[PATCH v2] i2c: aspeed: disable additional device addresses on ast2[56]xx
From: Zev Weiss <zev@bewilderbeest.net>
Date: 2021-05-06 20:54:46
Also in:
linux-arm-kernel, linux-i2c, lkml, openbmc
Subsystem:
arm/aspeed i2c driver, i2c subsystem, i2c subsystem host drivers, the rest · Maintainers:
Ryan Chen, Wolfram Sang, Andi Shyti, Linus Torvalds
The ast25xx and ast26xx have, respectively, two and three configurable slave device addresses to the ast24xx's one. We only support using one at a time, but the others may come up in an indeterminate state depending on hardware/bootloader behavior, so we need to make sure we disable them so as to avoid ending up with phantom devices on the bus. Signed-off-by: Zev Weiss <zev@bewilderbeest.net> --- Changes since v1 [0]: - reduced to simplified approach suggested by Joel [0] https://lore.kernel.org/linux-arm-kernel/20200915184525.29665-1-zev at bewilderbeest.net/ drivers/i2c/busses/i2c-aspeed.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 724bf30600d6..67e8b97c0c95 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c@@ -727,10 +727,14 @@ static void __aspeed_i2c_reg_slave(struct aspeed_i2c_bus *bus, u16 slave_addr) { u32 addr_reg_val, func_ctrl_reg_val; - /* Set slave addr. */ - addr_reg_val = readl(bus->base + ASPEED_I2C_DEV_ADDR_REG); - addr_reg_val &= ~ASPEED_I2CD_DEV_ADDR_MASK; - addr_reg_val |= slave_addr & ASPEED_I2CD_DEV_ADDR_MASK; + /* + * Set slave addr. Reserved bits can all safely be written with zeros + * on all of ast2[456]00, so zero everything else to ensure we only + * enable a single slave address (ast2500 has two, ast2600 has three, + * the enable bits for which are also in this register) so that we don't + * end up with additional phantom devices responding on the bus. + */ + addr_reg_val = slave_addr & ASPEED_I2CD_DEV_ADDR_MASK; writel(addr_reg_val, bus->base + ASPEED_I2C_DEV_ADDR_REG); /* Turn on slave mode. */
--
2.31.1