[PATCH 3/3] tty: serial: uartps: Add support for uartps controller reset

[Pandey, Radhey Shyam]

> -----Original Message-----
> From: Manikanta Guntupalli <manikanta.guntupalli at amd.com>
> Sent: Friday, April 19, 2024 5:36 PM
> To: git (AMD-Xilinx) <git at amd.com>; gregkh at linuxfoundation.org;
> jirislaby at kernel.org; robh at kernel.org; krzk+dt at kernel.org;
> conor+dt at kernel.org; Simek, Michal <michal.simek at amd.com>;
> p.zabel at pengutronix.de; laurent.pinchart at ideasonboard.com; Pandey,
> Radhey Shyam <radhey.shyam.pandey at amd.com>; Gajjar, Parth
> <parth.gajjar at amd.com>; u.kleine-koenig at pengutronix.de;
> tglx at linutronix.de; julien.malik at unseenlabs.fr; ruanjinjie at huawei.com;
> linux-kernel at vger.kernel.org; linux-serial at vger.kernel.org;
> devicetree at vger.kernel.org; linux-arm-kernel at lists.infradead.org
> Cc: Goud, Srinivas <srinivas.goud at amd.com>; Datta, Shubhrajyoti
> <shubhrajyoti.datta at amd.com>; manion05gk at gmail.com; Guntupalli,
> Manikanta <manikanta.guntupalli at amd.com>
> Subject: [PATCH 3/3] tty: serial: uartps: Add support for uartps controller
> reset
> 
> Add support for an optional reset for the uartps controller using
> the reset driver. If the uartps node contains the "resets" property,
> then cdns_uart_startup performs uartps controller non-pulse out of reset
> and reset in exit path.
> 
> Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli at amd.com>
> ---
>  drivers/tty/serial/xilinx_uartps.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/tty/serial/xilinx_uartps.c
> b/drivers/tty/serial/xilinx_uartps.c
> index de3487206bcb..e45d6993ba05 100644
> --- a/drivers/tty/serial/xilinx_uartps.c
> +++ b/drivers/tty/serial/xilinx_uartps.c
> @@ -25,6 +25,7 @@
>  #include <linux/gpio.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/delay.h>
> +#include <linux/reset.h>
> 
>  #define CDNS_UART_TTY_NAME	"ttyPS"
>  #define CDNS_UART_NAME		"xuartps"
> @@ -198,6 +199,7 @@ MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-
> 255");
>   * @gpiod_rts:		Pointer to the gpio descriptor
>   * @rs485_tx_started:	RS485 tx state
>   * @tx_timer:		Timer for tx
> + * @rstc:		Pointer to the reset control
>   */
>  struct cdns_uart {
>  	struct uart_port	*port;
> @@ -211,6 +213,7 @@ struct cdns_uart {
>  	struct gpio_desc	*gpiod_rts;
>  	bool			rs485_tx_started;
>  	struct hrtimer		tx_timer;
> +	struct reset_control	*rstc;
>  };
>  struct cdns_platform_data {
>  	u32 quirks;
> @@ -948,6 +951,12 @@ static int cdns_uart_startup(struct uart_port *port)
> 
>  	is_brk_support = cdns_uart->quirks & CDNS_UART_RXBS_SUPPORT;
> 
> +	if (cdns_uart->rstc) {
> +		ret = reset_control_deassert(cdns_uart->rstc);

reset_control_deassert already has NULL check , then any need for this additional
if check?


> +		if (ret)
> +			return ret;
> +	}
> +
>  	uart_port_lock_irqsave(port, &flags);
> 
>  	/* Disable the TX and RX */
> @@ -1721,6 +1730,13 @@ static int cdns_uart_probe(struct platform_device
> *pdev)
>  		dev_err(&pdev->dev, "clock name 'ref_clk' is
> deprecated.\n");
>  	}
> 
> +	cdns_uart_data->rstc =
> devm_reset_control_get_optional_exclusive(&pdev->dev, NULL);
> +	if (IS_ERR(cdns_uart_data->rstc)) {
> +		rc = PTR_ERR(cdns_uart_data->rstc);
> +		dev_err_probe(&pdev->dev, rc, "Cannot get UART reset\n");
> +		goto err_out_unregister_driver;
> +	}
> +
>  	rc = clk_prepare_enable(cdns_uart_data->pclk);
>  	if (rc) {
>  		dev_err(&pdev->dev, "Unable to enable pclk clock.\n");
> @@ -1881,6 +1897,7 @@ static void cdns_uart_remove(struct
> platform_device *pdev)
>  	if (console_port == port)
>  		console_port = NULL;
>  #endif
> +	reset_control_assert(cdns_uart_data->rstc);
> 
>  	if (!--instances)
>  		uart_unregister_driver(cdns_uart_data->cdns_uart_driver);
> --
> 2.25.1