/*
 * \brief  Base UART driver for the Texas instruments TL16C750 module
 * \author Martin stein
 * \date   2011-10-17
 */

/*
 * Copyright (C) 2011-2017 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU Affero General Public License version 3.
 */

#ifndef _INCLUDE__SPEC__TL16C750__DRIVERS__UART_BASE_H_
#define _INCLUDE__SPEC__TL16C750__DRIVERS__UART_BASE_H_

/* Genode includes */
#include <util/mmio.h>

namespace Genode { class Tl16c750_base; }


/**
 * Base driver Texas instruments TL16C750 UART module
 *
 * In contrast to the abilities of the TL16C750, this driver targets only
 * the basic UART functionalities.
 */
class Genode::Tl16c750_base : public Mmio
{
	protected:
		/**
		* Least significant divisor part
		*/
		struct Uart_dll : Register<0x0, 32>
		{
			struct Clock_lsb : Bitfield<0, 8> { };
		};

		/**
		* Transmit holding register
		*/
		struct Uart_thr : Register<0x0, 32>
		{
			struct Thr : Bitfield<0, 8> { };
		};

		/**
		 * Receiver holding register
		 */
		struct Uart_rhr : Register<0x0, 32>
		{
			struct Rhr : Bitfield<0, 8> { };
		};

		/**
		* Most significant divisor part
		*/
		struct Uart_dlh : Register<0x4, 32>
		{
			struct Clock_msb : Bitfield<0, 6> { };
		};

		/**
		* Interrupt enable register
		*/
		struct Uart_ier : Register<0x4, 32>
		{
			struct Rhr_it : Bitfield<0, 1> { };
			struct Thr_it : Bitfield<1, 1> { };
			struct Line_sts_it : Bitfield<2, 1> { };
			struct Modem_sts_it : Bitfield<3, 1> { };
			struct Sleep_mode : Bitfield<4, 1> { };
			struct Xoff_it : Bitfield<5, 1> { };
			struct Rts_it : Bitfield<6, 1> { };
			struct Cts_it : Bitfield<7, 1> { };
		};

		/**
		 * Interrupt identification register
		 */
		struct Uart_iir : Register<0x8, 32>
		{
			struct It_pending : Bitfield<0, 1> { };
		};

		/**
		* FIFO control register
		*/
		struct Uart_fcr : Register<0x8, 32>
		{
			struct Fifo_enable   : Bitfield<0, 1> { };
		};

		/**
		* Line control register
		*/
		struct Uart_lcr : Register<0xc, 32>
		{
			struct Char_length : Bitfield<0, 2>
			{
				enum { _8_BIT = 3 };
			};
			struct Nb_stop : Bitfield<2, 1>
			{
				enum { _1_STOP_BIT = 0 };
			};
			struct Parity_en : Bitfield<3, 1> { };
			struct Break_en  : Bitfield<6, 1> { };
			struct Div_en    : Bitfield<7, 1> { };
			struct Reg_mode  : Bitfield<0, 8>
			{
				enum { OPERATIONAL = 0, CONFIG_A = 0x80, CONFIG_B = 0xbf };
			};
		};

		/**
		* Modem control register
		*/
		struct Uart_mcr : Register<0x10, 32>
		{
			struct Tcr_tlr : Bitfield<6, 1> { };
		};

		/**
		* Line status register
		*/
		struct Uart_lsr : Register<0x14, 32>
		{
			struct Rx_fifo_empty : Bitfield<0, 1> { };
			struct Tx_fifo_empty : Bitfield<5, 1> { };
		};

		/**
		* Mode definition register 1
		*/
		struct Uart_mdr1 : Register<0x20, 32>
		{
			struct Mode_select : Bitfield<0, 3>
			{
				enum { UART_16X = 0, DISABLED = 7 };
			};
		};

		/**
		* System control register
		*/
		struct Uart_sysc : Register<0x54, 32>
		{
			struct Softreset : Bitfield<1, 1> { };
		};

		/**
		* System status register
		*/
		struct Uart_syss : Register<0x58, 32>
		{
			struct Resetdone : Bitfield<0, 1> { };
		};
		
		void _init(unsigned long const clock, unsigned long const baud_rate)
		{
			/* disable UART */
			write<Uart_mdr1::Mode_select>(Uart_mdr1::Mode_select::DISABLED);

			/* enable access to 'Uart_fcr' and 'Uart_ier' */
			write<Uart_lcr::Reg_mode>(Uart_lcr::Reg_mode::OPERATIONAL);

			/*
			 * Configure FIFOs, we don't use any interrupts or DMA,
			 * thus FIFO trigger and DMA configurations are dispensable.
			 */
			write<Uart_fcr::Fifo_enable>(1);

			/* disable interrupts and sleep mode */
			write<Uart_ier>(Uart_ier::Rhr_it::bits(0)
			              | Uart_ier::Thr_it::bits(0)
			              | Uart_ier::Line_sts_it::bits(0)
			              | Uart_ier::Modem_sts_it::bits(0)
			              | Uart_ier::Sleep_mode::bits(0)
			              | Uart_ier::Xoff_it::bits(0)
			              | Uart_ier::Rts_it::bits(0)
			              | Uart_ier::Cts_it::bits(0));

			/* enable access to 'Uart_dlh' and 'Uart_dll' */
			write<Uart_lcr::Reg_mode>(Uart_lcr::Reg_mode::CONFIG_B);

			/*
			 * Load the new divisor value (this driver solely uses
			 * 'UART_16X' mode)
			 */
			enum { UART_16X_DIVIDER_LOG2 = 4 };
			unsigned long const adjusted_br = baud_rate << UART_16X_DIVIDER_LOG2;
			double const divisor = (double)clock / adjusted_br;
			unsigned long const divisor_uint = (unsigned long)divisor;
			write<Uart_dll::Clock_lsb>(divisor_uint);
			write<Uart_dlh::Clock_msb>(divisor_uint>>Uart_dll::Clock_lsb::WIDTH);

			/*
			 * Configure protocol formatting and thereby return to
			 * operational mode.
			 */
			write<Uart_lcr>(Uart_lcr::Char_length::bits(Uart_lcr::Char_length::_8_BIT)
			              | Uart_lcr::Nb_stop::bits(Uart_lcr::Nb_stop::_1_STOP_BIT)
			              | Uart_lcr::Parity_en::bits(0)
			              | Uart_lcr::Break_en::bits(0)
			              | Uart_lcr::Div_en::bits(0));

			/*
			 * Switch to UART mode, we don't use hardware or software flow
			 * control, thus according configurations are dispensable
			 */
			write<Uart_mdr1::Mode_select>(Uart_mdr1::Mode_select::UART_16X);
		}

	public:
		/**
		 * Constructor
		 *
		 * \param  base       MMIO base address
		 * \param  clock      reference clock
		 * \param  baud_rate  targeted baud rate
		 */
		Tl16c750_base(addr_t const base, unsigned long const clock,
		              unsigned long const baud_rate) : Mmio(base)
		{
			/* reset and init UART */
			write<Uart_sysc::Softreset>(1);
			while (!read<Uart_syss::Resetdone>()) ;
			_init(clock, baud_rate);
		}

		/**
		 * Transmit ASCII char 'c'
		 */
		void put_char(char const c)
		{
			/* wait as long as the transmission buffer is full */
			while (!read<Uart_lsr::Tx_fifo_empty>()) ;

			/* transmit character */
			write<Uart_thr::Thr>(c);
		}
};

#endif /* _INCLUDE__SPEC__TL16C750__DRIVERS__UART_BASE_H_ */