[PATCH v6 1/3] PCI: rockchip-ep: do not attempt 5.0 GT/s retraining

[Geraldo Nascimento <geraldogabriel@gmail.com>]

Drop the 5.0 GT/s Link Speed retraining code block from Rockchip PCIe
EP driver. 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

Link: https://lore.kernel.org/all/ffd05070-9879-4468-94e3-b88968b4c21b@rock-chips.com/
Cc: stable@vger.kernel.org
Reported-by: Dragan Simic <dsimic@manjaro.org>
Reported-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Geraldo Nascimento <geraldogabriel@gmail.com>
---
 drivers/pci/controller/pcie-rockchip-ep.c | 13 -------------
 1 file changed, 13 deletions(-)

diff --git a/drivers/pci/controller/pcie-rockchip-ep.c b/drivers/pci/controller/pcie-rockchip-ep.c
index 799461335762e..9ebc227a1ef84 100644
--- a/drivers/pci/controller/pcie-rockchip-ep.c
+++ b/drivers/pci/controller/pcie-rockchip-ep.c
@@ -553,19 +553,6 @@ static void rockchip_pcie_ep_link_training(struct work_struct *work)
 	if (ret)
 		goto again;
 
-	/*
-	 * Check the current speed: if gen2 speed was requested and we are not
-	 * at gen2 speed yet, retrain again for gen2.
-	 */
-	val = rockchip_pcie_read(rockchip, PCIE_CORE_CTRL);
-	if (!PCIE_LINK_IS_GEN2(val) && rockchip->link_gen == 2) {
-		/* Enable retrain for gen2 */
-		rockchip_pcie_ep_retrain_link(rockchip);
-		readl_poll_timeout(rockchip->apb_base + PCIE_CORE_CTRL,
-				   val, PCIE_LINK_IS_GEN2(val), 50,
-				   LINK_TRAIN_TIMEOUT);
-	}
-
 	/* Check again that the link is up */
 	if (!rockchip_pcie_ep_link_up(rockchip))
 		goto again;
-- 
2.54.0