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Wed, 24 Jul 2024 06:31:47 -0700 (PDT) Received: from thinkpad ([103.244.168.26]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fd6f291f05sm94155675ad.90.2024.07.24.06.31.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jul 2024 06:31:47 -0700 (PDT) Date: Wed, 24 Jul 2024 19:01:39 +0530 From: Manivannan Sadhasivam To: Dmitry Baryshkov Cc: Mayank Rana , will@kernel.org, lpieralisi@kernel.org, kw@linux.com, robh@kernel.org, bhelgaas@google.com, jingoohan1@gmail.com, cassel@kernel.org, yoshihiro.shimoda.uh@renesas.com, s-vadapalli@ti.com, u.kleine-koenig@pengutronix.de, dlemoal@kernel.org, amishin@t-argos.ru, thierry.reding@gmail.com, jonathanh@nvidia.com, Frank.Li@nxp.com, ilpo.jarvinen@linux.intel.com, vidyas@nvidia.com, marek.vasut+renesas@gmail.com, krzk+dt@kernel.org, conor+dt@kernel.org, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, quic_ramkri@quicinc.com, quic_nkela@quicinc.com, quic_shazhuss@quicinc.com, quic_msarkar@quicinc.com, quic_nitegupt@quicinc.com Subject: Re: [PATCH V2 0/7] Add power domain and MSI functionality with PCIe host generic ECAM driver Message-ID: <20240724133139.GB3349@thinkpad> References: <1721067215-5832-1-git-send-email-quic_mrana@quicinc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240724_063149_242800_9C34BBD6 X-CRM114-Status: GOOD ( 22.93 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 24, 2024 at 10:12:17AM +0300, Dmitry Baryshkov wrote: > On Wed, 24 Jul 2024 at 06:58, Mayank Rana wrote: > > > > > > > > On 7/23/2024 7:13 PM, Dmitry Baryshkov wrote: > > > On Mon, Jul 15, 2024 at 11:13:28AM GMT, Mayank Rana wrote: > > >> Based on previously received feedback, this patch series adds functionalities > > >> with existing PCIe host generic ECAM driver (pci-host-generic.c) to get PCIe > > >> host root complex functionality on Qualcomm SA8775P auto platform. > > >> > > >> Previously sent RFC patchset to have separate Qualcomm PCIe ECAM platform driver: > > >> https://lore.kernel.org/all/d10199df-5fb3-407b-b404-a0a4d067341f@quicinc.com/T/ > > >> > > >> 1. Interface to allow requesting firmware to manage system resources and performing > > >> PCIe Link up (devicetree binding in terms of power domain and runtime PM APIs is used in driver) > > >> 2. Performing D3 cold with system suspend and D0 with system resume (usage of GenPD > > >> framework based power domain controls these operations) > > >> 3. SA8775P is using Synopsys Designware PCIe controller which supports MSI controller. > > >> This MSI functionality is used with PCIe host generic driver after splitting existing MSI > > >> functionality from pcie-designware-host.c file into pcie-designware-msi.c file. > > > > > > Please excuse me my ignorance if this is described somewhere. Why are > > > you using DWC-specific MSI handling instead of using GIC ITS? > > Due to usage of GIC v3 on SA8775p with Gunyah hypervisor, we have > > limitation of not supporting GIC ITS > > functionality. We considered other approach as usage of free SPIs (not > > available, limitation in terms of mismatch between number of SPIs > > available with physical GIC vs hypervisor) and extended SPIs (not > > supported with GIC hardware). Hence we just left with DWC-specific MSI > > controller here for MSI functionality. > > ... or extend Gunyah to support GIC ITS. I'd say it is a significant > deficiency if one can not use GIC ITS on Gunyah platforms. > It if were possible, Qcom would've went with that. Unfortunately, it is not. - Mani -- மணிவண்ணன் சதாசிவம்