[PATCH v4 2/4] PCI: rockchip: drive at 2.5 GT/s only and error out other speeds

[Geraldo Nascimento]

Configure the core to be driven at 2.5 GT/s Link Speed and error
out on any other speed. The reason is that Shawn Lin from Rockchip
has reiterated that there may be danger of "catastrophic failure"
in using their PCIe with 5.0 GT/s speeds.

While Rockchip has done so informally without issuing a proper
errata, and the particulars are thus unknown, this may cause
data loss or worse.

This change is corroborated by RK3399 official datasheet [1], which
states maximum link speed for this platform is 2.5 GT/s.

[1] https://opensource.rock-chips.com/images/d/d7/Rockchip_RK3399_Datasheet_V2.1-20200323.pdf

Fixes: 956cd99b35a8 ("PCI: rockchip: Separate common code from RC driver")
Link: https://lore.kernel.org/all/ffd05070-9879-4468-94e3-b88968b4c21b@rock-chips.com/
Cc: stable at vger.kernel.org
Reported-by: Dragan Simic <dsimic at manjaro.org>
Reported-by: Shawn Lin <shawn.lin at rock-chips.com>
Signed-off-by: Geraldo Nascimento <geraldogabriel at gmail.com>
---
 drivers/pci/controller/pcie-rockchip.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/pcie-rockchip.c b/drivers/pci/controller/pcie-rockchip.c
index 0f88da378805..26fc350a66c1 100644
--- a/drivers/pci/controller/pcie-rockchip.c
+++ b/drivers/pci/controller/pcie-rockchip.c
@@ -66,8 +66,9 @@ int rockchip_pcie_parse_dt(struct rockchip_pcie *rockchip)
 	}
 
 	rockchip->link_gen = of_pci_get_max_link_speed(node);
-	if (rockchip->link_gen < 0 || rockchip->link_gen > 2)
-		rockchip->link_gen = 2;
+	if (rockchip->link_gen < 0 || rockchip->link_gen >= 2)
+		return dev_err_probe(dev, rockchip->link_gen,
+				     "Invalid Link Speed\n");
 
 	for (i = 0; i < ROCKCHIP_NUM_PM_RSTS; i++)
 		rockchip->pm_rsts[i].id = rockchip_pci_pm_rsts[i];
@@ -147,12 +148,8 @@ int rockchip_pcie_init_port(struct rockchip_pcie *rockchip)
 		goto err_exit_phy;
 	}
 
-	if (rockchip->link_gen == 2)
-		rockchip_pcie_write(rockchip, PCIE_CLIENT_GEN_SEL_2,
-				    PCIE_CLIENT_CONFIG);
-	else
-		rockchip_pcie_write(rockchip, PCIE_CLIENT_GEN_SEL_1,
-				    PCIE_CLIENT_CONFIG);
+	rockchip_pcie_write(rockchip, PCIE_CLIENT_GEN_SEL_1,
+			    PCIE_CLIENT_CONFIG);
 
 	regs = PCIE_CLIENT_ARI_ENABLE |
 	       PCIE_CLIENT_CONF_LANE_NUM(rockchip->lanes);
-- 
2.52.0