From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sudeep Holla Subject: Re: [PATCH 2/3] arm64: dts: juno: add arm,primecell-periphid override Date: Thu, 16 Jun 2016 15:42:27 +0100 Message-ID: <5762BAD3.6050405@arm.com> References: <1465228765-14038-1-git-send-email-sudeep.holla@arm.com> <1465228765-14038-3-git-send-email-sudeep.holla@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1465228765-14038-3-git-send-email-sudeep.holla-5wv7dgnIgG8@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Cc: Sudeep Holla , Jon Medhurst , Mathieu Poirier , Suzuki K Poulose , Liviu Dudau , Lorenzo Pieralisi , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org On 06/06/16 16:59, Sudeep Holla wrote: > The Linux AMBA framework probes the peripheral ids when adding the amba > devices very early on the boot. Generally they are on APB bus and just > require APB clocks to be on even when most of the core logic of the IP > is powered down. > > However on Juno, the entire debugsys domain needs to be ON to access > those CID/PID registers and hence broken by design. Accessing those > while debugsys power domain is off will lead to the bridge stalling the > transactions instead of returning the slave error. > > Since keeping the power domain on by default affects the core power(by > preventing cores entering deeper idle states), it's not feasible > solution. Instead we can provide arm,primecell-periphid override in the > device tree that prevents accessing the device early in the boot. > OK, I recently found out that AMBA bus/infrastructure can deal with powered off domains even while adding the devices. That makes this patch redundant. I had missed it initially as I tested with !CONFIG_PM option. So I raised the issue with !CONFIG_PM option[1] and it was suggested to make platform select the same[2] as there's no simple way to deal with that. Hence I will drop this patch but will post patch to select PM from ARCH_VEXPRESS to ensure we always have it enabled to deal with this platform issue. -- Regards, Sudeep [1] http://marc.info/?l=linux-pm&m=146607608629880&w=2 [2] http://marc.info/?l=linux-pm&m=146608125731479&w=2 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html