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Subject[PATCH 14/14] serial: tegra: Add PIO mode support
Date
Add PIO mode support in receive and transmit path with RX interrupt
trigger of 16 bytes for Tegra194 and 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 | 117 ++++++++++++++++++++++++++++----------
1 file changed, 86 insertions(+), 31 deletions(-)

diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
index 3e02f27..6e5b418 100644
--- a/drivers/tty/serial/serial-tegra.c
+++ b/drivers/tty/serial/serial-tegra.c
@@ -139,6 +139,8 @@ struct tegra_uart_port {
int n_adjustable_baud_rates;
int required_rate;
int configured_rate;
+ bool use_rx_pio;
+ bool use_tx_pio;
};

static void tegra_uart_start_next_tx(struct tegra_uart_port *tup);
@@ -569,7 +571,7 @@ static void tegra_uart_start_next_tx(struct tegra_uart_port *tup)
if (!count)
return;

- if (count < TEGRA_UART_MIN_DMA)
+ if (tup->use_tx_pio || count < TEGRA_UART_MIN_DMA)
tegra_uart_start_pio_tx(tup, count);
else if (BYTES_TO_ALIGN(tail) > 0)
tegra_uart_start_pio_tx(tup, BYTES_TO_ALIGN(tail));
@@ -802,6 +804,18 @@ static void tegra_uart_handle_modem_signal_change(struct uart_port *u)
uart_handle_cts_change(&tup->uport, msr & UART_MSR_CTS);
}

+static void do_handle_rx_pio(struct tegra_uart_port *tup)
+{
+ struct tty_struct *tty = tty_port_tty_get(&tup->uport.state->port);
+ struct tty_port *port = &tup->uport.state->port;
+
+ tegra_uart_handle_rx_pio(tup, port);
+ if (tty) {
+ tty_flip_buffer_push(port);
+ tty_kref_put(tty);
+ }
+}
+
static irqreturn_t tegra_uart_isr(int irq, void *data)
{
struct tegra_uart_port *tup = data;
@@ -815,7 +829,7 @@ static irqreturn_t tegra_uart_isr(int irq, void *data)
while (1) {
iir = tegra_uart_read(tup, UART_IIR);
if (iir & UART_IIR_NO_INT) {
- if (is_rx_int) {
+ if (!tup->use_rx_pio && is_rx_int) {
tegra_uart_handle_rx_dma(tup);
if (tup->rx_in_progress) {
ier = tup->ier_shadow;
@@ -843,7 +857,7 @@ static irqreturn_t tegra_uart_isr(int irq, void *data)
case 4: /* End of data */
case 6: /* Rx timeout */
case 2: /* Receive */
- if (!is_rx_int) {
+ if (!tup->use_rx_pio && !is_rx_int) {
is_rx_int = true;
/* Disable Rx interrupts */
ier = tup->ier_shadow;
@@ -853,6 +867,8 @@ static irqreturn_t tegra_uart_isr(int irq, void *data)
UART_IER_RTOIE | TEGRA_UART_IER_EORD);
tup->ier_shadow = ier;
tegra_uart_write(tup, ier, UART_IER);
+ } else {
+ do_handle_rx_pio(tup);
}
break;

@@ -871,6 +887,7 @@ static irqreturn_t tegra_uart_isr(int irq, void *data)
static void tegra_uart_stop_rx(struct uart_port *u)
{
struct tegra_uart_port *tup = to_tegra_uport(u);
+ struct tty_port *port = &tup->uport.state->port;
struct dma_tx_state state;
unsigned long ier;

@@ -888,9 +905,13 @@ static void tegra_uart_stop_rx(struct uart_port *u)
tup->ier_shadow = ier;
tegra_uart_write(tup, ier, UART_IER);
tup->rx_in_progress = 0;
- dmaengine_terminate_all(tup->rx_dma_chan);
- dmaengine_tx_status(tup->rx_dma_chan, tup->rx_cookie, &state);
- tegra_uart_rx_buffer_push(tup, state.residue);
+ if (tup->rx_dma_chan && !tup->use_rx_pio) {
+ dmaengine_terminate_all(tup->rx_dma_chan);
+ dmaengine_tx_status(tup->rx_dma_chan, tup->rx_cookie, &state);
+ tegra_uart_rx_buffer_push(tup, state.residue);
+ } else {
+ tegra_uart_handle_rx_pio(tup, port);
+ }
}

static void tegra_uart_hw_deinit(struct tegra_uart_port *tup)
@@ -941,8 +962,10 @@ static void tegra_uart_hw_deinit(struct tegra_uart_port *tup)
tup->rx_in_progress = 0;
tup->tx_in_progress = 0;

- tegra_uart_dma_channel_free(tup, true);
- tegra_uart_dma_channel_free(tup, false);
+ if (!tup->use_rx_pio)
+ tegra_uart_dma_channel_free(tup, true);
+ if (!tup->use_tx_pio)
+ tegra_uart_dma_channel_free(tup, false);

clk_disable_unprepare(tup->uart_clk);
}
@@ -987,10 +1010,14 @@ static int tegra_uart_hw_init(struct tegra_uart_port *tup)
*/
tup->fcr_shadow = UART_FCR_ENABLE_FIFO;

