The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x f8c9ad46b00453a8c075453f3745f8d263f44834 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025101627-backwash-capably-abbe@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From f8c9ad46b00453a8c075453f3745f8d263f44834 Mon Sep 17 00:00:00 2001 From: Vidya Sagar vidyas@nvidia.com Date: Mon, 22 Sep 2025 16:08:26 +0200 Subject: [PATCH] PCI: tegra194: Handle errors in BPMP response

The return value from tegra_bpmp_transfer() indicates the success or failure of the IPC transaction with BPMP. If the transaction succeeded, we also need to check the actual command's result code.

If we don't have error handling for tegra_bpmp_transfer(), we will set the pcie->ep_state to EP_STATE_ENABLED even when the tegra_bpmp_transfer() command fails. Thus, the pcie->ep_state will get out of sync with reality, and any further PERST# assert + deassert will be a no-op and will not trigger the hardware initialization sequence.

This is because pex_ep_event_pex_rst_deassert() checks the current pcie->ep_state, and does nothing if the current state is already EP_STATE_ENABLED.

Thus, it is important to have error handling for tegra_bpmp_transfer(), such that the pcie->ep_state can not get out of sync with reality, so that we will try to initialize the hardware not only during the first PERST# assert + deassert, but also during any succeeding PERST# assert + deassert.

One example where this fix is needed is when using a rock5b as host. During the initial PERST# assert + deassert (triggered by the bootloader on the rock5b) pex_ep_event_pex_rst_deassert() will get called, but for some unknown reason, the tegra_bpmp_transfer() call to initialize the PHY fails. Once Linux has been loaded on the rock5b, the PCIe driver will once again assert + deassert PERST#. However, without tegra_bpmp_transfer() error handling, this second PERST# assert + deassert will not trigger the hardware initialization sequence.

With tegra_bpmp_transfer() error handling, the second PERST# assert + deassert will once again trigger the hardware to be initialized and this time the tegra_bpmp_transfer() succeeds.

Fixes: c57247f940e8 ("PCI: tegra: Add support for PCIe endpoint mode in Tegra194") Signed-off-by: Vidya Sagar vidyas@nvidia.com [cassel: improve commit log] Signed-off-by: Niklas Cassel cassel@kernel.org Signed-off-by: Manivannan Sadhasivam mani@kernel.org Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Jon Hunter jonathanh@nvidia.com Acked-by: Thierry Reding treding@nvidia.com Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20250922140822.519796-8-cassel@kernel.org

diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c index 359d92dca86a..d71053fa4365 100644 --- a/drivers/pci/controller/dwc/pcie-tegra194.c +++ b/drivers/pci/controller/dwc/pcie-tegra194.c @@ -1214,6 +1214,7 @@ static int tegra_pcie_bpmp_set_ctrl_state(struct tegra_pcie_dw *pcie, struct mrq_uphy_response resp; struct tegra_bpmp_message msg; struct mrq_uphy_request req; + int err;

/* * Controller-5 doesn't need to have its state set by BPMP-FW in @@ -1236,7 +1237,13 @@ static int tegra_pcie_bpmp_set_ctrl_state(struct tegra_pcie_dw *pcie, msg.rx.data = &resp; msg.rx.size = sizeof(resp);

- return tegra_bpmp_transfer(pcie->bpmp, &msg); + err = tegra_bpmp_transfer(pcie->bpmp, &msg); + if (err) + return err; + if (msg.rx.ret) + return -EINVAL; + + return 0; }

static int tegra_pcie_bpmp_set_pll_state(struct tegra_pcie_dw *pcie, @@ -1245,6 +1252,7 @@ static int tegra_pcie_bpmp_set_pll_state(struct tegra_pcie_dw *pcie, struct mrq_uphy_response resp; struct tegra_bpmp_message msg; struct mrq_uphy_request req; + int err;

memset(&req, 0, sizeof(req)); memset(&resp, 0, sizeof(resp)); @@ -1264,7 +1272,13 @@ static int tegra_pcie_bpmp_set_pll_state(struct tegra_pcie_dw *pcie, msg.rx.data = &resp; msg.rx.size = sizeof(resp);

- return tegra_bpmp_transfer(pcie->bpmp, &msg); + err = tegra_bpmp_transfer(pcie->bpmp, &msg); + if (err) + return err; + if (msg.rx.ret) + return -EINVAL; + + return 0; }

static void tegra_pcie_downstream_dev_to_D0(struct tegra_pcie_dw *pcie)