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[104.57.184.186]) by smtp.gmail.com with ESMTPSA id y6sm620261oiy.18.2021.07.14.10.23.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Jul 2021 10:23:44 -0700 (PDT) Date: Wed, 14 Jul 2021 12:23:41 -0500 From: Bjorn Andersson To: Ulf Hansson Cc: Mark Brown , Dmitry Baryshkov , Andy Gross , Rob Herring , Liam Girdwood , Marcel Holtmann , Johan Hedberg , Luiz Augusto von Dentz , linux-arm-msm , Manivannan Sadhasivam , DTML , Linux Kernel Mailing List , linux-bluetooth@vger.kernel.org Subject: Re: [PATCH v3 2/7] regulator: qca6390: add support for QCA639x powerup sequence Message-ID: References: <20210621223141.1638189-1-dmitry.baryshkov@linaro.org> <20210621223141.1638189-3-dmitry.baryshkov@linaro.org> <20210706115517.GB4529@sirena.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-bluetooth@vger.kernel.org On Thu 08 Jul 05:09 CDT 2021, Ulf Hansson wrote: > - Peter (the email was bouncing) > > On Tue, 6 Jul 2021 at 13:55, Mark Brown wrote: > > > > On Tue, Jul 06, 2021 at 09:54:03AM +0200, Ulf Hansson wrote: > > > On Tue, 22 Jun 2021 at 00:32, Dmitry Baryshkov > > > > > > Qualcomm QCA6390/1 is a family of WiFi + Bluetooth SoCs, with BT part > > > > being controlled through the UART and WiFi being present on PCIe > > > > bus. Both blocks share common power sources. Add device driver handling > > > > power sequencing of QCA6390/1. > > > > > Power sequencing of discoverable buses have been discussed several > > > times before at LKML. The last attempt [1] I am aware of, was in 2017 > > > from Peter Chen. I don't think there is a common solution, yet. > > > > This feels a bit different to the power sequencing problem - it's not > > exposing the individual inputs to the device but rather is a block that > > manages everything but needs a bit of a kick to get things going (I'd > > guess that with ACPI it'd be triggered via AML). It's in the same space > > but it's not quite the same issue I think, something that can handle > > control of the individual resources might still struggle with this. > > Well, to me it looks very similar to those resouses we could manage > with the mmc pwrseq, for SDIO. It's also typically the same kind of > combo-chips that moved from supporting SDIO to PCIe, for improved > performance I guess. More importantly, the same constraint to > pre-power on the device is needed to allow it to be discovered/probed. > > Therefore, I think it would be worth having a common solution for > this, rather than a solution per subsystem or even worse, per device. > Representing the chip and its power needs, separate from the busses does seem reasonable. It's pretty much what Dmitry suggested originally, but his attempts to use either power-domain or regulator references to ensure ordering has been objected. Beyond this, there is a similar case (that you and I have talked about earlier) in supporting the SDX55 PCIe modem found in some devices. Where in addition to ensuring that the power rails are configured, a couple of gpios needs to be controlled and there's an incoming gpio line indicating that the firmware of the device has locked up and the power needs to be toggled and the device re-enumerated. > Unfortunately, it looks like Peter's email is bouncing so we can't get > an update from him. > And for this second part, where we need some additional logic it seems to go beyond what the power sequence discussions has touched upon so far. Regards, Bjorn