diff options
| author | Nicolas Boichat <drinkcat@chromium.org> | 2019-06-21 19:48:34 +0800 |
|---|---|---|
| committer | Commit Bot <commit-bot@chromium.org> | 2019-06-25 14:56:07 +0000 |
| commit | f60a2d53226aeda2d8e3cabfa05457ee337ef15a (patch) | |
| tree | 55673b91ecdcb14588a183b6496870cd29973e16 /chip | |
| parent | a6b5c0b7b986aa8221c501299d1b595fc7514d21 (diff) | |
| download | chrome-ec-f60a2d53226aeda2d8e3cabfa05457ee337ef15a.tar.gz | |
chip/mt_scp/uart: Switch to use ULPOSC1_DIV10 for UART
The 26Mhz clock is not available in S3, so use ULPOSC-sourced
clock for the SCP in suspend.
Also, change ULPOSC1 frequency to 240 Mhz, as this allows for a
better division of the clock to get 115200 bps:
- 240*1000*1000/10/(115200*16.0) => 13.02 <<< lowest error
- 248*1000*1000/10/(115200*16.0) => 13.45
- 256*1000*1000/10/(115200*16.0) => 13.89
- 264*1000*1000/10/(115200*16.0) => 14.32
BRANCH=none
BUG=b:134035444
TEST=make BOARD=kukui_scp -j && \
bash board/kukui_scp/update_scp $IP
powerd_dbus_suspend
TEST=Can interract with console SCP in suspend.
TEST=Measure UART frequency with an oscilloscope: 115.7 kHz
Change-Id: I3bce4e94abaa97e20bef70f4f3ef3ca4e01d57b5
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1672646
Reviewed-by: Yilun Lin <yllin@chromium.org>
Diffstat (limited to 'chip')
| -rw-r--r-- | chip/mt_scp/clock_chip.h | 2 | ||||
| -rw-r--r-- | chip/mt_scp/registers.h | 10 | ||||
| -rw-r--r-- | chip/mt_scp/uart.c | 11 |
3 files changed, 21 insertions, 2 deletions
diff --git a/chip/mt_scp/clock_chip.h b/chip/mt_scp/clock_chip.h index 3eb02ed1ef..ab03d5c2f6 100644 --- a/chip/mt_scp/clock_chip.h +++ b/chip/mt_scp/clock_chip.h @@ -13,7 +13,7 @@ /* Default ULPOSC clock speed in MHz */ #ifndef ULPOSC1_CLOCK_MHZ -#define ULPOSC1_CLOCK_MHZ 248 +#define ULPOSC1_CLOCK_MHZ 240 #endif #ifndef ULPOSC2_CLOCK_MHZ #define ULPOSC2_CLOCK_MHZ 330 diff --git a/chip/mt_scp/registers.h b/chip/mt_scp/registers.h index a21385edf2..608efcc17b 100644 --- a/chip/mt_scp/registers.h +++ b/chip/mt_scp/registers.h @@ -327,6 +327,16 @@ #define WAKE_CKSW_SEL_SLOW_MASK 0x30 #define WAKE_CKSW_SEL_SLOW_DEFAULT 0x10 #define SCP_CLK_UART REG32(SCP_CLK_BASE + 0x44) +#define CLK_UART_SEL_MASK 0x3 +#define CLK_UART_SEL_26M 0x0 +#define CLK_UART_SEL_32K 0x1 +/* This is named ulposc_div_to_26m in datasheet */ +#define CLK_UART_SEL_ULPOSC1_DIV10 0x2 +#define CLK_UART1_SEL_MASK (0x3 << 16) +#define CLK_UART1_SEL_26M (0x0 << 16) +#define CLK_UART1_SEL_32K (0x1 << 16) +/* This is named ulposc_div_to_26m in datasheet */ +#define CLK_UART1_SEL_ULPOSC1_DIV10 (0x2 << 16) #define SCP_CLK_BCLK REG32(SCP_CLK_BASE + 0x48) #define CLK_BCLK_SEL_MASK 0x3 #define CLK_BCLK_SEL_SYS_DIV8 0x0 diff --git a/chip/mt_scp/uart.c b/chip/mt_scp/uart.c index 8717d74704..78ea594c6b 100644 --- a/chip/mt_scp/uart.c +++ b/chip/mt_scp/uart.c @@ -5,6 +5,7 @@ /* SCP UART module */ +#include "clock_chip.h" #include "console.h" #include "registers.h" #include "serial_reg.h" @@ -134,13 +135,21 @@ void uart_task(void) void uart_init(void) { const uint32_t baud_rate = CONFIG_UART_BAUD_RATE; - const uint32_t uart_clock = 26000000; + /* + * UART clock source is set to ULPOSC1 / 10 below. + * + * TODO(b:134035444): We could get slightly more precise frequency by + * using the _measured_ ULPOSC1 frequency (instead of the target). + */ + const uint32_t uart_clock = ULPOSC1_CLOCK_MHZ * 1000 / 10 * 1000; const uint32_t div = DIV_ROUND_NEAREST(uart_clock, baud_rate * 16); /* Init clock */ #if UARTN == 0 + SCP_CLK_UART = CLK_UART_SEL_ULPOSC1_DIV10; SCP_CLK_GATE |= CG_UART_M | CG_UART_B | CG_UART_RSTN; #elif UARTN == 1 + SCP_CLK_UART = CLK_UART1_SEL_ULPOSC1_DIV10; SCP_CLK_GATE |= CG_UART1_M | CG_UART1_B | CG_UART1_RSTN; #endif |