diff options
Diffstat (limited to 'debian/patches-rt/0282-tpm_tis-fix-stall-after-iowrite-s.patch')
| -rw-r--r-- | debian/patches-rt/0282-tpm_tis-fix-stall-after-iowrite-s.patch | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/debian/patches-rt/0282-tpm_tis-fix-stall-after-iowrite-s.patch b/debian/patches-rt/0282-tpm_tis-fix-stall-after-iowrite-s.patch new file mode 100644 index 000000000..8452ac49c --- /dev/null +++ b/debian/patches-rt/0282-tpm_tis-fix-stall-after-iowrite-s.patch @@ -0,0 +1,84 @@ +From ae8783c450876b505b7c6066ccda3b68e8d08c58 Mon Sep 17 00:00:00 2001 +From: Haris Okanovic <haris.okanovic@ni.com> +Date: Tue, 15 Aug 2017 15:13:08 -0500 +Subject: [PATCH 282/323] tpm_tis: fix stall after iowrite*()s +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz + +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 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 3e1bb28b7efd..c26ed0ce6b34 100644 +--- a/drivers/char/tpm/tpm_tis.c ++++ b/drivers/char/tpm/tpm_tis.c +@@ -50,6 +50,31 @@ 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 ++/* ++ * 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"); +@@ -186,7 +211,7 @@ 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; + } +@@ -213,7 +238,7 @@ 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; + } +-- +2.43.0 + |