From mboxrd@z Thu Jan  1 00:00:00 1970
From: thara gopinath <thara@ti.com>
Subject: [PM-OPP][PATCH] OMAP: Modifying the frequency comparison logic.
Date: Sat, 14 Aug 2010 09:28:12 +0530
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Cc: khilman@deeprootsystems.com, nm@ti.com, Thara Gopinath <thara@ti.com>

From: Thara Gopinath <thara@ti.com>

In the current opp layer the frequency matching API's
tries to match the exact frequency passed in Hz. This leads
to problems in cases where dplls are locked to slightly differnet
frequencies due to sys clock speed or optimum M,N values.
Consider the following scenario
	a. dpll_x is supposed to be locked at 266Mhz but is
	   actually att 266.045 Mhz due to above mentioned reasons.
	b. The opp table has the entry as 266000000 hz.
	c. The user does a clk_get_rate(dpll_x) and passes the
	  corresponding rate <rate> into the opp API's to get back
	  a opp table entry.
	d. In this scenario if  the user has called into
	   opp_find_freq_exact it will return an error.
	   If the user has called into opp_find_freq_ceil
	   it will either return the opp entry corresponding
	   to the next higher frequency in the opp table
	   or return an error if 266 Mhz is the last entry
	   in the table.

The above is not correct as we expect the framework to return back
the opp table entry corresponding to 266 Mhz.

Now there are two ways of fixing this issue.
	a. Put the correct dpll lock frequency in the opp table.
	   This means opp table will now have entries like 266045000 hz.
	   But this is not scalable as these dpll lock frequencies
	   can change slightly based on sys clk speeds. Like for eg
	   at sys clk speed 38.4 Mhz we will able to get 266.045 Mhz
	   where as at sys clk speed 26 Mhz we will be able to get
	   onyl 266.124 Mhz etc. So depending on the platform we
	   will have to start changing the opp table.

	b. Do the comparison in Mhz in the opp layer rather than in Hz.
	   This would mean we will divide the rate passed into the opp layer
	  API and the rates stored in the opp tables by 1000000 to get the
	  rates in Mhz and do the necessary comparision. In this approach any
	  vague frequency like 266.045Mhz will get mapped to 266 Mhz in the
	  opp table. But if the passed rate is 267 Mhz, the opp framework
	  will still rerturn an error or the next highest opp table entry

This patch implements solution b. The scenario mentioned above is
esp true for OMAP4 dpll_iva where we do end up with such weird frequencies
due to sys clk being at 38.4 Mhz.

Signed-off-by: Thara Gopinath <thara@ti.com>
---
 arch/arm/plat-omap/opp.c |   37 ++++++++++++++++++++++++++-----------
 1 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/arch/arm/plat-omap/opp.c b/arch/arm/plat-omap/opp.c
index b9b7bda..ba7a554 100644
--- a/arch/arm/plat-omap/opp.c
+++ b/arch/arm/plat-omap/opp.c
@@ -212,15 +212,20 @@ struct omap_opp *opp_find_freq_exact(struct device *dev,
 {
 	struct device_opp *dev_opp;
 	struct omap_opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+	unsigned long req_freq = freq / 1000000;
 
 	dev_opp = find_device_opp(dev);
 	if (IS_ERR(dev_opp))
 		return opp;
 
 	list_for_each_entry(temp_opp, &dev_opp->opp_list, node) {
-		if (temp_opp->enabled && temp_opp->rate == freq) {
-			opp = temp_opp;
-			break;
+		if (temp_opp->enabled) {
+			unsigned long rate = temp_opp->rate / 1000000;
+
+			if (rate == req_freq) {
+				opp = temp_opp;
+				break;
+			}
 		}
 	}
 
@@ -258,16 +263,21 @@ struct omap_opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq)
 {
 	struct device_opp *dev_opp;
 	struct omap_opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+	unsigned long req_freq = *freq / 1000000;
 
 	dev_opp = find_device_opp(dev);
 	if (IS_ERR(dev_opp))
 		return opp;
 
 	list_for_each_entry(temp_opp, &dev_opp->opp_list, node) {
-		if (temp_opp->enabled && temp_opp->rate >= *freq) {
-			opp = temp_opp;
-			*freq = opp->rate;
-			break;
+		if (temp_opp->enabled) {
+			unsigned long rate = temp_opp->rate / 1000000;
+
+			if (rate >= req_freq) {
+				opp = temp_opp;
+				*freq = opp->rate;
+				break;
+			}
 		}
 	}
 
@@ -305,16 +315,21 @@ struct omap_opp *opp_find_freq_floor(struct device *dev, unsigned long *freq)
 {
 	struct device_opp *dev_opp;
 	struct omap_opp *temp_opp, *opp = ERR_PTR(-ENODEV);
+	unsigned long req_freq = *freq / 1000000;
 
 	dev_opp = find_device_opp(dev);
 	if (IS_ERR(dev_opp))
 		return opp;
 
 	list_for_each_entry_reverse(temp_opp, &dev_opp->opp_list, node) {
-		if (temp_opp->enabled && temp_opp->rate <= *freq) {
-			opp = temp_opp;
-			*freq = opp->rate;
-			break;
+		if (temp_opp->enabled) {
+			unsigned long rate = temp_opp->rate / 1000000;
+
+			if (rate <= req_freq) {
+				opp = temp_opp;
+				*freq = opp->rate;
+				break;
+			}
 		}
 	}
 
-- 
1.7.1.GIT