Linux-ARM-Kernel Archive on lore.kernel.org
 help / color / Atom feed
From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Stefan Wahren <stefan.wahren@i2se.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Ray Jui <rjui@broadcom.com>,
	Scott Branden <sbranden@broadcom.com>,
	bcm-kernel-feedback-list@broadcom.com,
	Eric Anholt <eric@anholt.net>
Cc: linux-pm@vger.kernel.org, sboyd@kernel.org,
	viresh.kumar@linaro.org, mturquette@baylibre.com,
	ptesarik@suse.com, rjw@rjwysocki.net,
	linux-kernel@vger.kernel.org, mbrugger@suse.de,
	linux-rpi-kernel@lists.infradead.org, linux-clk@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, ssuloev@orpaltech.com
Subject: Re: [RFC v2 3/5] clk: bcm2835: use firmware interface to update pllb
Date: Thu, 23 May 2019 10:51:07 +0200
Message-ID: <c756c54d5e924d61b8ec6eccecf9bfdce7c2b543.camel@suse.de> (raw)
In-Reply-To: <1599901940.259900.1558475026379@email.ionos.de>

[-- Attachment #1.1: Type: text/plain, Size: 3390 bytes --]

On Tue, 2019-05-21 at 23:43 +0200, Stefan Wahren wrote:
> > Nicolas Saenz Julienne <nsaenzjulienne@suse.de> hat am 21. Mai 2019 um 17:47
> > geschrieben:
> > 
> > 
> > Hi Stefan, thanks for your comments!
> > 
> > On Tue, 2019-05-21 at 14:40 +0200, Stefan Wahren wrote:
> > > Hi Nicolas,
> > > 
> > > On 20.05.19 14:11, Stefan Wahren wrote:
> > > > Hi Nicolas,
> > > > 
> > > > the following comments applies only in case Eric is fine with the whole
> > > > approach.
> > > > 
> > > > On 20.05.19 12:47, Nicolas Saenz Julienne wrote:
> > > > > Raspberry Pi's firmware, which runs in a dedicated processor, keeps
> > > > maybe we should clarify that the firmware is running in the VPU
> > > > > track of the board's temperature and voltage. It's resposible for
> > > > > scaling the CPU frequency whenever it deems the device reached an
> > > > > unsafe
> > > > > state. On top of that the firmware provides an interface which allows
> > > > > Linux to to query the clock's state or change it's frequency.
> > > > I think this requires a separate update of the devicetree binding.
> > > > > Being the sole user of the bcm2835 clock driver, this integrates the
> > > > > firmware interface into the clock driver and adds a first user: the
> > > > > CPU
> > > > > pll, also known as 'pllb'.
> > > > Please verify that the kernel still works (and this clock driver probe)
> > > > under the following conditions:
> > > > 
> > > > - CONFIG_RASPBERRYPI_FIRMWARE=n
> > > > - CONFIG_RASPBERRYPI_FIRMWARE=m
> > > > - older DTBs without patch #1
> > > i thought about this and the case this driver would return
> > > -EPROBE_DEFER. The clock driver is too essential for doing such a thing.
> > > So i think the best solution would be to move these changes into a
> > > separate driver which should be register by the clock driver (similiar
> > > to vchiq). This also avoid the need of a new device tree binding.
> > 
> > I understand your concerns.
> > 
> > Wouldn't you prefer registering the device trough the device tree? I'd go
> > with
> > the same approach as the firmware touchscreen driver, which is registered
> > after
> > the firmware's probe trough dt's 'simple-bus'. That said, it's not a
> > strongly
> > held opinion, I'm happy with whatever solution as long as it works.
> 
> A devicetree binding always introduce some kind of inflexibility. In case
> someone finds a better solution later things can get really messy. A recent
> example is the clock handling for i2c-bcm2835.

Fair enough.

