1 files changed, 80 insertions, 0 deletions
diff --git a/debian/patches-rt/0248-tpm_tis-fix-stall-after-iowrite-s.patch b/debian/patches-rt/0248-tpm_tis-fix-stall-after-iowrite-s.patch
new file mode 100644
index 000000000..97554882b
--- /dev/null
+++ b/debian/patches-rt/0248-tpm_tis-fix-stall-after-iowrite-s.patch
@@ -0,0 +1,80 @@
+From: Haris Okanovic <haris.okanovic@ni.com>
+Date: Tue, 15 Aug 2017 15:13:08 -0500
+Subject: [PATCH 248/342] tpm_tis: fix stall after iowrite*()s
+Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=704fbd8b3a5c6a211e3b96b92a5a73ee0bba800c
+
+ioread8() operations to TPM MMIO addresses can stall the cpu when
+immediately following a sequence of iowrite*()'s to the same region.
+
+For example, cyclitest measures ~400us latency spikes when a non-RT
+usermode application communicates with an SPI-based TPM chip (Intel Atom
+E3940 system, PREEMPT_RT_FULL kernel). The spikes are caused by a
+stalling ioread8() operation following a sequence of 30+ iowrite8()s to
+the same address. I believe this happens because the write sequence is
+buffered (in cpu or somewhere along the bus), and gets flushed on the
+first LOAD instruction (ioread*()) that follows.
+
+The enclosed change appears to fix this issue: read the TPM chip's
+access register (status code) after every iowrite*() operation to
+amortize the cost of flushing data to chip across multiple instructions.
+
+Signed-off-by: Haris Okanovic <haris.okanovic@ni.com>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ drivers/char/tpm/tpm_tis.c | 29 +++++++++++++++++++++++++++--
+ 1 file changed, 27 insertions(+), 2 deletions(-)
+
+diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
+index 5a3a4f095391..5ecca6585049 100644
+--- a/drivers/char/tpm/tpm_tis.c
++++ b/drivers/char/tpm/tpm_tis.c
+@@ -54,6 +54,31 @@ static inline struct tpm_tis_tcg_phy *to_tpm_tis_tcg_phy(struct tpm_tis_data *da
+ 	return container_of(data, struct tpm_tis_tcg_phy, priv);
+ }
+ 
++#ifdef CONFIG_PREEMPT_RT_FULL
++/*
++ * Flushes previous write operations to chip so that a subsequent
++ * ioread*()s won't stall a cpu.
++ */
++static inline void tpm_tis_flush(void __iomem *iobase)
++{
++	ioread8(iobase + TPM_ACCESS(0));
++}
++#else
++#define tpm_tis_flush(iobase) do { } while (0)
++#endif
++
++static inline void tpm_tis_iowrite8(u8 b, void __iomem *iobase, u32 addr)
++{
++	iowrite8(b, iobase + addr);
++	tpm_tis_flush(iobase);
++}
++
++static inline void tpm_tis_iowrite32(u32 b, void __iomem *iobase, u32 addr)
++{
++	iowrite32(b, iobase + addr);
++	tpm_tis_flush(iobase);
++}
++
+ static int interrupts = -1;
+ module_param(interrupts, int, 0444);
+ MODULE_PARM_DESC(interrupts, "Enable interrupts");
+@@ -173,7 +198,7 @@ static int tpm_tcg_write_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
+ 	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
+ 
+ 	while (len--)
+-		iowrite8(*value++, phy->iobase + addr);
++		tpm_tis_iowrite8(*value++, phy->iobase, addr);
+ 
+ 	return 0;
+ }
+@@ -200,7 +225,7 @@ static int tpm_tcg_write32(struct tpm_tis_data *data, u32 addr, u32 value)
+ {
+ 	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
+ 
+-	iowrite32(value, phy->iobase + addr);
++	tpm_tis_iowrite32(value, phy->iobase, addr);
+ 
+ 	return 0;
+ }