Re: [V5] tty: serial: qcom-geni-serial: Fix get_clk_div_rate() which otherwise could return a sub-optimal clock rate.

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On 7/14/2022 4:16 PM, Jiri Slaby wrote:
On 12. 07. 22, 14:45, Vijaya Krishna Nivarthi wrote:
...
+static unsigned long get_clk_div_rate(struct clk *clk, struct device *dev, +        unsigned int baud, unsigned int sampling_rate, unsigned int *clk_div)
+{
+    unsigned long ser_clk;
+    unsigned long desired_clk;
+
+    desired_clk = baud * sampling_rate;
+    if (!desired_clk) {
+        dev_dbg(dev, "Invalid frequency\n");
+        return 0;
      }
  -    *clk_div = ser_clk / desired_clk;
-    if (!(*clk_div))
-        *clk_div = 1;
+    /*
+     * try to find a clock rate within 2% tolerance, then within

"then within" ... "5" is missing, perhaps?


Yes :(

Will change.



+     */
+    ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 2);
+    if (!ser_clk)
+        ser_clk = find_clk_rate_in_tol(clk, desired_clk, clk_div, 5);
+
+    if (!ser_clk)
+        dev_err(dev, "Couldn't find suitable clock rate for %lu\n", desired_clk);
+    else
+        dev_dbg(dev, "desired_clk-%lu, ser_clk-%lu, clk_div-%u\n",
+                desired_clk, ser_clk, *clk_div);
        return ser_clk;
  }
@@ -1021,8 +1040,8 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
      if (ver >= QUP_SE_VERSION_2_5)
          sampling_rate /= 2;
  -    clk_rate = get_clk_div_rate(port->se.clk, baud,
-        sampling_rate, &clk_div);
+    clk_rate = get_clk_div_rate(port->se.clk, port->se.dev, baud,

Maybe worth passing whole geni_se (port->se) then?


but then geni_se is a struct; shall we pass port instead?

Alternately move logging to caller?

Thank you.



+                    sampling_rate, &clk_div);
      if (!clk_rate)
          goto out_restart_rx;

thanks,



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