diff options
| author | Bill XIE <persmule@gmail.com> | 2017-10-26 11:45:49 +0800 |
|---|---|---|
| committer | Patrick Georgi <pgeorgi@google.com> | 2017-11-07 12:26:42 +0000 |
| commit | eb4ded6925d147478fb75a4afcfb6534a2faaa5a (patch) | |
| tree | 65b7acfd596c2e8e40d0e901739dc753c27ce700 /src/ec/acpi | |
| parent | c467334620cc51daa9b976a241e43a6cafbe54a8 (diff) | |
ec/acpi: add mechanisms to clear EC output queue
EC's output could be considered as a queue, and sometimes (observed on
Thinkpad T400s during cold boot) a few (only one observed) garbage bytes
may detained in such queue after power up. Those garbage bytes should be
checked and discarded first before real interactions, otherwise they may
disrupt the interaction during EC's enablement, causing a locked rfkill.
Change-Id: Iee031306c02f5211a4512c6b4ec90f7f0db196ae
Signed-off-by: Bill XIE <persmule@gmail.com>
Reviewed-on: https://review.coreboot.org/22180
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Diffstat (limited to 'src/ec/acpi')
| -rw-r--r-- | src/ec/acpi/ec.c | 15 | ||||
| -rw-r--r-- | src/ec/acpi/ec.h | 1 |
2 files changed, 16 insertions, 0 deletions
diff --git a/src/ec/acpi/ec.c b/src/ec/acpi/ec.c index a739b98df3..61cad656eb 100644 --- a/src/ec/acpi/ec.c +++ b/src/ec/acpi/ec.c @@ -111,6 +111,21 @@ u8 recv_ec_data(void) return data; } +void ec_clear_out_queue(void) +{ + int timeout = 0x7fff; + printk(BIOS_SPEW, "Clearing EC output queue...\n"); + while (--timeout && (inb(ec_cmd_reg) & EC_OBF)) { + u8 data = inb(ec_data_reg); + printk(BIOS_SPEW, "Discarding a garbage byte: 0x%02x\n", data); + udelay(10); + } + if (!timeout) + printk(BIOS_ERR, "Timeout while clearing EC output queue!\n"); + else + printk(BIOS_SPEW, "EC output queue has been cleared.\n"); +} + u8 ec_read(u8 addr) { send_ec_command(0x80); diff --git a/src/ec/acpi/ec.h b/src/ec/acpi/ec.h index d9487e9015..48982d315e 100644 --- a/src/ec/acpi/ec.h +++ b/src/ec/acpi/ec.h @@ -40,6 +40,7 @@ int send_ec_command(u8 command); int send_ec_data(u8 data); int send_ec_data_nowait(u8 data); u8 recv_ec_data(void); +void ec_clear_out_queue(void); u8 ec_status(void); u8 ec_query(void); u8 ec_read(u8 addr); |