Hi Krzysztof, Bjorn,
On 18/07/2023 03:52, Vidya Sagar wrote:
After commit 4fb8e46c1bc4 ("PCI: tegra194: Enable support for 256 Byte
payload"), we set MPS=256 for tegra194 Root Ports.
By default (CONFIG_PCIE_BUS_DEFAULT set and no "pci=pcie_bus_*"
parameter), Linux configures the MPS of every device to match the
upstream bridge, which is impossible if the Root Port has MPS=256
and a device only supports MPS=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.
[ rewrote commit message based on Bjorn's suggestion ]
Fixes: 4fb8e46c1bc4 ("PCI: tegra194: Enable support for 256 Byte payload")
Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
---
V4:
* Rewrote commit message based on Bjorn's suggestion
V3:
* Fixed a build issue
V2:
* Addressed review comments from Bjorn
drivers/pci/controller/dwc/pcie-tegra194.c | 14 ++------------
1 file changed, 2 insertions(+), 12 deletions(-)
diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
index 4fdadc7b045f..a772faff14b5 100644
--- a/drivers/pci/controller/dwc/pcie-tegra194.c
+++ b/drivers/pci/controller/dwc/pcie-tegra194.c
@@ -900,11 +900,6 @@ static int tegra_pcie_dw_host_init(struct dw_pcie_rp *pp)
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);
@@ -1756,7 +1751,6 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
struct device *dev = pcie->dev;
u32 val;
int ret;
- u16 val_16;
if (pcie->ep_state == EP_STATE_ENABLED)
return;
@@ -1887,20 +1881,16 @@ static void pex_ep_event_pex_rst_deassert(struct tegra_pcie_dw *pcie)
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) {
+ u16 val_16;
+
val_16 = dw_pcie_readw_dbi(pci, pcie->pcie_cap_base +
PCI_EXP_LNKSTA);
val_16 &= ~PCI_EXP_LNKSTA_SLC;
dw_pcie_writew_dbi(pci, pcie->pcie_cap_base + PCI_EXP_LNKSTA,
val_16);
}
-
clk_set_rate(pcie->core_clk, GEN4_CORE_CLK_FREQ);
val = (ep->msi_mem_phys & MSIX_ADDR_MATCH_LOW_OFF_MASK);
I see a version of this patch here ...
https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/log/?h=controller/tegra194
However, I don't see this in -next yet. If you are happy with this
latest version, could we get this into -next?
FWIW ...
Acked-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Thanks!
Jon
--
nvpublic
