iwlwifi: cleanup/fix memory barriers
wmb(), rmb() are not needed when writel(), readl() are used as
accessors for MMIO. We use them indirectly via iowrite32(),
ioread32().
What is needed mmiowb(), for synchronizing writes coming from
different CPUs on PCIe bridge (see in patch comments). This
fortunately is not needed on x86, where mmiowb() is just
defined as compiler barrier. As iwlwifi devices are most likely
not used on anything other than x86, this is not so important
fix.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-agn.c b/drivers/net/wireless/iwlwifi/iwl-agn.c
index ce9ebeb..64bc285 100644
--- a/drivers/net/wireless/iwlwifi/iwl-agn.c
+++ b/drivers/net/wireless/iwlwifi/iwl-agn.c
@@ -334,7 +334,6 @@
/* Set starting address; reads will auto-increment */
iwl_write32(trans(priv), HBUS_TARG_MEM_RADDR, ptr);
- rmb();
/*
* Refuse to read more than would have fit into the log from
diff --git a/drivers/net/wireless/iwlwifi/iwl-io.c b/drivers/net/wireless/iwlwifi/iwl-io.c
index fa69845..081dd34 100644
--- a/drivers/net/wireless/iwlwifi/iwl-io.c
+++ b/drivers/net/wireless/iwlwifi/iwl-io.c
@@ -136,6 +136,13 @@
lockdep_assert_held(&trans->reg_lock);
__iwl_clear_bit(trans, CSR_GP_CNTRL,
CSR_GP_CNTRL_REG_FLAG_MAC_ACCESS_REQ);
+ /*
+ * Above we read the CSR_GP_CNTRL register, which will flush
+ * any previous writes, but we need the write that clears the
+ * MAC_ACCESS_REQ bit to be performed before any other writes
+ * scheduled on different CPUs (after we drop reg_lock).
+ */
+ mmiowb();
}
u32 iwl_read_direct32(struct iwl_trans *trans, u32 reg)
@@ -182,7 +189,6 @@
static inline u32 __iwl_read_prph(struct iwl_trans *trans, u32 reg)
{
iwl_write32(trans, HBUS_TARG_PRPH_RADDR, reg | (3 << 24));
- rmb();
return iwl_read32(trans, HBUS_TARG_PRPH_RDAT);
}
@@ -190,7 +196,6 @@
{
iwl_write32(trans, HBUS_TARG_PRPH_WADDR,
((addr & 0x0000FFFF) | (3 << 24)));
- wmb();
iwl_write32(trans, HBUS_TARG_PRPH_WDAT, val);
}
@@ -270,7 +275,6 @@
spin_lock_irqsave(&trans->reg_lock, flags);
if (likely(iwl_grab_nic_access(trans))) {
iwl_write32(trans, HBUS_TARG_MEM_RADDR, addr);
- rmb();
for (offs = 0; offs < words; offs++)
vals[offs] = iwl_read32(trans, HBUS_TARG_MEM_RDAT);
iwl_release_nic_access(trans);
@@ -297,8 +301,6 @@
spin_lock_irqsave(&trans->reg_lock, flags);
if (likely(iwl_grab_nic_access(trans))) {
iwl_write32(trans, HBUS_TARG_MEM_WADDR, addr);
- wmb();
-
for (offs = 0; offs < words; offs++)
iwl_write32(trans, HBUS_TARG_MEM_WDAT, vals[offs]);
iwl_release_nic_access(trans);
diff --git a/drivers/net/wireless/iwlwifi/iwl-trans-pcie-rx.c b/drivers/net/wireless/iwlwifi/iwl-trans-pcie-rx.c
index 5d1fc7b..787229b 100644
--- a/drivers/net/wireless/iwlwifi/iwl-trans-pcie-rx.c
+++ b/drivers/net/wireless/iwlwifi/iwl-trans-pcie-rx.c
@@ -750,7 +750,6 @@
/* Set starting address; reads will auto-increment */
iwl_write32(trans, HBUS_TARG_MEM_RADDR, ptr);
- rmb();
/* "time" is actually "data" for mode 0 (no timestamp).
* place event id # at far right for easier visual parsing. */