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Wysocki" , Nicolas Saenz Julienne , Viresh Kumar , stefan.wahren@i2se.com From: Stephen Boyd Subject: Re: [PATCH v2 4/7] cpufreq: add driver for Raspbery Pi User-Agent: alot/0.8.1 Date: Thu, 06 Jun 2019 11:23:34 -0700 Message-Id: <20190606182335.1D15F20872@mail.kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190606_112335_673217_C18F362F X-CRM114-Status: GOOD ( 24.19 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: f.fainelli@gmail.com, linux-pm@vger.kernel.org, mturquette@baylibre.com, ptesarik@suse.com, linux-kernel@vger.kernel.org, mbrugger@suse.de, eric@anholt.net, bcm-kernel-feedback-list@broadcom.com, linux-rpi-kernel@lists.infradead.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org, ssuloev@orpaltech.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Quoting Nicolas Saenz Julienne (2019-06-06 11:10:04) > On Thu, 2019-06-06 at 10:36 -0700, Stephen Boyd wrote: > > Quoting Nicolas Saenz Julienne (2019-06-06 10:22:16) > > > Hi Stephen, > > > Thanks for the review. > > > > > > On Thu, 2019-06-06 at 10:09 -0700, Stephen Boyd wrote: > > > > Quoting Nicolas Saenz Julienne (2019-06-06 07:22:56) > > > > > diff --git a/drivers/cpufreq/raspberrypi-cpufreq.c > > > > > b/drivers/cpufreq/raspberrypi-cpufreq.c > > > > > new file mode 100644 > > > > > index 000000000000..99b59d5a50aa > > > > > --- /dev/null > > > > > +++ b/drivers/cpufreq/raspberrypi-cpufreq.c > > > > [...] > > > > > + > > > > > +/* > > > > > + * Since the driver depends on clk-raspberrypi, which may return > > > > > EPROBE_DEFER, > > > > > + * all the activity is performed in the probe, which may be defered as > > > > > well. > > > > > + */ > > > > > +static struct platform_driver raspberrypi_cpufreq_driver = { > > > > > + .driver = { > > > > > + .name = "raspberrypi-cpufreq", > > > > > + }, > > > > > + .probe = raspberrypi_cpufreq_probe, > > > > > + .remove = raspberrypi_cpufreq_remove, > > > > > +}; > > > > > +module_platform_driver(raspberrypi_cpufreq_driver); > > > > > > > > How does this driver probe? Do you have a node in DT named > > > > raspberrypi-cpufreq that matches and probes this? I would think this > > > > would follow the drivers/cpufreq/cpufreq-dt-platdev.c design where it's > > > > an initcall that probes the board compatible string. > > > > > > > > Or, if it depends on clk-raspberrypi probing, maybe it could create the > > > > platform device in that drivers probe function. > > > > > > Well you just reviewed that patch :) > > > > Ok. So what's your plan? > > So as discussed previously with the RPi mantainers, they preferred for the > platform device for raspberrypi-clk to be created by the firmware interface > driver. IIRC Stefan said it was more flexible and the approach used with RPi's > hwmon driver already. Also, it's not really clear whether this driver really > fits the device tree as it wouldn't be describing hardware. > > As far as raspberrypi-cpufreq is concerned the max and min frequencies are > configurable in the firmware. So we can't really integrate cpufreq into the > device tree as we need to create the opp table dynamically. Hence the dedicated > driver. On top of that the CPU might not have a clock during the init process, > as both the firmware interface and raspberrypi-clk can be compiled as modules. > So I decided the simplest solution was to create the raspberrypi-cpufreq > platform device at the end of raspberrypi-clk's probe. > > Once raspberrypi-cpufreq is loaded it queries the min/max frequencies, > populates the CPU's opp table and creates an instance of cpufreq-dt. Which > finally can operate, without the need of any dt info, as opp tables are > populated and CPUs have a clock. > > I hope this makes it a little more clear :). > Yes, thanks. I see that largely follows the commit description so it looks OK to me. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel