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authorZev Weiss <zev@bewilderbeest.net>2021-05-06 15:54:19 -0500
committerWolfram Sang <wsa@kernel.org>2021-05-27 21:44:19 +0200
commit3fb2e2aeafb2d28e49d9c069ac392dabe595b1ae (patch)
tree94997a1f23c1333e776fdfc5de2b3319967c16f6 /drivers/i2c
parentc8062d11e20c218b310145bc918e116423fb1e83 (diff)
i2c: aspeed: disable additional device addresses on ast2[56]xx
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> Reviewed-by: Brendan Higgins <brendanhiggins@google.com> Reviewed-by: Joel Stanley <joel@jms.id.au> Tested-by: Joel Stanley <joel@jms.id.au> Signed-off-by: Wolfram Sang <wsa@kernel.org>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-aspeed.c12
1 files 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. */