6.4-stable review patch. If anyone has any objections, please let me know.
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From: Vidya Sagar vidyas@nvidia.com
commit ebfde1584d9f037b6309fc682c96e22dac7bcb7a upstream.
After commit 4fb8e46c1bc4 ("PCI: tegra194: Enable support for 256 Byte payload"), we initialize MPS=256 for tegra194 Root Ports before enumerating the hierarchy.
Consider an Endpoint that supports only MPS=128. In the default situation (CONFIG_PCIE_BUS_DEFAULT set and no "pci=pcie_bus_*" parameter), Linux tries to configure the MPS of every device to match the upstream bridge. If the Endpoint is directly below the Root Port, Linux can reduce the Root Port MPS to 128 to match the Endpoint. But if there's a switch in the middle, Linux doesn't reduce the Root Port MPS because other devices below the switch may already be configured with MPS larger than 128.
This scenario results in uncorrectable Malformed TLP errors if the Root Port sends TLPs with payloads larger than 128 bytes. These errors can be avoided by using the "pci=pcie_bus_safe" parameter, but it doesn't seem to be a good idea to always have this parameter even for basic functionality to work.
Revert commit 4fb8e46c1bc4 ("PCI: tegra194: Enable support for 256 Byte payload") so the Root Ports default to MPS=128, which all devices support.
If peer-to-peer DMA is not required, one can use "pci=pcie_bus_perf" to get the benefit of larger MPS settings.
[bhelgaas: commit log; kwilczynski: retain "u16 val_16" declaration at the top, add missing acked by tag] Fixes: 4fb8e46c1bc4 ("PCI: tegra194: Enable support for 256 Byte payload") Link: https://lore.kernel.org/linux-pci/20230619102604.3735001-1-vidyas@nvidia.com Signed-off-by: Vidya Sagar vidyas@nvidia.com Signed-off-by: Krzysztof Wilczyński kwilczynski@kernel.org Acked-by: Jon Hunter jonathanh@nvidia.com Cc: stable@vger.kernel.org # v6.0-rc1+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/controller/dwc/pcie-tegra194.c | 10 ---------- 1 file changed, 10 deletions(-)
--- a/drivers/pci/controller/dwc/pcie-tegra194.c +++ b/drivers/pci/controller/dwc/pcie-tegra194.c @@ -883,11 +883,6 @@ static int tegra_pcie_dw_host_init(struc pcie->pcie_cap_base = dw_pcie_find_capability(&pcie->pci, PCI_CAP_ID_EXP);
- val_16 = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL); - val_16 &= ~PCI_EXP_DEVCTL_PAYLOAD; - val_16 |= PCI_EXP_DEVCTL_PAYLOAD_256B; - dw_pcie_writew_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL, val_16); - val = dw_pcie_readl_dbi(pci, PCI_IO_BASE); val &= ~(IO_BASE_IO_DECODE | IO_BASE_IO_DECODE_BIT8); dw_pcie_writel_dbi(pci, PCI_IO_BASE, val); @@ -1876,11 +1871,6 @@ static void pex_ep_event_pex_rst_deasser pcie->pcie_cap_base = dw_pcie_find_capability(&pcie->pci, PCI_CAP_ID_EXP);
- val_16 = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL); - val_16 &= ~PCI_EXP_DEVCTL_PAYLOAD; - val_16 |= PCI_EXP_DEVCTL_PAYLOAD_256B; - dw_pcie_writew_dbi(pci, pcie->pcie_cap_base + PCI_EXP_DEVCTL, val_16); - /* Clear Slot Clock Configuration bit if SRNS configuration */ if (pcie->enable_srns) { val_16 = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base +