[haiku-commits] haiku: hrev46957 - src/add-ons/accelerants/radeon_hd
- From: julian.harnath@xxxxxxxxxxxxxx
- To: haiku-commits@xxxxxxxxxxxxx
- Date: Sun, 2 Mar 2014 16:26:46 +0100 (CET)
hrev46957 adds 2 changesets to branch 'master'
old head: edf15527703bef4301932864d601f1e055adc6e0
new head: de26f2e76291e3e6953d950709617c57a76bbeaa
overview: http://cgit.haiku-os.org/haiku/log/?qt=range&q=de26f2e+%5Eedf1552
----------------------------------------------------------------------------
34d3dff: Fix feedback divider value approximation
* The rounding algorithm here expects to start with the 2 digits
after the decimal point in pll->feedbackDivFrac. Multiplying with
1000 instead of 100 filled it with 3 digits.
The last step then set the fractional part to zero because it was
still too large.
de26f2e: Make code a bit easier to read, add some comments
* No functional change intended
[ Julian Harnath <julian.harnath@xxxxxxxxxxxxxx> ]
----------------------------------------------------------------------------
1 file changed, 36 insertions(+), 8 deletions(-)
src/add-ons/accelerants/radeon_hd/pll.cpp | 44 ++++++++++++++++++++++-----
############################################################################
Commit: 34d3dff3f5caef59b67669535a6f535dcaad7827
URL: http://cgit.haiku-os.org/haiku/commit/?id=34d3dff
Author: Julian Harnath <julian.harnath@xxxxxxxxxxxxxx>
Date: Sun Mar 2 15:20:07 2014 UTC
Fix feedback divider value approximation
* The rounding algorithm here expects to start with the 2 digits
after the decimal point in pll->feedbackDivFrac. Multiplying with
1000 instead of 100 filled it with 3 digits.
The last step then set the fractional part to zero because it was
still too large.
----------------------------------------------------------------------------
diff --git a/src/add-ons/accelerants/radeon_hd/pll.cpp
b/src/add-ons/accelerants/radeon_hd/pll.cpp
index ec8a1f0..ce46b6d 100644
--- a/src/add-ons/accelerants/radeon_hd/pll.cpp
+++ b/src/add-ons/accelerants/radeon_hd/pll.cpp
@@ -374,7 +374,7 @@ pll_compute(pll_info* pll)
pll->feedbackDiv = pll->minFeedbackDiv;
pll->feedbackDivFrac
- = (1000 * pll->feedbackDivFrac) / pll->referenceFreq;
+ = (100 * pll->feedbackDivFrac) / pll->referenceFreq;
if (pll->feedbackDivFrac >= 5) {
pll->feedbackDivFrac -= 5;
############################################################################
Revision: hrev46957
Commit: de26f2e76291e3e6953d950709617c57a76bbeaa
URL: http://cgit.haiku-os.org/haiku/commit/?id=de26f2e
Author: Julian Harnath <julian.harnath@xxxxxxxxxxxxxx>
Date: Sun Mar 2 15:23:42 2014 UTC
Make code a bit easier to read, add some comments
* No functional change intended
----------------------------------------------------------------------------
diff --git a/src/add-ons/accelerants/radeon_hd/pll.cpp
b/src/add-ons/accelerants/radeon_hd/pll.cpp
index ce46b6d..bc963b8 100644
--- a/src/add-ons/accelerants/radeon_hd/pll.cpp
+++ b/src/add-ons/accelerants/radeon_hd/pll.cpp
@@ -45,6 +45,28 @@ extern "C" void _sPrintf(const char* format, ...);
// AtomBIOS: 16200 * 10 Khz 0.162 * 10 Ghz
+/* The PLL allows to synthesize a clock signal with a range of frequencies
+ * based on a single input reference clock signal. It uses several dividers
+ * to create a rational factor multiple of the input frequency.
+ *
+ * The reference clock signal frequency is pll_info::referenceFreq (in kHz ?
TODO).
+ * It is then, one after another...
+ * (1) divided by the (integer) reference divider (pll_info::referenceDiv).
+ * (2) multiplied by the fractional feedback divider, which sits in the
+ * PLL's feedback loop and thus multiplies the frequency. It allows
+ * using a rational number factor of the form "x.y", with
+ * x = pll_info::feedbackDiv and y = pll_info::feedbackDivFrac.
+ * (3) divided by the (integer) post divider (pll_info::postDiv).
+ * Allowed ranges are given in the pll_info min/max values.
+ *
+ * The resulting output pixel clock frequency is then:
+ *
+ * feedbackDiv + (feedbackDivFrac/10)
+ * f_out = referenceFreq * ------------------------------------
+ * referenceDiv * postDiv
+ */
+
+
status_t
pll_limit_probe(pll_info* pll)
{
@@ -342,16 +364,20 @@ pll_compute_post_divider(pll_info* pll)
}
+/*! Compute values for the fractional feedback divider to match the desired
+ * pixel clock frequency as closely as possible. Reference and post divider
+ * values are already filled in (if used).
+ */
status_t
pll_compute(pll_info* pll)
{
pll_compute_post_divider(pll);
- uint32 targetClock = pll->adjustedClock;
+ const uint32 targetClock = pll->adjustedClock;
pll->feedbackDiv = 0;
pll->feedbackDivFrac = 0;
- uint32 referenceFrequency = pll->referenceFreq;
+ const uint32 referenceFrequency = pll->referenceFreq;
if ((pll->flags & PLL_USE_REF_DIV) != 0) {
TRACE("%s: using AtomBIOS reference divider\n", __func__);
@@ -363,19 +389,21 @@ pll_compute(pll_info* pll)
if ((pll->flags & PLL_USE_FRAC_FB_DIV) != 0) {
TRACE("%s: using AtomBIOS fractional feedback divider\n",
__func__);
- uint32 tmp = pll->postDiv * pll->referenceDiv;
- tmp *= targetClock;
- pll->feedbackDiv = tmp / pll->referenceFreq;
- pll->feedbackDivFrac = tmp % pll->referenceFreq;
+ const uint32 numerator = pll->postDiv * pll->referenceDiv
+ * targetClock;
+ pll->feedbackDiv = numerator / referenceFrequency;
+ pll->feedbackDivFrac = numerator % referenceFrequency;
if (pll->feedbackDiv > pll->maxFeedbackDiv)
pll->feedbackDiv = pll->maxFeedbackDiv;
else if (pll->feedbackDiv < pll->minFeedbackDiv)
pll->feedbackDiv = pll->minFeedbackDiv;
+ // Put first 2 digits after the decimal point into
feedbackDivFrac
pll->feedbackDivFrac
- = (100 * pll->feedbackDivFrac) / pll->referenceFreq;
-
+ = (100 * pll->feedbackDivFrac) / referenceFrequency;
+
+ // Now round it to one digit
if (pll->feedbackDivFrac >= 5) {
pll->feedbackDivFrac -= 5;
pll->feedbackDivFrac /= 10;
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- » [haiku-commits] haiku: hrev46957 - src/add-ons/accelerants/radeon_hd - julian . harnath
