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Subject[PATCH 13/14] serial: tegra: report clk rate errors
Date
Standard UART controllers support +/-4% baud rate error tolerance.
Tegra186 only supports 0% to +4% error tolerance whereas other Tegra
chips support standard +/-4% rate. Add chip data for knowing error
tolerance level for each soc. Creating new compatible for Tegra194 chip
as it supports baud rate error tolerance of -2 to +2 %, different from
older chips.

Signed-off-by: Shardar Shariff Md <smohammed@nvidia.com>
Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
---
drivers/tty/serial/serial-tegra.c | 58 +++++++++++++++++++++++++++++++++++++--
1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 3c9e5c5..3e02f27 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -89,6 +89,8 @@ struct tegra_uart_chip_data {
bool fifo_mode_enable_status;
int uart_max_port;
int dma_burst_bytes;
+ int error_tolerance_low_range;
+ int error_tolerance_high_range;
};

struct tegra_baud_tolerance {
@@ -135,6 +137,8 @@ struct tegra_uart_port {
unsigned int rx_bytes_requested;
struct tegra_baud_tolerance *baud_tolerance;
int n_adjustable_baud_rates;
+ int required_rate;
+ int configured_rate;
};

static void tegra_uart_start_next_tx(struct tegra_uart_port *tup);
@@ -352,6 +356,22 @@ static long tegra_get_tolerance_rate(struct tegra_uart_port *tup,
return rate;
}

+static int tegra_check_rate_in_range(struct tegra_uart_port *tup)
+{
+ long diff;
+
+ diff = ((long)(tup->configured_rate - tup->required_rate) * 10000)
+ / tup->required_rate;
+ if (diff < (tup->cdata->error_tolerance_low_range * 100) ||
+ diff > (tup->cdata->error_tolerance_high_range * 100)) {
+ dev_err(tup->uport.dev,
+ "configured baud rate is out of range by %d", diff);
+ return -EIO;
+ }
+
+ return 0;
+}
+
static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
{
unsigned long rate;
@@ -365,6 +385,8 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)

if (tup->cdata->support_clk_src_div) {
rate = baud * 16;
+ tup->required_rate = rate;
+
if (tup->n_adjustable_baud_rates)
rate = tegra_get_tolerance_rate(tup, baud, rate);

@@ -374,7 +396,11 @@ static int tegra_set_baudrate(struct tegra_uart_port *tup, unsigned int baud)
"clk_set_rate() failed for rate %lu\n", rate);
return ret;
}
+ tup->configured_rate = clk_get_rate(tup->uart_clk);
divisor = 1;
+ ret = tegra_check_rate_in_range(tup);
+ if (ret < 0)
+ return ret;
} else {
rate = clk_get_rate(tup->uart_clk);
divisor = DIV_ROUND_CLOSEST(rate, baud * 16);
@@ -992,7 +1018,11 @@ static int tegra_uart_hw_init(struct tegra_uart_port *tup)
* enqueued
*/
tup->lcr_shadow = TEGRA_UART_DEFAULT_LSR;
- tegra_set_baudrate(tup, TEGRA_UART_DEFAULT_BAUD);
+ ret = tegra_set_baudrate(tup, TEGRA_UART_DEFAULT_BAUD);
+ if (ret < 0) {
+ dev_err(tup->uport.dev, "Failed to set baud rate\n");
+ return ret;
+ }
tup->fcr_shadow |= UART_FCR_DMA_SELECT;
tegra_uart_write(tup, tup->fcr_shadow, UART_FCR);

@@ -1191,6 +1221,7 @@ static void tegra_uart_set_termios(struct uart_port *u,
struct clk *parent_clk = clk_get_parent(tup->uart_clk);
unsigned long parent_clk_rate = clk_get_rate(parent_clk);
int max_divider = (tup->cdata->support_clk_src_div) ? 0x7FFF : 0xFFFF;
+ int ret;

max_divider *= 16;
spin_lock_irqsave(&u->lock, flags);
@@ -1263,7 +1294,11 @@ static void tegra_uart_set_termios(struct uart_port *u,
parent_clk_rate/max_divider,
parent_clk_rate/16);
spin_unlock_irqrestore(&u->lock, flags);
- tegra_set_baudrate(tup, baud);
+ ret = tegra_set_baudrate(tup, baud);
+ if (ret < 0) {
+ dev_err(tup->uport.dev, "Failed to set baud rate\n");
+ return;
+ }
if (tty_termios_baud_rate(termios))
tty_termios_encode_baud_rate(termios, baud, baud);
spin_lock_irqsave(&u->lock, flags);
@@ -1400,6 +1435,8 @@ static struct tegra_uart_chip_data tegra20_uart_chip_data = {
.fifo_mode_enable_status = false,
.uart_max_port = 5,
.dma_burst_bytes = 4,
+ .error_tolerance_low_range = 0,
+ .error_tolerance_high_range = 4,
};

static struct tegra_uart_chip_data tegra30_uart_chip_data = {
@@ -1409,6 +1446,8 @@ static struct tegra_uart_chip_data tegra30_uart_chip_data = {
.fifo_mode_enable_status = false,
.uart_max_port = 5,
.dma_burst_bytes = 4,
+ .error_tolerance_low_range = 0,
+ .error_tolerance_high_range = 4,
};

static struct tegra_uart_chip_data tegra186_uart_chip_data = {
@@ -1418,6 +1457,18 @@ static struct tegra_uart_chip_data tegra186_uart_chip_data = {
.fifo_mode_enable_status = true,
.uart_max_port = 5,
.dma_burst_bytes = 8,
+ .error_tolerance_low_range = 0,
+ .error_tolerance_high_range = 4,
+};
+
+static struct tegra_uart_chip_data tegra194_uart_chip_data = {
+ .tx_fifo_full_status = true,
+ .allow_txfifo_reset_fifo_mode = false,
+ .support_clk_src_div = true,
+ .fifo_mode_enable_status = true,
+ .dma_burst_bytes = 8,
+ .error_tolerance_low_range = -2,
+ .error_tolerance_high_range = 2,
};

static const struct of_device_id tegra_uart_of_match[] = {
@@ -1431,6 +1482,9 @@ static const struct of_device_id tegra_uart_of_match[] = {
.compatible = "nvidia,tegra186-hsuart",
.data = &tegra186_uart_chip_data,
}, {
+ .compatible = "nvidia,tegra194-hsuart",
+ .data = &tegra194_uart_chip_data,
+ }, {
},
};
MODULE_DEVICE_TABLE(of, tegra_uart_of_match);
--
2.7.4
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