> clocks:
> >> items:
> >> - description: peripheral clock
> >> - description: generic clock or lvds pll clock
> >> Once the LVDS PLL is enabled, the pixel clock is used as the
> >> clock for LCDC, so its GCLK is no longer needed.
> >> - description: slow clock
> >> maxItems: 3
> >
> > Hmm that sounds very suspect to me. "Once the lvdspll is enabled the
> > generic clock is no longer needed" sounds like both clocks can be provided
> > to the IP on different pins and their provision is not mutually
> > exclusive, just that the IP will only actually use one at a time. If
> > that is the case, then this patch is nott correct and the binding should
> > allow for 4 clocks, with both the generic clock and the lvds pll being
> > present in the DT at the same time.
> >
> > I vaguely recall internal discussion about this problem some time back
> > but the details all escape me.
>
> Let's delve deeper into the clock configuration for LCDC_PCK.
>
> Considering the flexibility of the design, it appears that both clocks,
> sys_clk (generic clock) and lvds_pll_clk, can indeed be provided to the
> IP simultaneously. The crucial aspect, however, is that the IP will
> utilize only one of these clocks at any given time. This aligns with the
> specific requirements of the application, where the choice of clock
> depends on whether the LVDS interface or MIPI/DSI is in use.
If both clocks can physically be provided to the IP then both of them
should be in the dt. The hcldc appears to me to be a part of the SoC and
the clock routing to the IP is likely fixed.
> To ensure proper configuration of the pixel clock period, we need to
> distinctly identify which clocks are being utilized. For instance, in
> the LVDS interface scenario, the lvds_pll_clk is essential, resulting in
> LCDC_PCK being set to the source clock. Conversely, in the MIPI/DSI
> case, the LCDC GCLK is required, leading to LCDC_PCK being defined as
> source clock/CLKDIV+2.
>
> Considering the potential coexistence of sys_clk and lvds_pll_clk in the
> Device Tree (DT), we may need to introduce an additional flag in the DT.
> This flag could serve as a clear indicator of whether the LVDS interface
> or MIPI/DSI is being employed. As we discussed to drop this flag and
> just have any one of the clocks I believe that this approach provides a
> sensible and scalable solution, allowing for a comprehensive
> representation of the clocking configuration.
This is probably a question for the folks on the DRM or media side of
things, but is it not possible to determine based on the endpoint what
protocol is required?
I know that on the media side of things there's an endpoint property
that can be used to specific the bus-type - is there an equivalent
property for DRM stuff?
Cheers,
Conor.
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]
next prev parent reply other threads:[~2024-01-22 9:17 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-18 9:26 [PATCH v3 0/3] Convert Microchip's HLCDC Text based DT bindings to JSON schema Dharma Balasubiramani
2024-01-18 9:26 ` [PATCH v3 1/3] dt-bindings: display: convert Atmel's HLCDC to DT schema Dharma Balasubiramani
2024-01-18 15:31 ` Conor Dooley
2024-01-19 2:51 ` Dharma.B
2024-01-18 9:26 ` [PATCH v3 2/3] dt-bindings: atmel,hlcdc: convert pwm bindings to json-schema Dharma Balasubiramani
2024-01-18 10:16 ` Uwe Kleine-König
2024-01-20 10:03 ` Uwe Kleine-König
2024-01-19 19:45 ` Rob Herring
2024-01-24 9:58 ` Dharma.B
2024-01-18 9:26 ` [PATCH v3 3/3] dt-bindings: mfd: atmel,hlcdc: Convert to DT schema format Dharma Balasubiramani
2024-01-18 15:40 ` Conor Dooley
2024-01-19 3:32 ` Dharma.B
2024-01-19 12:03 ` Conor Dooley
2024-01-22 3:38 ` Dharma.B
2024-01-22 9:16 ` Conor Dooley [this message]
2024-01-24 5:18 ` Dharma.B
2024-01-24 16:39 ` Conor Dooley
2024-01-25 6:47 ` Dharma.B
2024-01-25 8:27 ` Conor Dooley
2024-01-26 14:22 ` Dharma.B
2024-01-26 15:33 ` Conor Dooley
2024-01-29 3:41 ` Dharma.B
2024-01-29 17:14 ` Conor Dooley
2024-01-18 19:30 ` [PATCH v3 0/3] Convert Microchip's HLCDC Text based DT bindings to JSON schema Sam Ravnborg
2024-01-19 8:41 ` Dharma.B
2024-01-19 21:33 ` Sam Ravnborg
2024-01-19 19:51 ` Rob Herring
2024-01-20 13:23 ` Sam Ravnborg
2024-01-22 3:52 ` Dharma.B
2024-01-22 16:02 ` Sam Ravnborg
2024-01-22 16:04 ` Sam Ravnborg
2024-01-24 8:55 ` Dharma.B
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240122-stark-duress-2f59294dcf27@spud \
--to=conor@kernel.org \
--cc=Conor.Dooley@microchip.com \
--cc=Dharma.B@microchip.com \
--cc=Linux4Microchip@microchip.com \
--cc=Nicolas.Ferre@microchip.com \
--cc=airlied@gmail.com \
--cc=alexandre.belloni@bootlin.com \
--cc=bbrezillon@kernel.org \
--cc=claudiu.beznea@tuxon.dev \
--cc=conor+dt@kernel.org \
--cc=daniel@ffwll.ch \
--cc=devicetree@vger.kernel.org \
--cc=dri-devel@lists.freedesktop.org \
--cc=krzysztof.kozlowski+dt@linaro.org \
--cc=lee@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pwm@vger.kernel.org \
--cc=maarten.lankhorst@linux.intel.com \
--cc=mripard@kernel.org \
--cc=robh+dt@kernel.org \
--cc=sam@ravnborg.org \
--cc=thierry.reding@gmail.com \
--cc=tzimmermann@suse.de \
--cc=u.kleine-koenig@pengutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).