Re: [PATCH V6 XRT Alveo 16/20] fpga: xrt: clock driver

On 05/13/2021 08:48 AM, Tom Rix wrote:

quoted

+
+static int get_freq(struct clock *clock, u16 *freq)
+{

quoted

+
+     /*
+      * Multiply both numerator (mul0) and the denominator (div1) with
+      * 1000 to account for fractional portion of divider
+      */
+
+     div1 *= 1000;
+     div1 += div_frac1;
+     div0 *= div1;
+     mul0 *= 1000;
+     if (div0 == 0) {
+             CLOCK_ERR(clock, "clockwiz 0 divider");

This prevents a divide by zero, but returns 0 without setting freq

A -EINVAL should be returned or freq initialized to some default value

Sure.

quoted

+             return 0;
+     }
+
+     input = mul0 * 100;
+     do_div(input, div0);
+     *freq = (u16)input;
+
+     return 0;
+}
+

+
+static int clock_verify_freq(struct clock *clock)
+{
+     u32 lookup_freq, clock_freq_counter, request_in_khz, tolerance;
+     int err = 0;
+     u16 freq;
+
+     mutex_lock(&clock->clock_lock);
+
+     err = get_freq(clock, &freq);
+     if (err) {
+             xrt_err(clock->xdev, "get freq failed, %d", err);
+             goto end;
+     }
+
+     err = get_freq_counter(clock, &clock_freq_counter);
+     if (err) {
+             xrt_err(clock->xdev, "get freq counter failed, %d", err);
+             goto end;
+     }
+
+     lookup_freq = find_matching_freq(freq, frequency_table,
+ ARRAY_SIZE(frequency_table));

I am running v6 through clang's static analyzer, it shows a problem here

drivers/fpga/xrt/lib/xleaf/clock.c:474:16: warning: 1st function call
argument is an uninitialized value
        lookup_freq = find_matching_freq(freq, frequency_table,
                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

See problem with get_freq above

Sure.

Thanks,
Lizhi

Tom