Re: [PATCH v2 2/2] tty/serial: atmel: add ISO7816 support

From: Richard Genoud
Date: Fri Jul 27 2018 - 10:46:39 EST

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Hi Ludovic,

On 19/07/2018 10:47, Ludovic Desroches wrote:
> From: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
>
> When mode is set in atmel_config_iso7816() we backup last RS232 mode
> for coming back to this mode if requested.
> Also allow setup of T=0 and T=1 parameter and basic support in set_termios
> function as well.
> Report NACK and ITER errors in irq handler.
>
> Signed-off-by: Nicolas Ferre <nicolas.ferre@xxxxxxxxxxxxx>
> Signed-off-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxxxxxx>
> ---
> drivers/tty/serial/atmel_serial.c | 170 +++++++++++++++++++++++++++++++++++---
> drivers/tty/serial/atmel_serial.h | 3 +-
> 2 files changed, 162 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index 8e4428725848..cec958f1e7d4 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -34,6 +34,7 @@
> #include <linux/suspend.h>
> #include <linux/mm.h>
>
> +#include <asm/div64.h>
> #include <asm/io.h>
> #include <asm/ioctls.h>
>
> @@ -147,6 +148,8 @@ struct atmel_uart_port {
> struct circ_buf rx_ring;
>
> struct mctrl_gpios *gpios;
> + u32 backup_mode; /* MR saved during iso7816 operations */
> + u32 backup_brgr; /* BRGR saved during iso7816 operations */
> unsigned int tx_done_mask;
> u32 fifo_size;
> u32 rts_high;
> @@ -362,6 +365,132 @@ static int atmel_config_rs485(struct uart_port *port,
> return 0;
> }
>
> +static unsigned int atmel_calc_cd(struct uart_port *port,
> + struct serial_iso7816 *iso7816conf)
> +{
> + struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> + unsigned int cd;
> + u64 mck_rate;
> +
> + mck_rate = (u64)clk_get_rate(atmel_port->clk);
> + do_div(mck_rate, iso7816conf->clk);
> + cd = mck_rate;
> + return cd;
> +}
> +
> +static unsigned int atmel_calc_fidi(struct uart_port *port,
> + struct serial_iso7816 *iso7816conf)
> +{
> + u64 fidi = 0;
> +
> + if (iso7816conf->sc_fi && iso7816conf->sc_di) {
> + fidi = (u64)iso7816conf->sc_fi;
> + do_div(fidi, iso7816conf->sc_di);
> + }
> + return (u32)fidi;
> +}
> +
> +/* Enable or disable the iso7816 support */
> +/* Called with interrupts disabled */
> +static int atmel_config_iso7816(struct uart_port *port,
> + struct serial_iso7816 *iso7816conf)
> +{
> + struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
> + unsigned int mode, t;
> + unsigned int cd, fidi;
> + int ret = 0;
> +
> + /* Disable RX and TX */
> + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RXDIS | ATMEL_US_TXDIS);
> + /* Disable interrupts */
> + atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask);
> +
> + mode = atmel_uart_readl(port, ATMEL_US_MR);
> +
> + if (iso7816conf->flags & SER_ISO7816_ENABLED) {
> + mode &= ~ATMEL_US_USMODE;
> +
> + if ((iso7816conf->flags & SER_ISO7816_T_PARAM)
> + == SER_ISO7816_T(0)) {
> + mode |= ATMEL_US_USMODE_ISO7816_T0;
> + t = 0;
> + } else if ((iso7816conf->flags & SER_ISO7816_T_PARAM)
> + == SER_ISO7816_T(1)) {
> + mode |= ATMEL_US_USMODE_ISO7816_T1;
> + t = 1;
> + } else {
> + dev_warn(port->dev, "ISO7816 Type not supported. Resetting\n");
> + memset(iso7816conf, 0, sizeof(struct serial_iso7816));
> + goto err_out;
> + }
> +
> + dev_dbg(port->dev, "Setting USART to ISO7816 mode T%d\n", t);
> +
> + mode &= ~(ATMEL_US_USCLKS | ATMEL_US_CHRL
> + | ATMEL_US_NBSTOP | ATMEL_US_PAR);
This could be merged in the mode &= line above.

> +
> + /* NACK configuration */
> + if ((iso7816conf->flags & SER_ISO7816_T_PARAM)
> + == SER_ISO7816_T(0))
> + mode |= ATMEL_US_DSNACK;
> + else
> + mode |= ATMEL_US_INACK;
This could be also part of the if () above.

> + /* select mck clock, and output */
> + mode |= ATMEL_US_USCLKS_MCK | ATMEL_US_CLKO;
> + /* set parity for normal/inverse mode + max iterations */
> + mode |= ATMEL_US_PAR_EVEN | ATMEL_US_NBSTOP_1 | (3 << 24);
Is this really needed ?
In the documentation, I found:
"The configuration is 8 data bits, even parity and 1 or 2 stop bits,
regardless of the values programmed in the CHRL, MODE9, PAR and CHMODE
fields."
And, for MAX_ITERATIONS, could you add a macro instead of (x << 24) ?
(ATMEL_US_MAX_ITER mask is already defined).
And why 3 ? Should the user-space be allowed to control the max
automatic iteration ? or is it more like a "same-value-for-every-one"
thing ?

