From mboxrd@z Thu Jan 1 00:00:00 1970 From: sudeep.holla@arm.com (Sudeep Holla) Date: Fri, 17 Jun 2016 14:38:32 +0100 Subject: [PATCH] arm64: Kconfig: select PM for ARCH_VEXPRESS In-Reply-To: <4148732.Pd5phtR9Qh@wuerfel> References: <1466090128-24425-1-git-send-email-sudeep.holla@arm.com> <4148732.Pd5phtR9Qh@wuerfel> Message-ID: <5763FD58.3090300@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 17/06/16 12:53, Arnd Bergmann wrote: > On Thursday, June 16, 2016 4:15:28 PM CEST Sudeep Holla wrote: >> The Linux AMBA bus 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 >> even the coresight components' 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. >> >> Further, the AMBA framework can't deal with !CONFIG_PM case: it ignores >> the error and proceeds to access the device region. It was suggested to >> always enable CONFIG_PM in order to handle this scenario. >> >> Suggested-by: Ulf Hansson >> Signed-off-by: Sudeep Holla >> --- >> arch/arm64/Kconfig.platforms | 1 + >> 1 file changed, 1 insertion(+) >> >> Hi ARM-SoC team, >> >> The discussion on this happened on linux-pm list[1]. This is need on >> Juno once we introduce coresight components in the DT. With !CONFIG_PM, >> the board stalls on boot and hence this patch is needed. This shouldn't >> change any thing in the defconfig as couple of other platforms already >> do the same. It's needed in case all other ARCH_* configs are disabled. >> >> Without this, we need a dirty trick in the DT[2] to handle !CONFIG_PM. >> >> Can you please pick this for v4.8 ? > > Question: if AMBA cannot deal with CONFIG_PM disabled, should > the 'select' be done from CONFIG_ARM_AMBA instead? > But few platforms using AMBA may not want PM at all. > I also feel a little uncomfortable with just adding 'select PM', given > that this option is normally just implied by CONFIG_SUSPEND || > CONFIG_HIBERNATE_CALLBACKS, On that analogy, for the current requirement I would say PM_GENERIC_DOMAINS should select but it just depends on PM. > but not selected individually, I agree, but Ulf suggested this. > so we might run into regressionswhen we get configurations that > were invalid before. Sorry my build/config knowledge is limited, I don't understand what you mean by the above. I am asking just to improve my knowledge. > Then again ARCH_RENESAS seems to already do this. Yes, it was hard to find get !CONFIG_PM as many platforms select it directly or indirectly. -- Regards, Sudeep