Re: [PATCH net-next v11 13/14] dpll: zl3073x: Add support to get/set frequency on input pins

On 19. 06. 25 2:15 odp., Vadim Fedorenko wrote:

On 19/06/2025 12:15, Paolo Abeni wrote:

quoted

On 6/16/25 10:14 PM, Ivan Vecera wrote:

quoted

+/**
+ * zl3073x_dpll_input_ref_frequency_get - get input reference frequency
+ * @zldpll: pointer to zl3073x_dpll
+ * @ref_id: reference id
+ * @frequency: pointer to variable to store frequency
+ *
+ * Reads frequency of given input reference.
+ *
+ * Return: 0 on success, <0 on error
+ */
+static int
+zl3073x_dpll_input_ref_frequency_get(struct zl3073x_dpll *zldpll, u8 ref_id,
+                     u32 *frequency)
+{
+    struct zl3073x_dev *zldev = zldpll->dev;
+    u16 base, mult, num, denom;
+    int rc;
+
+    guard(mutex)(&zldev->multiop_lock);
+
+    /* Read reference configuration */
+    rc = zl3073x_mb_op(zldev, ZL_REG_REF_MB_SEM, ZL_REF_MB_SEM_RD,
+               ZL_REG_REF_MB_MASK, BIT(ref_id));
+    if (rc)
+        return rc;
+
+    /* Read registers to compute resulting frequency */
+    rc = zl3073x_read_u16(zldev, ZL_REG_REF_FREQ_BASE, &base);
+    if (rc)
+        return rc;
+    rc = zl3073x_read_u16(zldev, ZL_REG_REF_FREQ_MULT, &mult);
+    if (rc)
+        return rc;
+    rc = zl3073x_read_u16(zldev, ZL_REG_REF_RATIO_M, &num);
+    if (rc)
+        return rc;
+    rc = zl3073x_read_u16(zldev, ZL_REG_REF_RATIO_N, &denom);
+    if (rc)
+        return rc;
+
+    /* Sanity check that HW has not returned zero denominator */
+    if (!denom) {
+        dev_err(zldev->dev,
+            "Zero divisor for ref %u frequency got from device\n",
+            ref_id);
+        return -EINVAL;
+    }
+
+    /* Compute the frequency */
+    *frequency = base * mult * num / denom;

As base, mult, num and denom are u16, the above looks like integer
overflow prone.

I think you should explicitly cast to u64, and possibly use a u64 frequency.

I might be a good idea to use mul_u64_u32_div together with mul_u32_u32?
These macroses will take care of overflow on 32bit platforms as well.

Will fix

Thanks for tip.

Ivan

quoted

/P