> +
> + cd = atmel_calc_cd(port, iso7816conf);
> + fidi = atmel_calc_fidi(port, iso7816conf);
> + if (fidi < 0) {
I guess you meant (fidi == 0)
Because fidi is unsigned and atmel_calc_fidi() returns also an unsigned.

> + dev_warn(port->dev, "ISO7816 fidi = 0, Generator generates no signal\n");
> + } else if (fidi == 1 || fidi == 2) {
> + dev_err(port->dev, "ISO7816 fidi = %u, value not supported\n", fidi);
> + ret = -EINVAL;
> + goto err_out;
> + }
And you may also want to check upper values ( <2048 or <65536, depending
on the SoC)

> +
> + if (!(port->iso7816.flags & SER_ISO7816_ENABLED)) {
> + /* port not yet in iso7816 mode: store configuration */
> + atmel_port->backup_mode = atmel_uart_readl(port, ATMEL_US_MR);
> + atmel_port->backup_brgr = atmel_uart_readl(port, ATMEL_US_BRGR);
> + }
> +
> + /* Actually set ISO7816 mode */
> + atmel_uart_writel(port, ATMEL_US_TTGR, iso7816conf->tg);
iso7816conf->tg comes from user-space unchecked. AFAIK, max value is 255

> + atmel_uart_writel(port, ATMEL_US_BRGR, cd);
> + atmel_uart_writel(port, ATMEL_US_FIDIR, fidi);
> +
> + atmel_port->tx_done_mask = ATMEL_US_TXEMPTY | ATMEL_US_NACK | ATMEL_US_ITERATION;
> + } else {
> + dev_dbg(port->dev, "Setting UART to RS232\n");
> + /* back to last RS232 settings */
> + mode = atmel_port->backup_mode;
> + memset(iso7816conf, 0, sizeof(struct serial_iso7816));
> + atmel_uart_writel(port, ATMEL_US_TTGR, 0);
> + atmel_uart_writel(port, ATMEL_US_BRGR, atmel_port->backup_brgr);
> + atmel_uart_writel(port, ATMEL_US_FIDIR, 0x174);
> +
> + if (atmel_use_pdc_tx(port))
> + atmel_port->tx_done_mask = ATMEL_US_ENDTX |
> + ATMEL_US_TXBUFE;
> + else
> + atmel_port->tx_done_mask = ATMEL_US_TXRDY;
> + }
> +
> + port->iso7816 = *iso7816conf;
> +
> + atmel_uart_writel(port, ATMEL_US_MR, mode);
> +
> +err_out:
> + /* Enable interrupts */
> + atmel_uart_writel(port, ATMEL_US_IER, atmel_port->tx_done_mask);
> + /* Enable RX and TX */
> + atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RXEN | ATMEL_US_TXEN);
Is it all right to enable RX/TX unconditionally here ?

