ast_i2c.c

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/* SPDX-License-Identifier: MIT */
/*
 * Copied from Linux drivers/gpu/drm/ast/ast_mode.c
 */
#include <delay.h>
#include <device/i2c_simple.h>
 
#include "ast_drv.h"
 
static struct ast_private *ast;
 
#define _GET_INDEX_REG(x) ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, (x))
#define ASPEED_BUS 0
 
static int get_clock(unsigned int bus)
{
        uint32_t val, val2, count, pass;
 
        count = 0;
        pass = 0;
        val = (_GET_INDEX_REG(0x10) >> 4) & 0x01;
        do {
                val2 = (_GET_INDEX_REG(0x10) >> 4) & 0x01;
                if (val == val2) {
                        pass++;
                } else {
                        pass = 0;
                        val = (_GET_INDEX_REG(0x10) >> 4) & 0x01;
                }
        } while ((pass < 5) && (count++ < 0x10000));
 
        return val & 1 ? 1 : 0;
}
 
static int get_data(unsigned int bus)
{
        uint32_t val, val2, count, pass;
 
        count = 0;
        pass = 0;
        val = (_GET_INDEX_REG(0x20) >> 5) & 0x01;
        do {
                val2 = (_GET_INDEX_REG(0x20) >> 5) & 0x01;
                if (val == val2) {
                        pass++;
                } else {
                        pass = 0;
                        val = (_GET_INDEX_REG(0x20) >> 5) & 0x01;
                }
        } while ((pass < 5) && (count++ < 0x10000));
 
        return val & 1 ? 1 : 0;
}
 
static void set_clock(unsigned int bus, int clock)
{
        int i;
        u8 ujcrb7, jtemp;
 
        for (i = 0; i < 0x10000; i++) {
                ujcrb7 = ((clock & 0x01) ? 0 : 1);
                ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0xf4, ujcrb7);
                jtemp = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x01);
                if (ujcrb7 == jtemp)
                        break;
        }
}
 
static void set_data(unsigned int bus, int data)
{
        int i;
        u8 ujcrb7, jtemp;
 
        for (i = 0; i < 0x10000; i++) {
                ujcrb7 = ((data & 0x01) ? 0 : 1) << 2;
                ast_set_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0xf1, ujcrb7);
                jtemp = ast_get_index_reg_mask(ast, AST_IO_CRTC_PORT, 0xb7, 0x04);
                if (ujcrb7 == jtemp)
                        break;
        }
}
 
static struct software_i2c_ops ast_ops = {
        .set_sda = set_data,
        .set_scl = set_clock,
        .get_sda = get_data,
        .get_scl = get_clock,
};
 
int ast_software_i2c_read(struct ast_private *ast_priv, uint8_t edid[128])
{
        struct software_i2c_ops *backup;
        int ret;
 
        backup = software_i2c[ASPEED_BUS];
 
        software_i2c[ASPEED_BUS] = &ast_ops;
 
        ast = ast_priv;
 
        /* Ast POST pulled SDA and SCL low, recover the bus to a known state */
        set_clock(ASPEED_BUS, 1);
        set_data(ASPEED_BUS, 1);
 
        udelay(100);
 
        /* Need to reset internal EEPROM counter to 0 */
        ret = i2c_read_bytes(ASPEED_BUS, 0x50, 0, edid, 128);
 
        software_i2c[ASPEED_BUS] = backup;
 
        return ret;
}