[PATCH v23 03/16] PCI: dwc: Add missing PCI_EXP_LNKCAP_MLW handling

Yoshihiro Shimoda
2023-09-26T12:24:39Z

Update dw_pcie_link_set_max_link_width() to set PCI_EXP_LNKCAP_MLW.

In accordance with the DW PCIe RC/EP HW manuals [1,2,3,...] aside with
the PORT_LINK_CTRL_OFF.LINK_CAPABLE and GEN2_CTRL_OFF.NUM_OF_LANES[8:0]
field there is another one which needs to be updated.

It's LINK_CAPABILITIES_REG.PCIE_CAP_MAX_LINK_WIDTH. If it isn't done at
the very least the maximum link-width capability CSR won't expose the
actual maximum capability.

[1] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
Version 4.60a, March 2015, p.1032
[2] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
Version 4.70a, March 2016, p.1065
[3] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
Version 4.90a, March 2016, p.1057
...
[X] DesignWare Cores PCI Express Controller Databook - DWC PCIe Endpoint,
Version 5.40a, March 2019, p.1396
[X+1] DesignWare Cores PCI Express Controller Databook - DWC PCIe Root Port,
Version 5.40a, March 2019, p.1266

[kwilczynski: commit log]
Link: https://lore.kernel.org/linux-pci/20230825093219.2685912-8-yoshihiro.shimoda.uh@renesas.com
Suggested-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
---
drivers/pci/controller/dwc/pcie-designware.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index da4aba4aee62..2b60d20dfdf5 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -734,7 +734,8 @@ static void dw_pcie_link_set_max_speed(struct dw_pcie *pci, u32 link_gen)

static void dw_pcie_link_set_max_link_width(struct dw_pcie *pci, u32 num_lanes)
{
- u32 lwsc, plc;
+ u32 lnkcap, lwsc, plc;
+ u8 cap;

if (!num_lanes)
return;
@@ -770,6 +771,12 @@ static void dw_pcie_link_set_max_link_width(struct dw_pcie *pci, u32 num_lanes)
}
dw_pcie_writel_dbi(pci, PCIE_PORT_LINK_CONTROL, plc);
dw_pcie_writel_dbi(pci, PCIE_LINK_WIDTH_SPEED_CONTROL, lwsc);
+
+ cap = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
+ lnkcap = dw_pcie_readl_dbi(pci, cap + PCI_EXP_LNKCAP);
+ lnkcap &= ~PCI_EXP_LNKCAP_MLW;
+ lnkcap |= FIELD_PREP(PCI_EXP_LNKCAP_MLW, num_lanes);
+ dw_pcie_writel_dbi(pci, cap + PCI_EXP_LNKCAP, lnkcap);
}

void dw_pcie_iatu_detect(struct dw_pcie *pci)
--
2.25.1