Re: [PATCH v1 5/7] drivers: i2c: use i2c frequency table

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Hi,

kernel test robot noticed the following build warnings:

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/warp5tw-gmail-com/i2c-npcm-correct-the-read-write-operation-procedure/20240807-182210
base:   https://git.kernel.org/pub/scm/linux/kernel/git/andi.shyti/linux.git i2c/i2c-host
patch link:    https://lore.kernel.org/r/20240807100244.16872-6-kfting%40nuvoton.com
patch subject: [PATCH v1 5/7] drivers: i2c: use i2c frequency table
config: arm-randconfig-r073-20240812 (https://download.01.org/0day-ci/archive/20240813/202408130818.FgDP5uNm-lkp@xxxxxxxxx/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project f86594788ce93b696675c94f54016d27a6c21d18)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@xxxxxxxxx>
| Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
| Closes: https://lore.kernel.org/r/202408130818.FgDP5uNm-lkp@xxxxxxxxx/

New smatch warnings:
drivers/i2c/busses/i2c-npcm7xx.c:1956 npcm_i2c_init_clk() error: buffer overflow 'smb_timing' 21 <= 21 (assuming for loop doesn't break)
drivers/i2c/busses/i2c-npcm7xx.c:1973 npcm_i2c_init_clk() error: buffer overflow 'smb_timing' 17 <= 21

Old smatch warnings:
drivers/i2c/busses/i2c-npcm7xx.c:752 npcm_i2c_slave_enable() error: buffer overflow 'npcm_i2caddr' 2 <= 9
drivers/i2c/busses/i2c-npcm7xx.c:1960 npcm_i2c_init_clk() error: buffer overflow 'smb_timing' 21 <= 21 (assuming for loop doesn't break)
drivers/i2c/busses/i2c-npcm7xx.c:1974 npcm_i2c_init_clk() error: buffer overflow 'smb_timing' 17 <= 21
drivers/i2c/busses/i2c-npcm7xx.c:1976 npcm_i2c_init_clk() error: buffer overflow 'smb_timing' 17 <= 21
drivers/i2c/busses/i2c-npcm7xx.c:1979 npcm_i2c_init_clk() error: buffer overflow 'smb_timing' 21 <= 21 (assuming for loop doesn't break)

vim +1956 drivers/i2c/busses/i2c-npcm7xx.c

56a1485b102ed1 Tali Perry          2020-05-27  1919  static int npcm_i2c_init_clk(struct npcm_i2c *bus, u32 bus_freq_hz)
56a1485b102ed1 Tali Perry          2020-05-27  1920  {
a946fe9698f261 Tyrone Ting         2024-08-07  1921  	struct  SMB_TIMING_T *smb_timing;
a946fe9698f261 Tyrone Ting         2024-08-07  1922  	u8   scl_table_cnt = 0, table_size = 0;
a946fe9698f261 Tyrone Ting         2024-08-07  1923  
56a1485b102ed1 Tali Perry          2020-05-27  1924  	u8   fast_mode = 0;
56a1485b102ed1 Tali Perry          2020-05-27  1925  	u32  src_clk_khz;
56a1485b102ed1 Tali Perry          2020-05-27  1926  	u32  bus_freq_khz;
56a1485b102ed1 Tali Perry          2020-05-27  1927  
56a1485b102ed1 Tali Perry          2020-05-27  1928  	src_clk_khz = bus->apb_clk / 1000;
56a1485b102ed1 Tali Perry          2020-05-27  1929  	bus_freq_khz = bus_freq_hz / 1000;
56a1485b102ed1 Tali Perry          2020-05-27  1930  	bus->bus_freq = bus_freq_hz;
56a1485b102ed1 Tali Perry          2020-05-27  1931  
a946fe9698f261 Tyrone Ting         2024-08-07  1932  	switch (bus_freq_hz) {
a946fe9698f261 Tyrone Ting         2024-08-07  1933  	case I2C_MAX_STANDARD_MODE_FREQ:
a946fe9698f261 Tyrone Ting         2024-08-07  1934  		smb_timing = SMB_TIMING_100KHZ;
a946fe9698f261 Tyrone Ting         2024-08-07  1935  		table_size = ARRAY_SIZE(SMB_TIMING_100KHZ);
a946fe9698f261 Tyrone Ting         2024-08-07  1936  		break;
a946fe9698f261 Tyrone Ting         2024-08-07  1937  	case I2C_MAX_FAST_MODE_FREQ:
a946fe9698f261 Tyrone Ting         2024-08-07  1938  		smb_timing = SMB_TIMING_400KHZ;
a946fe9698f261 Tyrone Ting         2024-08-07  1939  		table_size = ARRAY_SIZE(SMB_TIMING_400KHZ);
56a1485b102ed1 Tali Perry          2020-05-27  1940  		fast_mode = I2CCTL3_400K_MODE;
a946fe9698f261 Tyrone Ting         2024-08-07  1941  		break;
a946fe9698f261 Tyrone Ting         2024-08-07  1942  	case I2C_MAX_FAST_MODE_PLUS_FREQ:
a946fe9698f261 Tyrone Ting         2024-08-07  1943  		smb_timing = SMB_TIMING_1000KHZ;
a946fe9698f261 Tyrone Ting         2024-08-07  1944  		table_size = ARRAY_SIZE(SMB_TIMING_1000KHZ);
56a1485b102ed1 Tali Perry          2020-05-27  1945  		fast_mode = I2CCTL3_400K_MODE;
a946fe9698f261 Tyrone Ting         2024-08-07  1946  		break;
a946fe9698f261 Tyrone Ting         2024-08-07  1947  	default:
56a1485b102ed1 Tali Perry          2020-05-27  1948  		return -EINVAL;
56a1485b102ed1 Tali Perry          2020-05-27  1949  	}
56a1485b102ed1 Tali Perry          2020-05-27  1950  
a946fe9698f261 Tyrone Ting         2024-08-07  1951  	for (scl_table_cnt = 0 ; scl_table_cnt < table_size ; scl_table_cnt++)
a946fe9698f261 Tyrone Ting         2024-08-07  1952  		if (bus->apb_clk >= smb_timing[scl_table_cnt].core_clk)
a946fe9698f261 Tyrone Ting         2024-08-07  1953  			break;

