From 83d1ba7e3da62a7860f7884a30212bd2a2bc8ab6 Mon Sep 17 00:00:00 2001 From: Julius Werner Date: Fri, 16 May 2014 11:27:46 -0700 Subject: tegra: i2c: Add a timeout to I2C bit clear recovery mechanism Our tests with the I2C bit clear mechanism (recovering from "lost arbitration" errors) show that the bit clear hardware does not work correctly in some situations. When a wedged slave device tries to send more than one 0-to-1-to-0 transition to the host (e.g. leftover bits from an aborted read), the controller never transitions the BC_ENABLE bit back to zero. This patch adds a long timeout to the bit clear code that waits for register transitions as a safeguard. This way, We will still eventually exit the function (probably followed by a reboot). Our tests show that this will recover from all conditions after at most a few reboots. BRANCH=nyan BUG=chrome-os-partner:28323 TEST=Ran wedge_ack and wedge_read tests with software_i2c patch, system recovered as expected in all cases. Original-Change-Id: I6c37119130e1240e1ef3a5944582abbcd2e39ff0 Original-Signed-off-by: Julius Werner Original-Reviewed-on: https://chromium-review.googlesource.com/200265 Original-Reviewed-by: Tom Warren Original-Reviewed-by: Gabe Black (cherry picked from commit 4c8d0af25cf107a38c856b38067b8f2f74384f22) Signed-off-by: Marc Jones Change-Id: I600d5c9a8e68719cf8795c083c5fac63f626f5bf Reviewed-on: http://review.coreboot.org/7948 Tested-by: build bot (Jenkins) Reviewed-by: David Hendricks --- src/soc/nvidia/tegra/i2c.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/src/soc/nvidia/tegra/i2c.c b/src/soc/nvidia/tegra/i2c.c index 555d0318c1..26c2559d84 100644 --- a/src/soc/nvidia/tegra/i2c.c +++ b/src/soc/nvidia/tegra/i2c.c @@ -19,6 +19,7 @@ #include #include +#include #include #include #include @@ -30,6 +31,7 @@ static void do_bus_clear(int bus) struct tegra_i2c_bus_info *info = &tegra_i2c_info[bus]; struct tegra_i2c_regs * const regs = info->base; uint32_t bc; + int i, timeout_ms = 10; // BUS CLEAR regs (from TRM): // 1. Reset the I2C controller (already done) @@ -41,16 +43,20 @@ static void do_bus_clear(int bus) write32(bc, ®s->bus_clear_config); // 4.1 Set MSTR_CONFIG_LOAD and wait for clear write32(I2C_CONFIG_LOAD_MSTR_CONFIG_LOAD_ENABLE, ®s->config_load); - do { + for (i = 0; i < timeout_ms * 10 && (read32(®s->config_load) & + I2C_CONFIG_LOAD_MSTR_CONFIG_LOAD_ENABLE); i++) { printk(BIOS_DEBUG, "%s: wait for MSTR_CONFIG_LOAD to clear\n", __func__); - } while (read32(®s->config_load) & I2C_CONFIG_LOAD_MSTR_CONFIG_LOAD_ENABLE); + udelay(100); + } // 5. Set ENABLE to start the bus clear op write32(bc | I2C_BUS_CLEAR_CONFIG_BC_ENABLE, ®s->bus_clear_config); - do { + for (i = 0; i < timeout_ms * 10 && (read32(®s->bus_clear_config) & + I2C_BUS_CLEAR_CONFIG_BC_ENABLE); i++) { printk(BIOS_DEBUG, "%s: wait for bus clear completion\n", __func__); - } while (read32(®s->bus_clear_config) & I2C_BUS_CLEAR_CONFIG_BC_ENABLE); + udelay(100); + } } static int tegra_i2c_send_recv(int bus, int read, -- cgit v1.2.3