> > I get from your comments that you'd like the register based version of
> > 'pllb'
> > and 'pllb_arm' to be loaded if for some reason the firmware isn't available.
> > Is
> > that right? 
> 
> This wasn't my intention. I would prefer a simple approch here (no handover). 
> 
> > The main problem I see with this is the duplication of 'pllb' and
> > 'pllb_arm'. Both drivers will create the same clock device through different
> > interfaces. Any suggestions on how to deal with that? If not I can simply
> > remove 'pllb' and 'pllb_arm' from clk-bcm2835.c.
> 
> Yes. So even if this driver is disabled, there shouldn't be a regression. Or
> did i miss something?

No, there shoudn't be any regressions as these clocks are not being used at the
moment.

I'll send a follow-up series soon :)

Regrads,
Nicolas


[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-20 10:47 [RFC v2 0/5] cpufreq support for the Raspberry Pi Nicolas Saenz Julienne
2019-05-20 10:47 ` [RFC v2 1/5] clk: bcm2835: set CLK_GET_RATE_NOCACHE on CPU clocks Nicolas Saenz Julienne
2019-05-20 11:42   ` Stefan Wahren
2019-05-20 10:47 ` [RFC v2 2/5] clk: bcm2835: set pllb_arm divisor as readonly Nicolas Saenz Julienne
2019-05-20 11:43   ` Stefan Wahren
2019-05-20 10:47 ` [RFC v2 3/5] clk: bcm2835: use firmware interface to update pllb Nicolas Saenz Julienne
2019-05-20 12:11   ` Stefan Wahren
2019-05-20 12:14     ` Stefan Wahren
2019-05-21 12:40     ` Stefan Wahren
2019-05-21 15:47       ` Nicolas Saenz Julienne
2019-05-21 21:43         ` Stefan Wahren
2019-05-23  8:51           ` Nicolas Saenz Julienne [this message]
2019-05-20 12:43   ` Oliver Neukum
2019-05-21 11:39     ` Nicolas Saenz Julienne
2019-05-21 12:14       ` Petr Tesarik
2019-05-21 12:18         ` Nicolas Saenz Julienne
2019-05-20 10:47 ` [RFC v2 4/5] dts: bcm2837: add per-cpu clock devices Nicolas Saenz Julienne
2019-05-20 12:19   ` Stefan Wahren
2019-05-21 11:40     ` Nicolas Saenz Julienne
2019-05-20 10:47 ` [RFC v2 5/5] cpufreq: add driver for Raspbery Pi Nicolas Saenz Julienne
2019-05-20 10:51   ` Viresh Kumar
2019-05-20 12:30   ` Stefan Wahren
2019-05-20 10:51 ` [RFC v2 0/5] cpufreq support for the Raspberry Pi Viresh Kumar
2019-05-21 12:02   ` Nicolas Saenz Julienne

Reply instructions:

You may reply publically 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=c756c54d5e924d61b8ec6eccecf9bfdce7c2b543.camel@suse.de \
    --to=nsaenzjulienne@suse.de \
    --cc=bcm-kernel-feedback-list@broadcom.com \
    --cc=eric@anholt.net \
    --cc=f.fainelli@gmail.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-clk@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=linux-rpi-kernel@lists.infradead.org \
    --cc=mbrugger@suse.de \
    --cc=mturquette@baylibre.com \
    --cc=ptesarik@suse.com \
    --cc=rjui@broadcom.com \
    --cc=rjw@rjwysocki.net \
    --cc=sboyd@kernel.org \
    --cc=sbranden@broadcom.com \
    --cc=ssuloev@orpaltech.com \
    --cc=stefan.wahren@i2se.com \
    --cc=viresh.kumar@linaro.org \
    /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

Linux-ARM-Kernel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/0 linux-arm-kernel/git/0.git
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/1 linux-arm-kernel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-arm-kernel linux-arm-kernel/ https://lore.kernel.org/linux-arm-kernel \
		linux-arm-kernel@lists.infradead.org infradead-linux-arm-kernel@archiver.kernel.org
	public-inbox-index linux-arm-kernel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-arm-kernel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox