Messages in this thread Patch in this message | | | Subject | Re: [PATCH v4 1/1] i2c: designware: use casting of u64 in clock multiplication to avoid overflow | Date | Tue, 20 Dec 2022 19:43:06 +0200 | From | "Hawa, Hanna" <> |
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On 12/20/2022 7:11 PM, Andy Shevchenko wrote: > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe. > > > > On Tue, Dec 20, 2022 at 04:48:06PM +0000, Hanna Hawa wrote: >> From: Lareine Khawaly <lareine@amazon.com> >> >> 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. > > ... > >> - return DIV_ROUND_CLOSEST(ic_clk * tSYMBOL, MICRO) - 8 + offset; >> + return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * tSYMBOL, MICRO) - 8 + >> + offset; > > Broken indentation. > > ... > >> - return DIV_ROUND_CLOSEST(ic_clk * (tSYMBOL + tf), MICRO) - 3 + offset; >> + return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * (tSYMBOL + tf), >> + MICRO) - 3 + offset; > > I would still go with 'MICRO) -' part to be on the previous line despite being > over 80, this is logical split which increases readability.
Okay.. will move the 'MICRO) -' one line before > >> - return DIV_ROUND_CLOSEST(ic_clk * (tLOW + tf), MICRO) - 1 + offset; >> + return DIV_ROUND_CLOSEST_ULL((u64)ic_clk * (tLOW + tf), MICRO) - 1 + >> + offset; > > Broken indentation.
Why it's broken indentation? I'm asking to know for the next time. The word 'offset' is not part of DIV_ROUND_CLOSEST_ULL parentheses. In wrong indentation the checkpatch shout about it, but it didn't happen with the above.
Does the below the correct indentation?
--- a/drivers/i2c/busses/i2c-designware-common.c +++ b/drivers/i2c/busses/i2c-designware-common.c @@ -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; }
> -- > With Best Regards, > Andy Shevchenko > >
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