firewire: ohci: add a comment on PHY reg access serialization
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 3b6f342..a818dc8 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -513,6 +513,12 @@
reg_read(ohci, OHCI1394_Version);
}
+/*
+ * Beware! read_phy_reg(), write_phy_reg(), update_phy_reg(), and
+ * read_paged_phy_reg() require the caller to hold ohci->phy_reg_mutex.
+ * In other words, only use ohci_read_phy_reg() and ohci_update_phy_reg()
+ * directly. Exceptions are intrinsically serialized contexts like pci_probe.
+ */
static int read_phy_reg(struct fw_ohci *ohci, int addr)
{
u32 val;