riscv : serial: use rx watermark to indicate rx data is present

In y-modem transfer mode, tstc/getc fail to check if there is any
data available / received in RX FIFO, and so y-modem transfer never
succeeds. Using receive watermark bit within ip register fixes the
issue.

This patch is based on commit c7392b7bc4e1 ("Use the RX watermark
interrupt pending bit for TSTC") available at[1]

[1] https://github.com/sifive/HiFive_U-Boot/tree/regression

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam@sifive.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Tested-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Padmarao Begari <padmarao.begari@microchip.com>
Tested-by: Padmarao Begari <padmarao.begari@microchip.com>

diff --git a/drivers/serial/serial_sifive.c b/drivers/serial/serial_sifive.c
index fdfef69aaae9132a7a0a662c673c8996512890f2..c142ccdf3d57bb376496b88da95fc67570b9a1ec 100644 (file)
--- a/drivers/serial/serial_sifive.c
+++ b/drivers/serial/serial_sifive.c
@@ -22,6 +22,9 @@ DECLARE_GLOBAL_DATA_PTR;
 #define UART_TXCTRL_TXEN       0x1
 #define UART_RXCTRL_RXEN       0x1
 
+/* IP register */
+#define UART_IP_RXWM            0x2
+
 struct uart_sifive {
        u32 txfifo;
        u32 rxfifo;
@@ -34,7 +37,6 @@ struct uart_sifive {
 
 struct sifive_uart_platdata {
        unsigned long clock;
-       int saved_input_char;
        struct uart_sifive *regs;
 };
 
@@ -94,7 +96,7 @@ static int _sifive_serial_getc(struct uart_sifive *regs)
                return -EAGAIN;
        ch &= UART_RXFIFO_DATA;
 
-       return (!ch) ? -EAGAIN : ch;
+       return ch;
 }
 
 static int sifive_serial_setbrg(struct udevice *dev, int baudrate)
@@ -133,7 +135,6 @@ static int sifive_serial_probe(struct udevice *dev)
        if (gd->flags & GD_FLG_RELOC)
                return 0;
 
-       platdata->saved_input_char = 0;
        _sifive_serial_init(platdata->regs);
 
        return 0;
@@ -145,12 +146,6 @@ static int sifive_serial_getc(struct udevice *dev)
        struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
        struct uart_sifive *regs = platdata->regs;
 
-       if (platdata->saved_input_char > 0) {
-               c = platdata->saved_input_char;
-               platdata->saved_input_char = 0;
-               return c;
-       }
-
        while ((c = _sifive_serial_getc(regs)) == -EAGAIN) ;
 
        return c;
@@ -171,14 +166,10 @@ static int sifive_serial_pending(struct udevice *dev, bool input)
        struct sifive_uart_platdata *platdata = dev_get_platdata(dev);
        struct uart_sifive *regs = platdata->regs;
 
-       if (input) {
-               if (platdata->saved_input_char > 0)
-                       return 1;
-               platdata->saved_input_char = _sifive_serial_getc(regs);
-               return (platdata->saved_input_char > 0) ? 1 : 0;
-       } else {
+       if (input)
+               return (readl(&regs->ip) & UART_IP_RXWM);
+       else
                return !!(readl(&regs->txfifo) & UART_TXFIFO_FULL);
-       }
 }
 
 static int sifive_serial_ofdata_to_platdata(struct udevice *dev)