- if (tup->cdata->dma_burst_bytes == 8)
- tup->fcr_shadow |= UART_FCR_R_TRIG_10;
- else
- tup->fcr_shadow |= UART_FCR_R_TRIG_01;
+ if (tup->use_rx_pio) {
+ tup->fcr_shadow |= UART_FCR_R_TRIG_11;
+ } else {
+ if (tup->cdata->dma_burst_bytes == 8)
+ tup->fcr_shadow |= UART_FCR_R_TRIG_10;
+ else
+ tup->fcr_shadow |= UART_FCR_R_TRIG_01;
+ }

tup->fcr_shadow |= TEGRA_UART_TX_TRIG_16B;
tegra_uart_write(tup, tup->fcr_shadow, UART_FCR);
@@ -1017,19 +1044,23 @@ static int tegra_uart_hw_init(struct tegra_uart_port *tup)
* (115200, N, 8, 1) so that the receive DMA buffer may be
* enqueued
*/
- tup->lcr_shadow = TEGRA_UART_DEFAULT_LSR;
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);
+ if (!tup->use_rx_pio) {
+ tup->lcr_shadow = TEGRA_UART_DEFAULT_LSR;
+ tup->fcr_shadow |= UART_FCR_DMA_SELECT;
+ tegra_uart_write(tup, tup->fcr_shadow, UART_FCR);

- ret = tegra_uart_start_rx_dma(tup);
- if (ret < 0) {
- dev_err(tup->uport.dev, "Not able to start Rx DMA\n");
- return ret;
+ ret = tegra_uart_start_rx_dma(tup);
+ if (ret < 0) {
+ dev_err(tup->uport.dev, "Not able to start Rx DMA\n");
+ return ret;
+ }
+ } else {
+ tegra_uart_write(tup, tup->fcr_shadow, UART_FCR);
}
tup->rx_in_progress = 1;

@@ -1051,7 +1082,12 @@ static int tegra_uart_hw_init(struct tegra_uart_port *tup)
* both the EORD as well as RX_TIMEOUT - SW sees RX_TIMEOUT first
* then the EORD.
*/
- tup->ier_shadow = UART_IER_RLSI | UART_IER_RTOIE | TEGRA_UART_IER_EORD;
+ if (!tup->use_rx_pio)
+ tup->ier_shadow = UART_IER_RLSI | UART_IER_RTOIE |
+ TEGRA_UART_IER_EORD;
+ else
+ tup->ier_shadow = UART_IER_RLSI | UART_IER_RTOIE | UART_IER_RDI;
+
tegra_uart_write(tup, tup->ier_shadow, UART_IER);
return 0;
}
@@ -1146,16 +1182,22 @@ static int tegra_uart_startup(struct uart_port *u)
struct tegra_uart_port *tup = to_tegra_uport(u);
int ret;

- ret = tegra_uart_dma_channel_allocate(tup, false);
- if (ret < 0) {
- dev_err(u->dev, "Tx Dma allocation failed, err = %d\n", ret);
- return ret;
+ if (!tup->use_tx_pio) {
+ ret = tegra_uart_dma_channel_allocate(tup, false);
+ if (ret < 0) {
+ dev_err(u->dev, "Tx Dma allocation failed, err = %d\n",
+ ret);
+ return ret;
+ }
}

- ret = tegra_uart_dma_channel_allocate(tup, true);
- if (ret < 0) {
- dev_err(u->dev, "Rx Dma allocation failed, err = %d\n", ret);
- goto fail_rx_dma;
+ if (!tup->use_rx_pio) {
+ ret = tegra_uart_dma_channel_allocate(tup, true);
+ if (ret < 0) {
+ dev_err(u->dev, "Rx Dma allocation failed, err = %d\n",
+ ret);
+ goto fail_rx_dma;
+ }
}

ret = tegra_uart_hw_init(tup);
@@ -1173,9 +1215,11 @@ static int tegra_uart_startup(struct uart_port *u)
return 0;

fail_hw_init:
- tegra_uart_dma_channel_free(tup, true);
+ if (!tup->use_rx_pio)
+ tegra_uart_dma_channel_free(tup, true);
fail_rx_dma:
- tegra_uart_dma_channel_free(tup, false);
+ if (!tup->use_tx_pio)
+ tegra_uart_dma_channel_free(tup, false);
return ret;
}

@@ -1379,7 +1423,6 @@ static int tegra_uart_parse_dt(struct platform_device *pdev,
int count;
int n_entries;

-
port = of_alias_get_id(np, "serial");
if (port < 0) {
dev_err(&pdev->dev, "failed to get alias id, errno %d\n", port);
@@ -1389,6 +1432,18 @@ static int tegra_uart_parse_dt(struct platform_device *pdev,

tup->enable_modem_interrupt = of_property_read_bool(np,
"nvidia,enable-modem-interrupt");
+
+ index = of_property_match_string(np, "dma-names", "rx");
+ if (index < 0) {
+ tup->use_rx_pio = true;
+ dev_info(&pdev->dev, "RX in PIO mode\n");
+ }
+ index = of_property_match_string(np, "dma-names", "tx");
+ if (index < 0) {
+ tup->use_tx_pio = true;
+ dev_info(&pdev->dev, "TX in PIO mode\n");
+ }
+
n_entries = of_property_count_u32_elems(np, "nvidia,adjust-baud-rates");
if (n_entries > 0) {
tup->n_adjustable_baud_rates = n_entries / 3;
--
2.7.4
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