On Mon, Aug 12, 2019 at 04:58:17PM +0530, Krishna Yarlagadda wrote:
> Chips prior to Tegra186 needed delay of 3 UART clock cycles to avoid
> data loss. This issue is fixed in Tegra186 and a new flag is added to
> check if fifo mode is enabled. chip data updated to check if this flag
> is available for a chip. Tegra186 has new compatible to enable this
> flag.
>
> Signed-off-by: Shardar Shariff Md <smoham...@nvidia.com>
> Signed-off-by: Krishna Yarlagadda <kyarlaga...@nvidia.com>
> ---
> drivers/tty/serial/serial-tegra.c | 52
> ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 46 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/tty/serial/serial-tegra.c
> b/drivers/tty/serial/serial-tegra.c
> index 7ab81bb..e0379d9 100644
> --- a/drivers/tty/serial/serial-tegra.c
> +++ b/drivers/tty/serial/serial-tegra.c
> @@ -72,6 +72,8 @@
> #define TEGRA_TX_PIO 1
> #define TEGRA_TX_DMA 2
>
> +#define TEGRA_UART_FCR_IIR_FIFO_EN 0x40
> +
> /**
> * tegra_uart_chip_data: SOC specific data.
> *
> @@ -84,6 +86,7 @@ struct tegra_uart_chip_data {
> bool tx_fifo_full_status;
> bool allow_txfifo_reset_fifo_mode;
> bool support_clk_src_div;
> + bool fifo_mode_enable_status;
> };
>
> struct tegra_uart_port {
> @@ -263,6 +266,22 @@ static void tegra_uart_wait_sym_time(struct
> tegra_uart_port *tup,
> tup->current_baud));
> }
>
> +static int tegra_uart_is_fifo_mode_enabled(struct tegra_uart_port *tup)
I think this is a bad name. "is" makes it sound like this will return a
boolean value. Also, this doesn't really check whether FIFO mode is
enabled, but rather it waits for the FIFO mode to become enabled.
Perhaps, then, a better name would be
tegra_uart_wait_fifo_mode_enabled()
?
> +{
> + unsigned long iir;
> + unsigned int tmout = 100;
> +
> + do {
> + iir = tegra_uart_read(tup, UART_IIR);
> + if (iir & TEGRA_UART_FCR_IIR_FIFO_EN)
> + return 0;
> + udelay(1);
> + } while (--tmout);
> + dev_err(tup->uport.dev, "FIFO mode not enabled\n");
I'd push this out to callers. That way this function becomes useful in
situations where you don't want to output an error.
> +
> + return -EIO;
-ETIMEDOUT?
Thierry
> +}
> +
> static void tegra_uart_fifo_reset(struct tegra_uart_port *tup, u8 fcr_bits)
> {
> unsigned long fcr = tup->fcr_shadow;
> @@ -282,6 +301,8 @@ static void tegra_uart_fifo_reset(struct tegra_uart_port
> *tup, u8 fcr_bits)
> tegra_uart_write(tup, fcr, UART_FCR);
> fcr |= UART_FCR_ENABLE_FIFO;
> tegra_uart_write(tup, fcr, UART_FCR);
> + if (tup->cdata->fifo_mode_enable_status)
> + tegra_uart_is_fifo_mode_enabled(tup);
> }
>
> /* Dummy read to ensure the write is posted */
> @@ -918,12 +939,19 @@ static int tegra_uart_hw_init(struct tegra_uart_port
> *tup)
> /* Dummy read to ensure the write is posted */
> tegra_uart_read(tup, UART_SCR);
>
> - /*
> - * For all tegra devices (up to t210), there is a hardware issue that
> - * requires software to wait for 3 UART clock periods after enabling
> - * the TX fifo, otherwise data could be lost.
> - */
> - tegra_uart_wait_cycle_time(tup, 3);
> + if (tup->cdata->fifo_mode_enable_status) {
> + ret = tegra_uart_is_fifo_mode_enabled(tup);
> + if (ret < 0)
> + return ret;
> + } else {
> + /*
> + * For all tegra devices (up to t210), there is a hardware
> + * issue that requires software to wait for 3 UART clock
> + * periods after enabling the TX fifo, otherwise data could
> + * be lost.
> + */
> + tegra_uart_wait_cycle_time(tup, 3);
> + }
>
> /*
> * Initialize the UART with default configuration
> @@ -1294,12 +1322,21 @@ static struct tegra_uart_chip_data
> tegra20_uart_chip_data = {
> .tx_fifo_full_status = false,
> .allow_txfifo_reset_fifo_mode = true,
> .support_clk_src_div = false,
> + .fifo_mode_enable_status = false,
> };
>
> static struct tegra_uart_chip_data tegra30_uart_chip_data = {
> .tx_fifo_full_status = true,
> .allow_txfifo_reset_fifo_mode = false,
> .support_clk_src_div = true,
> + .fifo_mode_enable_status = false,
> +};
> +
> +static struct tegra_uart_chip_data tegra186_uart_chip_data = {
> + .tx_fifo_full_status = true,
> + .allow_txfifo_reset_fifo_mode = false,
> + .support_clk_src_div = true,
> + .fifo_mode_enable_status = true,
> };
>
> static const struct of_device_id tegra_uart_of_match[] = {
> @@ -1310,6 +1347,9 @@ static const struct of_device_id tegra_uart_of_match[]
> = {
> .compatible = "nvidia,tegra20-hsuart",
> .data = &tegra20_uart_chip_data,
> }, {
> + .compatible = "nvidia,tegra186-hsuart",
> + .data = &tegra186_uart_chip_data,
> + }, {
> },
> };
> MODULE_DEVICE_TABLE(of, tegra_uart_of_match);
> --
> 2.7.4
>
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