The minimum smb_timing[scl_table_cnt].core_clk value is 10000000 or 20000000 so
I can't tell just from the context that we are always going to hit this break
statement.

a946fe9698f261 Tyrone Ting         2024-08-07  1954  
56a1485b102ed1 Tali Perry          2020-05-27  1955  	/* write sclfrq value. bits [6:0] are in I2CCTL2 reg */
a946fe9698f261 Tyrone Ting         2024-08-07 @1956  	iowrite8(FIELD_PREP(I2CCTL2_SCLFRQ6_0, smb_timing[scl_table_cnt].sclfrq & 0x7F),
                                                                                               ^^^^^^^^^^^^^^^^^^^^^^^^^

56a1485b102ed1 Tali Perry          2020-05-27  1957  		 bus->reg + NPCM_I2CCTL2);
56a1485b102ed1 Tali Perry          2020-05-27  1958  
56a1485b102ed1 Tali Perry          2020-05-27  1959  	/* bits [8:7] are in I2CCTL3 reg */
a946fe9698f261 Tyrone Ting         2024-08-07  1960  	iowrite8(fast_mode | FIELD_PREP(I2CCTL3_SCLFRQ8_7, (smb_timing[scl_table_cnt].sclfrq >> 7)
a946fe9698f261 Tyrone Ting         2024-08-07  1961  		 & 0x3),
56a1485b102ed1 Tali Perry          2020-05-27  1962  		 bus->reg + NPCM_I2CCTL3);
56a1485b102ed1 Tali Perry          2020-05-27  1963  
56a1485b102ed1 Tali Perry          2020-05-27  1964  	/* Select Bank 0 to access NPCM_I2CCTL4/NPCM_I2CCTL5 */
56a1485b102ed1 Tali Perry          2020-05-27  1965  	npcm_i2c_select_bank(bus, I2C_BANK_0);
56a1485b102ed1 Tali Perry          2020-05-27  1966  
56a1485b102ed1 Tali Perry          2020-05-27  1967  	if (bus_freq_hz >= I2C_MAX_FAST_MODE_FREQ) {
56a1485b102ed1 Tali Perry          2020-05-27  1968  		/*
56a1485b102ed1 Tali Perry          2020-05-27  1969  		 * Set SCL Low/High Time:
56a1485b102ed1 Tali Perry          2020-05-27  1970  		 * k1 = 2 * SCLLT7-0 -> Low Time  = k1 / 2
56a1485b102ed1 Tali Perry          2020-05-27  1971  		 * k2 = 2 * SCLLT7-0 -> High Time = k2 / 2
56a1485b102ed1 Tali Perry          2020-05-27  1972  		 */
a946fe9698f261 Tyrone Ting         2024-08-07 @1973  		iowrite8(smb_timing[scl_table_cnt].scllt, bus->reg + NPCM_I2CSCLLT);
a946fe9698f261 Tyrone Ting         2024-08-07  1974  		iowrite8(smb_timing[scl_table_cnt].sclht, bus->reg + NPCM_I2CSCLHT);
56a1485b102ed1 Tali Perry          2020-05-27  1975  
a946fe9698f261 Tyrone Ting         2024-08-07  1976  		iowrite8(smb_timing[scl_table_cnt].dbcnt, bus->reg + NPCM_I2CCTL5);
56a1485b102ed1 Tali Perry          2020-05-27  1977  	}
56a1485b102ed1 Tali Perry          2020-05-27  1978  
a946fe9698f261 Tyrone Ting         2024-08-07  1979  	iowrite8(smb_timing[scl_table_cnt].hldt, bus->reg + NPCM_I2CCTL4);
56a1485b102ed1 Tali Perry          2020-05-27  1980  
56a1485b102ed1 Tali Perry          2020-05-27  1981  	/* Return to Bank 1, and stay there by default: */
56a1485b102ed1 Tali Perry          2020-05-27  1982  	npcm_i2c_select_bank(bus, I2C_BANK_1);
56a1485b102ed1 Tali Perry          2020-05-27  1983  
56a1485b102ed1 Tali Perry          2020-05-27  1984  	return 0;
56a1485b102ed1 Tali Perry          2020-05-27  1985  }

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki





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