[U-Boot] [PATCH] Exynos: uart: s5p: enabling the uart tx/rx fifo

[Simon Glass]

Hi Akshay

On Thu, Mar 21, 2013 at 11:33 PM, Akshay Saraswat <akshay.s at samsung.com>wrote:

> This patch enables the uart tx/rx fifo. Now that fifo is enabled,
> the uart read/write functions are modfied to check the UFSTAT register
> for fifo status instead of UTRSTAT (as required with fifo's enabled).
> Tested by booting linux kernel. Before enabling tx/rx fifo
> "Uncompressing linux" message is garbled and after enabling it is proper.
>

Is this because Linux enables the FIFOs?

Anyway this seems fine to me, but I have a question below.


>
> Signed-off-by: Alim Akhtar <alim.akhtar at samsung.com>
> Signed-off-by: Akshay Saraswat <akshay.s at samsung.com>
> ---
>  drivers/serial/serial_s5p.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/serial/serial_s5p.c b/drivers/serial/serial_s5p.c
> index 3c41242..e65125c 100644
> --- a/drivers/serial/serial_s5p.c
> +++ b/drivers/serial/serial_s5p.c
> @@ -30,6 +30,10 @@
>
>  DECLARE_GLOBAL_DATA_PTR;
>
> +#define RX_FIFO_COUNT_MASK     0xff
> +#define RX_FIFO_FULL_MASK      (1 << 8)
> +#define TX_FIFO_FULL_MASK      (1 << 24)
> +
>  static inline struct s5p_uart *s5p_get_base_uart(int dev_index)
>  {
>         u32 offset = dev_index * sizeof(struct s5p_uart);
> @@ -87,8 +91,8 @@ int serial_init_dev(const int dev_index)
>  {
>         struct s5p_uart *const uart = s5p_get_base_uart(dev_index);
>
> -       /* reset and enable FIFOs, set triggers to the maximum */
> -       writel(0, &uart->ufcon);
> +       /* enable FIFOs */
> +       writel(0x1, &uart->ufcon);
>

It is odd that you seem to be saying that the old code did not enable
FIFOs, but this code does? Or should you update your comment?


>         writel(0, &uart->umcon);
>         /* 8N1 */
>         writel(0x3, &uart->ulcon);
> @@ -130,7 +134,8 @@ int serial_getc_dev(const int dev_index)
>         struct s5p_uart *const uart = s5p_get_base_uart(dev_index);
>
>         /* wait for character to arrive */
> -       while (!(readl(&uart->utrstat) & 0x1)) {
> +       while (!(readl(&uart->ufstat) & (RX_FIFO_COUNT_MASK |
> +                                        RX_FIFO_FULL_MASK))) {
>                 if (serial_err_check(dev_index, 0))
>                         return 0;
>         }
> @@ -146,7 +151,7 @@ void serial_putc_dev(const char c, const int dev_index)
>         struct s5p_uart *const uart = s5p_get_base_uart(dev_index);
>
>         /* wait for room in the tx FIFO */
> -       while (!(readl(&uart->utrstat) & 0x2)) {
> +       while ((readl(&uart->ufstat) & TX_FIFO_FULL_MASK)) {
>                 if (serial_err_check(dev_index, 1))
>                         return;
>         }
> --
> 1.8.0
>
>
Regards,
Simon