@@ -65,6 +65,7 @@ enum s3c24xx_port_type {
struct s3c24xx_uart_info {
char *name;
enum s3c24xx_port_type type;
+ unsigned int has_usi;
unsigned int port_type;
unsigned int fifosize;
unsigned long rx_fifomask;
@@ -1352,6 +1353,28 @@ static int apple_s5l_serial_startup(struct uart_port *port)
return ret;
}
+static void exynos_usi_init(struct uart_port *port)
+{
+ struct s3c24xx_uart_port *ourport = to_ourport(port);
+ struct s3c24xx_uart_info *info = ourport->info;
+ unsigned int val;
+
+ if (!info->has_usi)
+ return;
+
+ /* Clear the software reset of USI block (it's set at startup) */
+ val = rd_regl(port, USI_CON);
+ val &= ~USI_CON_RESET_MASK;
+ wr_regl(port, USI_CON, val);
+ udelay(1);
+
+ /* Continuously provide the clock to USI IP w/o gating (for Rx mode) */
+ val = rd_regl(port, USI_OPTION);
+ val &= ~USI_OPTION_HWACG_MASK;
+ val |= USI_OPTION_HWACG_CLKREQ_ON;
+ wr_regl(port, USI_OPTION, val);
+}
+
/* power power management control */
static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
@@ -1379,6 +1402,7 @@ static void s3c24xx_serial_pm(struct uart_port *port, unsigned int level,
if (!IS_ERR(ourport->baudclk))
clk_prepare_enable(ourport->baudclk);
+ exynos_usi_init(port);
break;
default:
dev_err(port->dev, "s3c24xx_serial: unknown pm %d\n", level);
@@ -2102,6 +2126,8 @@ static int s3c24xx_serial_init_port(struct s3c24xx_uart_port *ourport,
if (ret)
pr_warn("uart: failed to enable baudclk\n");
+ exynos_usi_init(port);
+
/* Keep all interrupts masked and cleared */
switch (ourport->info->type) {
case TYPE_S3C6400:
@@ -2750,10 +2776,11 @@ static struct s3c24xx_serial_drv_data s5pv210_serial_drv_data = {
#endif
#if defined(CONFIG_ARCH_EXYNOS)
-#define EXYNOS_COMMON_SERIAL_DRV_DATA \
+#define EXYNOS_COMMON_SERIAL_DRV_DATA_USI(_has_usi) \
.info = &(struct s3c24xx_uart_info) { \
.name = "Samsung Exynos UART", \
.type = TYPE_S3C6400, \
+ .has_usi = _has_usi, \
.port_type = PORT_S3C6400, \
.has_divslot = 1, \
.rx_fifomask = S5PV210_UFSTAT_RXMASK, \
@@ -2773,6 +2800,9 @@ static struct s3c24xx_serial_drv_data s5pv210_serial_drv_data = {
.has_fracval = 1, \
} \
+#define EXYNOS_COMMON_SERIAL_DRV_DATA \
+ EXYNOS_COMMON_SERIAL_DRV_DATA_USI(0)
+
static struct s3c24xx_serial_drv_data exynos4210_serial_drv_data = {
EXYNOS_COMMON_SERIAL_DRV_DATA,
.fifosize = { 256, 64, 16, 16 },
@@ -27,6 +27,15 @@
#define S3C2410_UERSTAT (0x14)
#define S3C2410_UFSTAT (0x18)
#define S3C2410_UMSTAT (0x1C)
+#define USI_CON (0xC4)
+#define USI_OPTION (0xC8)
+
+#define USI_CON_RESET (1<<0)
+#define USI_CON_RESET_MASK (1<<0)
+
+#define USI_OPTION_HWACG_CLKREQ_ON (1<<1)
+#define USI_OPTION_HWACG_CLKSTOP_ON (1<<2)
+#define USI_OPTION_HWACG_MASK (3<<1)
#define S3C2410_LCON_CFGMASK ((0xF<<3)|(0x3))
UART block is a part of USI (Universal Serial Interface) IP-core in Samsung SoCs since Exynos9810 (e.g. in Exynos850). USI allows one to enable one of three types of serial interface: UART, SPI or I2C. That's possible because USI shares almost all internal circuits within each protocol. USI also provides some additional registers so it's possible to configure it. One USI register called USI_OPTION has reset value of 0x0. Because of this the clock gating behavior is controlled by hardware (HWACG = Hardware Auto Clock Gating), which simply means the serial won't work after reset as is. In order to make it work, USI_OPTION[2:1] bits must be set to 0b01, so that HWACG is controlled manually (by software). Bits meaning: - CLKREQ_ON = 1: clock is continuously provided to IP - CLKSTOP_ON = 0: drive IP_CLKREQ to High (needs to be set along with CLKREQ_ON = 1) USI is not present on older chips, like s3c2410, s3c2412, s3c2440, s3c6400, s5pv210, exynos5433, exynos4210. So the new boolean field '.has_usi' was added to struct s3c24xx_uart_info. USI registers will be only actually accessed when '.has_usi' field is set to "1". This feature is needed for further serial enablement on Exynos850, but some other new Exynos chips (like Exynos9810) may benefit from this feature as well. Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org> --- Changes in v3: - Added Reviewed-by tag by Krzysztof Changes in v2: - Non-intrusive modification of USI registers - Improved comments - Rearranged USI register definitions to conform with existing style drivers/tty/serial/samsung_tty.c | 32 +++++++++++++++++++++++++++++++- include/linux/serial_s3c.h | 9 +++++++++ 2 files changed, 40 insertions(+), 1 deletion(-)