From: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
To: "Krishna Chaitanya Chundru" <krishna.chundru@oss.qualcomm.com>,
"Manivannan Sadhasivam" <mani@kernel.org>,
"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-kernel@vger.kernel.org, mayank.rana@oss.qualcomm.com,
quic_vbadigan@quicinc.com
Subject: Re: [PATCH] PCI: qcom: Program correct T_POWER_ON value for L1.2 exit timing
Date: Tue, 4 Nov 2025 13:29:08 +0100 [thread overview]
Message-ID: <29b32098-39ca-440d-9b51-915157b752b5@oss.qualcomm.com> (raw)
In-Reply-To: <20251104-t_power_on_fux-v1-1-eb5916e47fd7@oss.qualcomm.com>
On 11/4/25 1:12 PM, Krishna Chaitanya Chundru wrote:
> The T_POWER_ON indicates the time (in μs) that a Port requires the port
> on the opposite side of Link to wait in L1.2.Exit after sampling CLKREQ#
> asserted before actively driving the interface. This value is used by
> the ASPM driver to compute the LTR_L1.2_THRESHOLD.
>
> Currently, the root port exposes a T_POWER_ON value of zero in the L1SS
> capability registers, leading to incorrect LTR_L1.2_THRESHOLD calculations.
> This can result in improper L1.2 exit behavior and can trigger AER's.
>
> To address this, program the T_POWER_ON value to 80us (scale = 1,
> value = 8) in the PCI_L1SS_CAP register during host initialization. This
> ensures that ASPM can take the root port's T_POWER_ON value into account
> while calculating the LTR_L1.2_THRESHOLD value.
Is 80us a meaningful value, or "just happens to work"?
Konrad
next prev parent reply other threads:[~2025-11-04 12:29 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-04 12:12 [PATCH] PCI: qcom: Program correct T_POWER_ON value for L1.2 exit timing Krishna Chaitanya Chundru
2025-11-04 12:29 ` Konrad Dybcio [this message]
2025-11-04 16:38 ` Krishna Chaitanya Chundru
2025-11-04 16:43 ` Konrad Dybcio
2025-11-04 16:51 ` Krishna Chaitanya Chundru
2025-11-04 17:56 ` Bjorn Helgaas
2025-11-06 5:00 ` Krishna Chaitanya Chundru
2025-11-06 6:21 ` Manivannan Sadhasivam
2025-11-06 11:42 ` Krishna Chaitanya Chundru
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