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([2a01:e0a:106d:1080:3de7:deff:62ea:d0f8]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a1cbedb6f7sm47064765e9.2.2026.10.16.03.24.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Oct 2026 03:24:06 -0700 (PDT) Message-ID: Date: Fri, 16 Oct 2026 12:24:05 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Reply-To: Neil Armstrong Subject: Re: [PATCH] PCI: qcom: Advertise hotplug with no command completion support To: Krishna Chaitanya Chundru , Manivannan Sadhasivam , Lorenzo Pieralisi , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , Rob Herring , Bjorn Helgaas Cc: linux-arm-msm@vger.kernel.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260314-hotplug-v1-1-96ac87d93867@oss.qualcomm.com> From: Neil Armstrong Content-Language: en-US, fr Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro In-Reply-To: <20260314-hotplug-v1-1-96ac87d93867@oss.qualcomm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi, On 3/14/26 02:56, Krishna Chaitanya Chundru wrote: > QCOM PCIe controller advertise hotplug capability in hardware but do not > support hotplug command completion. As a result, the PCI core registers > the pciehp service and issues hotplug commands that never gets completions, > leading to repeated timeout warnings and multi-second delays during boot > and suspend/resume. > > Commit a54db86ddc153 ("PCI: qcom: Do not advertise hotplug capability for > IPs v2.7.0 and v1.9.0") avoided these timeouts by clearing the Hot-Plug > Capability bit entirely, which also disabled all hotplug functionality. > > Instead of disabling hotplug, mark these controllers as not supporting > command completion by setting the No Command Completed Support (NCCS) bit > in the Slot Capabilities register. This prevents the PCI hotplug driver > from waiting for commands completion while still allowing hotplug-related > functionality such as Data Link Layer state change events. I'm a little late to the party, but marking the RC as Hotplus means the bridge is marked as is_pciehp and pci_bridge_d3_possible() returns false. This means this breaks D3Cold support completely since in __pci_host_common_d3cold_possible() we now check all PCI devices, including bridges, and the RC is not set in D3Hot anymore. The only way to enable D3Cold is to pass pcie_port_pm=force to allow D3 on all Hotplug bridges. Which may be wrong on TB bridges. Neil > > Signed-off-by: Krishna Chaitanya Chundru > --- > drivers/pci/controller/dwc/pcie-qcom.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c > index 67a16af69ddc75fca1b123e70715e692a91a9135..a2924610f3625f2456a491473c135840e31bafb9 100644 > --- a/drivers/pci/controller/dwc/pcie-qcom.c > +++ b/drivers/pci/controller/dwc/pcie-qcom.c > @@ -358,7 +358,7 @@ static void qcom_pcie_clear_hpc(struct dw_pcie *pci) > dw_pcie_dbi_ro_wr_en(pci); > > val = readl(pci->dbi_base + offset + PCI_EXP_SLTCAP); > - val &= ~PCI_EXP_SLTCAP_HPC; > + val |= PCI_EXP_SLTCAP_NCCS; > writel(val, pci->dbi_base + offset + PCI_EXP_SLTCAP); > > dw_pcie_dbi_ro_wr_dis(pci); > > --- > base-commit: 0257f64bdac7fdca30fa3cae0df8b9ecbec7733a > change-id: 20260313-hotplug-4c296595b5b8 > > Best regards,