PCI: imx6: Move link up check into imx6_pcie_wait_for_link()

commit 4d107d3b5a686b5834e533a00b73bf7b1cf59df7 upstream.

imx6_pcie_link_up() previously used usleep_range() to wait for the link to
come up.  Since it may be called while holding the config spinlock, the
sleep causes a "BUG: scheduling while atomic" error.

Instead of waiting for the link to come up in imx6_pcie_link_up(), do the
waiting in imx6_pcie_wait_for_link(), where we're not holding a lock and
sleeping is allowed.

[bhelgaas: changelog, references to bugzilla and f95d3ae77191]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=100031
Fixes: f95d3ae77191 ("PCI: imx6: Wait for retraining")
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
[bwh: Backported to 3.16: also update the retry loop in
 imx6_pcie_wait_for_link() as done upstream in commit 6cbb247e85eb
 ("PCI: designware: Wait for link to come up with consistent style")]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
index d54cf5f49e1c3debc7d61c7e5a6339dcaa2b3635..c81ab705292a813be1f51ba71c627d49a1abb594 100644 (file)
--- a/drivers/pci/host/pci-imx6.c
+++ b/drivers/pci/host/pci-imx6.c
@@ -315,17 +315,33 @@ static void imx6_pcie_init_phy(struct pcie_port *pp)
 
 static int imx6_pcie_wait_for_link(struct pcie_port *pp)
 {
-       int count = 200;
+       unsigned int retries;
 
-       while (!dw_pcie_link_up(pp)) {
-               usleep_range(100, 1000);
-               if (--count)
-                       continue;
-
-               return -EINVAL;
+       /*
+        * Test if the PHY reports that the link is up and also that the LTSSM
+        * training finished. There are three possible states of the link when
+        * this code is called:
+        * 1) The link is DOWN (unlikely)
+        *    The link didn't come up yet for some reason. This usually means
+        *    we have a real problem somewhere, if it happens with a peripheral
+        *    connected. This state calls for inspection of the DEBUG registers.
+        * 2) The link is UP, but still in LTSSM training
+        *    Wait for the training to finish, which should take a very short
+        *    time. If the training does not finish, we have a problem and we
+        *    need to inspect the DEBUG registers. If the training does finish,
+        *    the link is up and operating correctly.
+        * 3) The link is UP and no longer in LTSSM training
+        *    The link is up and operating correctly.
+        */
+       for (retries = 0; retries < 200; retries++) {
+               u32 reg = readl(pp->dbi_base + PCIE_PHY_DEBUG_R1);
+               if ((reg & PCIE_PHY_DEBUG_R1_XMLH_LINK_UP) &&
+                   !(reg & PCIE_PHY_DEBUG_R1_XMLH_LINK_IN_TRAINING))
+                       return 0;
+               usleep_range(1000, 2000);
        }
 
-       return 0;
+       return -EINVAL;
 }
 
 static irqreturn_t imx6_pcie_msi_handler(int irq, void *arg)