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[2001:1c06:2302:5600:7555:cca3:bbc4:648b]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-64b9159ac90sm44003079a12.29.2026.01.02.08.12.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 02 Jan 2026 08:12:25 -0800 (PST) Message-ID: Date: Fri, 2 Jan 2026 16:12:21 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/7] clk: qcom: gcc: Do not turn off PCIe GDSCs during gdsc_disable() To: Konrad Dybcio , Krishna Chaitanya Chundru , Bjorn Andersson , Michael Turquette , Stephen Boyd , Taniya Das , Konrad Dybcio , Bartosz Golaszewski , Shazad Hussain , Sibi Sankar , Melody Olvera , Dmitry Baryshkov , Taniya Das , Dmitry Baryshkov , Imran Shaik , Abel Vesa Cc: linux-arm-msm@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, Rajendra Nayak , manivannan.sadhasivam@oss.qualcomm.com, stable@vger.kernel.org References: <20260102-pci_gdsc_fix-v1-0-b17ed3d175bc@oss.qualcomm.com> <500313f1-51fd-450e-877e-e4626b7652bc@oss.qualcomm.com> <4d61e8b3-0d40-4b78-9f40-a68b05284a3d@oss.qualcomm.com> Content-Language: en-US From: Bryan O'Donoghue In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 02/01/2026 13:57, Konrad Dybcio wrote: > On 1/2/26 2:19 PM, Krishna Chaitanya Chundru wrote: >> >> >> On 1/2/2026 5:09 PM, Konrad Dybcio wrote: >>> On 1/2/26 12:36 PM, Krishna Chaitanya Chundru wrote: >>>> >>>> On 1/2/2026 5:04 PM, Konrad Dybcio wrote: >>>>> On 1/2/26 10:43 AM, Krishna Chaitanya Chundru wrote: >>>>>> With PWRSTS_OFF_ON, PCIe GDSCs are turned off during gdsc_disable(). This >>>>>> can happen during scenarios such as system suspend and breaks the resume >>>>>> of PCIe controllers from suspend. >>>>> Isn't turning the GDSCs off what we want though? At least during system >>>>> suspend? >>>> If we are keeping link in D3cold it makes sense, but currently we are not keeping in D3cold >>>> so we don't expect them to get off. >>> Since we seem to be tackling that in parallel, it seems to make sense >>> that adding a mechanism to let the PCIe driver select "on" vs "ret" vs >>> "off" could be useful for us >> At least I am not aware of such API where we can tell genpd not to turn off gdsc >> at runtime if we are keeping the device in D3cold state. >> But anyway the PCIe gdsc supports Retention, in that case adding this flag here makes >> more sense as it represents HW. >> sm8450,sm8650 also had similar problem which are fixed by mani[1]. > > Perhaps I should ask for a clarification - is retention superior to > powering the GDSC off? Does it have any power costs? In retention you'd expect any/all registers to remain powered, such that configuration changes persist through your own power state. So any PLL or other clock marked as critical would require retention as would any other clock register setting you setup in probe() initially. TBH should probably have retention on all of the clocks as a default.. >>> FWIW I recall I could turn off the GDSCs on at least makena with the old >>> suspend patches and the controllers would come back to life afterwards >> In the suspend patches, we are keeping link in D3cold, so turning off gdsc will not have any effect. > > What do you mean by it won't have any effect? > >> But if some reason we skipped D3cold like in S2idle case then gdsc should not be off, in that case >> in resume PCIe link will be broken. > > Right, obviously > > Konrad