[U-Boot] [PATCH] riscv : serial: use rx watermark to indicate rx data is present

[Sagar Kadam]

Hi Padmarao,

On Mon, Jul 15, 2019 at 5:31 PM Padmarao Begari <padmarao.b at gmail.com> wrote:
>
> Reviewed-by: Padmarao Begari <padmarao.begari at microchip.com>
> Tested-by: Padmarao Begari <padmarao.begari at microchip.com>
>

Thank you for the review and testing the changes.

> Regards
> Padmarao
>

BR,
Sagar Kadam
> On Tue, Jul 9, 2019 at 5:56 PM Sagar Shrikant Kadam <sagar.kadam at sifive.com> wrote:
>>
>> 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 at sifive.com>
>> ---
>>
>>  drivers/serial/serial_sifive.c | 23 +++++++----------------
>>  1 file changed, 7 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/serial/serial_sifive.c b/drivers/serial/serial_sifive.c
>> index fdfef69..c142ccd 100644
>> --- 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)
>> --
>> 2.7.4
>>
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