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[212.182.62.129]) by smtp.gmail.com with ESMTPSA id l6-20020a2ea306000000b002cc8772c87bsm1888797lje.76.2024.01.17.01.13.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Jan 2024 01:13:20 -0800 (PST) Message-ID: Date: Wed, 17 Jan 2024 10:13:15 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 3/6] PCI: qcom: Add missing icc bandwidth vote for cpu to PCIe path Content-Language: en-US To: Johan Hovold Cc: Bryan O'Donoghue , Krishna chaitanya chundru , Bjorn Andersson , Bjorn Helgaas , Lorenzo Pieralisi , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Manivannan Sadhasivam , Rob Herring , Johan Hovold , Brian Masney , Georgi Djakov , linux-arm-msm@vger.kernel.org, vireshk@kernel.org, quic_vbadigan@quicinc.com, quic_skananth@quicinc.com, quic_nitegupt@quicinc.com, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20240112-opp_support-v6-0-77bbf7d0cc37@quicinc.com> <20240112-opp_support-v6-3-77bbf7d0cc37@quicinc.com> From: Konrad Dybcio In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 1/16/24 11:52, Johan Hovold wrote: > On Fri, Jan 12, 2024 at 11:33:15PM +0100, Konrad Dybcio wrote: >> On 12.01.2024 16:17, Bryan O'Donoghue wrote: >>> On 12/01/2024 14:22, Krishna chaitanya chundru wrote: >>>> CPU-PCIe path consits for registers PCIe BAR space, config space. >>>> As there is less access on this path compared to pcie to mem path >>>> add minimum vote i.e GEN1x1 bandwidth always. >>>> >>>> In suspend remove the cpu vote after register space access is done. >>>> >>>> Fixes: c4860af88d0c ("PCI: qcom: Add basic interconnect support") >>> >>> If this patch is a Fixes then don't you need the accompanying dts change as a parallel Fixes too ? >>> >>> i.e. without the dts update - you won't have the nodes in the dts to consume => applying this code to the stable kernel absent the dts will result in no functional change and therefore no bugfix. >> >> The Fixes tag denotes a bug fix, its use for backport autosel is just >> a nice "coincidence". >> >> Fixing a lack of a required icc path and having to rely on BL leftovers >> / keepalive bus settings is definitely worth this tag in my eyes. > > An incomplete implementation can sometimes be considered a bug, but not > always. If this is needed to enable a new use case, then it's hard to > argue that the original omission was a bug. > > And as I just mentioned to Krishna, the above Fixes tag is not correct > as that commit did not *introduce* any issue. It solved the bit that was > strictly needed for sc8280xp, but now it seems you may need something > more for an even newer platform (even if no details and motivation was > included in the commit message as it should have been). The PCIe hardware seems to be piggybacking off of others' bus bandwidth requests and I think it's just been pure luck that it didn't simply refuse to work on previous generations. So indeed, the commit message seems incomplete in explaining where the problem lies Konrad