> +
> + return ret;
> +}
> +
> /*
> * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
> */
> @@ -481,8 +610,9 @@ static void atmel_stop_tx(struct uart_port *port)
> /* Disable interrupts */
> atmel_uart_writel(port, ATMEL_US_IDR, atmel_port->tx_done_mask);
>
> - if ((port->rs485.flags & SER_RS485_ENABLED) &&
> - !(port->rs485.flags & SER_RS485_RX_DURING_TX))
> + if (((port->rs485.flags & SER_RS485_ENABLED) &&
> + !(port->rs485.flags & SER_RS485_RX_DURING_TX)) ||
> + port->iso7816.flags & SER_ISO7816_ENABLED)
> atmel_start_rx(port);
> }
>
> @@ -500,8 +630,9 @@ static void atmel_start_tx(struct uart_port *port)
> return;
>
> if (atmel_use_pdc_tx(port) || atmel_use_dma_tx(port))
> - if ((port->rs485.flags & SER_RS485_ENABLED) &&
> - !(port->rs485.flags & SER_RS485_RX_DURING_TX))
> + if (((port->rs485.flags & SER_RS485_ENABLED) &&
> + !(port->rs485.flags & SER_RS485_RX_DURING_TX)) ||
> + port->iso7816.flags & SER_ISO7816_ENABLED)
> atmel_stop_rx(port);
>
> if (atmel_use_pdc_tx(port))
> @@ -799,8 +930,9 @@ static void atmel_complete_tx_dma(void *arg)
> */
> if (!uart_circ_empty(xmit))
> atmel_tasklet_schedule(atmel_port, &atmel_port->tasklet_tx);
> - else if ((port->rs485.flags & SER_RS485_ENABLED) &&
> - !(port->rs485.flags & SER_RS485_RX_DURING_TX)) {
> + else if (((port->rs485.flags & SER_RS485_ENABLED) &&
> + !(port->rs485.flags & SER_RS485_RX_DURING_TX)) ||
> + port->iso7816.flags & SER_ISO7816_ENABLED) {
> /* DMA done, stop TX, start RX for RS485 */
> atmel_start_rx(port);
> }
> @@ -1281,6 +1413,9 @@ atmel_handle_status(struct uart_port *port, unsigned int pending,
> wake_up_interruptible(&port->state->port.delta_msr_wait);
> }
> }
> +
> + if (pending & (ATMEL_US_NACK | ATMEL_US_ITERATION))
> + dev_dbg(port->dev, "ISO7816 ERROR (0x%08x)\n", pending);
> }
>
> /*
> @@ -1373,8 +1508,9 @@ static void atmel_tx_pdc(struct uart_port *port)
> atmel_uart_writel(port, ATMEL_US_IER,
> atmel_port->tx_done_mask);
> } else {
> - if ((port->rs485.flags & SER_RS485_ENABLED) &&
> - !(port->rs485.flags & SER_RS485_RX_DURING_TX)) {
> + if (((port->rs485.flags & SER_RS485_ENABLED) &&
> + !(port->rs485.flags & SER_RS485_RX_DURING_TX)) ||
> + port->iso7816.flags & SER_ISO7816_ENABLED) {
> /* DMA done, stop TX, start RX for RS485 */
> atmel_start_rx(port);
> }
> @@ -2099,6 +2235,17 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
> atmel_uart_writel(port, ATMEL_US_TTGR,
> port->rs485.delay_rts_after_send);
> mode |= ATMEL_US_USMODE_RS485;
> + } else if (port->iso7816.flags & SER_ISO7816_ENABLED) {
> + atmel_uart_writel(port, ATMEL_US_TTGR, port->iso7816.tg);
> + /* select mck clock, and output */
> + mode |= ATMEL_US_USCLKS_MCK | ATMEL_US_CLKO;
> + /* set max iterations */
> + mode |= (3 << 24);
Same remark for macro / hardcoded value.

> + if ((port->iso7816.flags & SER_ISO7816_T_PARAM)
> + == SER_ISO7816_T(0))
> + mode |= ATMEL_US_USMODE_ISO7816_T0;
> + else
> + mode |= ATMEL_US_USMODE_ISO7816_T1;
> } else if (termios->c_cflag & CRTSCTS) {
> /* RS232 with hardware handshake (RTS/CTS) */
> if (atmel_use_fifo(port) &&
> @@ -2175,7 +2322,8 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
> }
> quot = cd | fp << ATMEL_US_FP_OFFSET;
>
> - atmel_uart_writel(port, ATMEL_US_BRGR, quot);
> + if (!(port->iso7816.flags & SER_ISO7816_ENABLED))
> + atmel_uart_writel(port, ATMEL_US_BRGR, quot);
> atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
> atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
> atmel_port->tx_stopped = false;
> @@ -2355,6 +2503,7 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
> port->mapbase = pdev->resource[0].start;
> port->irq = pdev->resource[1].start;
> port->rs485_config = atmel_config_rs485;
> + port->iso7816_config = atmel_config_iso7816;
> port->membase = NULL;
>
> memset(&atmel_port->rx_ring, 0, sizeof(atmel_port->rx_ring));
> @@ -2379,7 +2528,8 @@ static int atmel_init_port(struct atmel_uart_port *atmel_port,
> }
>
> /* Use TXEMPTY for interrupt when rs485 else TXRDY or ENDTX|TXBUFE */
> - if (port->rs485.flags & SER_RS485_ENABLED)
> + if (port->rs485.flags & SER_RS485_ENABLED ||
> + port->iso7816.flags & SER_ISO7816_ENABLED)
please update the comment above.

> atmel_port->tx_done_mask = ATMEL_US_TXEMPTY;
> else if (atmel_use_pdc_tx(port)) {
> port->fifosize = PDC_BUFFER_SIZE;
> diff --git a/drivers/tty/serial/atmel_serial.h b/drivers/tty/serial/atmel_serial.h
> index ba3a2437cde4..fff51f5fe8bc 100644
> --- a/drivers/tty/serial/atmel_serial.h
> +++ b/drivers/tty/serial/atmel_serial.h
> @@ -124,7 +124,8 @@
> #define ATMEL_US_TTGR 0x28 /* Transmitter Timeguard Register */
> #define ATMEL_US_TG GENMASK(7, 0) /* Timeguard Value */
>
> -#define ATMEL_US_FIDI 0x40 /* FI DI Ratio Register */
> +#define ATMEL_US_FIDIR 0x40 /* FI DI Ratio Register */
> +#define ATMEL_US_FIDI GENMASK(15, 0) /* FIDI ratio */
> #define ATMEL_US_NER 0x44 /* Number of Errors Register */
> #define ATMEL_US_IF 0x4c /* IrDA Filter Register */
>
>

Thanks !

Richard.

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