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| author | Rick Altherr <raltherr@google.com> | 2017-02-14 22:09:14 -0800 |
|---|---|---|
| committer | Linus Walleij <linus.walleij@linaro.org> | 2017-03-14 14:42:22 +0100 |
| commit | c825676b0823fd43a4d08bf865f81bb188b51db1 (patch) | |
| tree | b4f2efe40ccaa2ba6c41374d8e463d437cce596a /drivers/pinctrl/aspeed | |
| parent | 3818e4a7678ea70508b6b6e72a4cbf445e1e7dfa (diff) | |
| download | linux-0-day-c825676b0823fd43a4d08bf865f81bb188b51db1.tar.gz linux-0-day-c825676b0823fd43a4d08bf865f81bb188b51db1.tar.xz | |
pinctrl: aspeed: Allow disabling Port D and Port E loopback mode
Port D and port E GPIO loopback modes are commonly enabled via hardware
straps for use with front-panel buttons. When the BMC is powered
off or fails to boot, the front-panel buttons are directly connected to
the host chipset via the loopback to allow direct power-on and reset
control. Once the BMC has booted, the loopback mode must be disabled for
the BMC to take over control of host power-on and reset.
Disabling these loopback modes requires writing to the hardware strap
register which violates the current design of assuming the system
designer chose the strap settings for a specific reason and they should
be treated as read-only. Only the two bits of the strap register related
to these loopback modes are allowed to be written and comments have been
added to explain why.
Signed-off-by: Rick Altherr <raltherr@google.com>
Acked-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Diffstat (limited to 'drivers/pinctrl/aspeed')
| -rw-r--r-- | drivers/pinctrl/aspeed/pinctrl-aspeed.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/pinctrl/aspeed/pinctrl-aspeed.c b/drivers/pinctrl/aspeed/pinctrl-aspeed.c index 76f62bd45f022..5b49952e5fad2 100644 --- a/drivers/pinctrl/aspeed/pinctrl-aspeed.c +++ b/drivers/pinctrl/aspeed/pinctrl-aspeed.c @@ -198,9 +198,19 @@ static int aspeed_sig_expr_set(const struct aspeed_sig_expr *expr, * them. This may mean that certain functions cannot be * deconfigured and is the reason we re-evaluate after writing * all descriptor bits. + * + * Port D and port E GPIO loopback modes are the only exception + * as those are commonly used with front-panel buttons to allow + * normal operation of the host when the BMC is powered off or + * fails to boot. Once the BMC has booted, the loopback mode + * must be disabled for the BMC to control host power-on and + * reset. */ - if ((desc->reg == HW_STRAP1 || desc->reg == HW_STRAP2) && - desc->ip == ASPEED_IP_SCU) + if (desc->ip == ASPEED_IP_SCU && desc->reg == HW_STRAP1 && + !(desc->mask & (BIT(21) | BIT(22)))) + continue; + + if (desc->ip == ASPEED_IP_SCU && desc->reg == HW_STRAP2) continue; ret = regmap_update_bits(maps[desc->ip], desc->reg, |