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SubjectRe: [PATCH] clk: Add driver for the si544 clock generator chip
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On 15-03-18 11:35, Dan Carpenter wrote:
> Hi Mike,
>
> Thank you for the patch! Perhaps something to improve:
>
> [auto build test WARNING on v4.16-rc4]
> [also build test WARNING on next-20180314]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
> url: https://github.com/0day-ci/linux/commits/Mike-Looijmans/clk-Add-driver-for-the-si544-clock-generator-chip/20180314-122736
>
> smatch warnings:
> drivers/clk/clk-si544.c:188 si544_calc_muldiv() warn: impossible condition '((frequency * tmp) >= 10800000000) => (0-u32max >= 10800000000)'

Indeed, there's a u64 cast missing.

I've also missed that the hs_div cannot be odd when ls_div is non-zero.

I'll compose a v2 patch fixing these issues.

> # https://github.com/0day-ci/linux/commit/aba3d3de8751c1457bcf0b75bcc901f289a18426
> git remote add linux-review https://github.com/0day-ci/linux
> git remote update linux-review
> git checkout aba3d3de8751c1457bcf0b75bcc901f289a18426
> vim +188 drivers/clk/clk-si544.c
>
> aba3d3de Mike Looijmans 2018-03-13 168
> aba3d3de Mike Looijmans 2018-03-13 169 /* Calculate divider settings for a given frequency */
> aba3d3de Mike Looijmans 2018-03-13 170 static int si544_calc_muldiv(struct clk_si544_muldiv *settings,
> aba3d3de Mike Looijmans 2018-03-13 171 unsigned long frequency)
> aba3d3de Mike Looijmans 2018-03-13 172 {
> aba3d3de Mike Looijmans 2018-03-13 173 u64 vco;
> aba3d3de Mike Looijmans 2018-03-13 174 u32 ls_freq;
> aba3d3de Mike Looijmans 2018-03-13 175 u32 tmp;
> aba3d3de Mike Looijmans 2018-03-13 176 u8 res;
> aba3d3de Mike Looijmans 2018-03-13 177
> aba3d3de Mike Looijmans 2018-03-13 178 /* Determine the minimum value of LS_DIV and resulting target freq. */
> aba3d3de Mike Looijmans 2018-03-13 179 ls_freq = frequency;
> aba3d3de Mike Looijmans 2018-03-13 180 settings->ls_div_bits = 0;
> aba3d3de Mike Looijmans 2018-03-13 181
> aba3d3de Mike Looijmans 2018-03-13 182 if (frequency >= (FVCO_MIN / HS_DIV_MAX))
> aba3d3de Mike Looijmans 2018-03-13 183 settings->ls_div_bits = 0;
> aba3d3de Mike Looijmans 2018-03-13 184 else {
> aba3d3de Mike Looijmans 2018-03-13 185 res = 1;
> aba3d3de Mike Looijmans 2018-03-13 186 tmp = 2 * HS_DIV_MAX;
> aba3d3de Mike Looijmans 2018-03-13 187 while (tmp <= (HS_DIV_MAX * 32)) {
> aba3d3de Mike Looijmans 2018-03-13 @188 if ((frequency * tmp) >= FVCO_MIN)
> aba3d3de Mike Looijmans 2018-03-13 189 break;
> aba3d3de Mike Looijmans 2018-03-13 190 ++res;
> aba3d3de Mike Looijmans 2018-03-13 191 tmp <<= 1;
> aba3d3de Mike Looijmans 2018-03-13 192 }
> aba3d3de Mike Looijmans 2018-03-13 193 settings->ls_div_bits = res;
> aba3d3de Mike Looijmans 2018-03-13 194 ls_freq = frequency << res;
> aba3d3de Mike Looijmans 2018-03-13 195 }
> aba3d3de Mike Looijmans 2018-03-13 196
> aba3d3de Mike Looijmans 2018-03-13 197 /* Determine minimum HS_DIV by rounding up */
> aba3d3de Mike Looijmans 2018-03-13 198 vco = FVCO_MIN + ls_freq - 1;
> aba3d3de Mike Looijmans 2018-03-13 199 do_div(vco, ls_freq);
> aba3d3de Mike Looijmans 2018-03-13 200 settings->hs_div = vco;
> aba3d3de Mike Looijmans 2018-03-13 201 /* round up to even number if needed */
> aba3d3de Mike Looijmans 2018-03-13 202 if ((settings->hs_div > HS_DIV_MAX_ODD) && (settings->hs_div & 1))
> aba3d3de Mike Looijmans 2018-03-13 203 ++settings->hs_div;
> aba3d3de Mike Looijmans 2018-03-13 204 /* Calculate VCO frequency (in 10..12GHz range) */
> aba3d3de Mike Looijmans 2018-03-13 205 vco = (u64)ls_freq * settings->hs_div;
> aba3d3de Mike Looijmans 2018-03-13 206 /* Calculate the integer part of the feedback divider */
> aba3d3de Mike Looijmans 2018-03-13 207 tmp = do_div(vco, FXO);
> aba3d3de Mike Looijmans 2018-03-13 208 settings->fb_div_int = vco;
> aba3d3de Mike Looijmans 2018-03-13 209 /* And the fractional bits using the remainder */
> aba3d3de Mike Looijmans 2018-03-13 210 vco = (u64)tmp << 32;
> aba3d3de Mike Looijmans 2018-03-13 211 do_div(vco, FXO);
> aba3d3de Mike Looijmans 2018-03-13 212 settings->fb_div_frac = vco;
> aba3d3de Mike Looijmans 2018-03-13 213
> aba3d3de Mike Looijmans 2018-03-13 214 return 0;
> aba3d3de Mike Looijmans 2018-03-13 215 }
> aba3d3de Mike Looijmans 2018-03-13 216
>
> ---
> 0-DAY kernel test infrastructure Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all Intel Corporation
>



Kind regards,

Mike Looijmans
System Expert

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