Commit c8c37bc5 authored by Lareine Khawaly's avatar Lareine Khawaly Committed by Wolfram Sang
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i2c: designware: use casting of u64 in clock multiplication to avoid overflow 



In functions i2c_dw_scl_lcnt() and i2c_dw_scl_hcnt() may have overflow
by depending on the values of the given parameters including the ic_clk.
For example in our use case where ic_clk is larger than one million,
multiplication of ic_clk * 4700 will result in 32 bit overflow.

Add cast of u64 to the calculation to avoid multiplication overflow, and
use the corresponding define for divide.

Fixes: 2373f6b9 ("i2c-designware: split of i2c-designware.c into core and bus specific parts")
Signed-off-by: default avatarLareine Khawaly <lareine@amazon.com>
Signed-off-by: default avatarHanna Hawa <hhhawa@amazon.com>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: default avatarJarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: default avatarWolfram Sang <wsa@kernel.org>
parent b7bfaa76

drivers/i2c/busses/i2c-designware-common.c

+6 −3
Original line number Diff line number Diff line
@@ -351,7 +351,8 @@ u32 i2c_dw_scl_hcnt(u32 ic_clk, u32 tSYMBOL, u32 tf, int cond, int offset) 
		 *

		 * If your hardware is free from tHD;STA issue, try this one.

		 */

		return DIV_ROUND_CLOSEST(ic_clk * tSYMBOL, MICRO) - 8 + offset;

		return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * tSYMBOL, MICRO) -

		       8 + offset;

	else

		/*

		 * Conditional expression:
@@ -367,7 +368,8 @@ u32 i2c_dw_scl_hcnt(u32 ic_clk, u32 tSYMBOL, u32 tf, int cond, int offset) 
		 * The reason why we need to take into account "tf" here,

		 * is the same as described in i2c_dw_scl_lcnt().

		 */

		return DIV_ROUND_CLOSEST(ic_clk * (tSYMBOL + tf), MICRO) - 3 + offset;

		return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * (tSYMBOL + tf), MICRO) -

		       3 + offset;

}



u32 i2c_dw_scl_lcnt(u32 ic_clk, u32 tLOW, u32 tf, int offset)
@@ -383,7 +385,8 @@ u32 i2c_dw_scl_lcnt(u32 ic_clk, u32 tLOW, u32 tf, int offset) 
	 * account the fall time of SCL signal (tf).  Default tf value

	 * should be 0.3 us, for safety.

	 */

	return DIV_ROUND_CLOSEST(ic_clk * (tLOW + tf), MICRO) - 1 + offset;

	return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * (tLOW + tf), MICRO) -

	       1 + offset;

}



int i2c_dw_set_sda_hold(struct dw_i2c_dev *dev)