PCI: keystone: Fix link training retries initiation

BugLink: https://bugs.launchpad.net/bugs/1864775

[ Upstream commit 6df19872 ]

ks_pcie_stop_link() function does not clear LTSSM_EN_VAL bit so
link training was not triggered more than once after startup.
In configurations where link can be unstable during early boot,
for example, under low temperature, it will never be established.

Fixes: 0c4ffcfe ("PCI: keystone: Add TI Keystone PCIe driver")
Signed-off-by: Yurii Monakov <monakov.y@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Andrew Murray <andrew.murray@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/pci/host/pci-keystone-dw.c

@@ -450,7 +450,7 @@ void ks_dw_pcie_initiate_link_train(struct keystone_pcie *ks_pcie)
 	/* Disable Link training */
 	val = readl(ks_pcie->va_app_base + CMD_STATUS);
 	val &= ~LTSSM_EN_VAL;
-	writel(LTSSM_EN_VAL | val,  ks_pcie->va_app_base + CMD_STATUS);
+	writel(val,  ks_pcie->va_app_base + CMD_STATUS);
 
 	/* Initiate Link Training */
 	val = readl(ks_pcie->va_app_base + CMD_STATUS);