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authorPierre Ossman <pierre@ossman.eu>2013-11-06 20:09:08 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-08 07:29:28 -0800
commitf789de214b88dd2f5bbb372625b2e284f8469c4b (patch)
tree8bafb15d90d17694a38623d6c318f04edc470ef2
parent9baca2ff1035fbdc7f910a4b6fb34d4bec3f443b (diff)
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drm/radeon/audio: improve ACR calculation
commit a2098250fbda149cfad9e626afe80abe3b21e574 upstream. In order to have any realistic chance of calculating proper ACR values, we need to be able to calculate both N and CTS, not just CTS. We still aim for the ideal N as specified in the HDMI spec though. bug: https://bugs.freedesktop.org/show_bug.cgi?id=69675 Signed-off-by: Pierre Ossman <pierre@ossman.eu> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> Cc: Josh Boyer <jwboyer@fedoraproject.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/gpu/drm/radeon/r600_hdmi.c68
1 files changed, 46 insertions, 22 deletions
diff --git a/drivers/gpu/drm/radeon/r600_hdmi.c b/drivers/gpu/drm/radeon/r600_hdmi.c
index 635e8f2e84f..cf4c1009039 100644
--- a/drivers/gpu/drm/radeon/r600_hdmi.c
+++ b/drivers/gpu/drm/radeon/r600_hdmi.c
@@ -24,6 +24,7 @@
* Authors: Christian K├Ânig
*/
#include <linux/hdmi.h>
+#include <linux/gcd.h>
#include <drm/drmP.h>
#include <drm/radeon_drm.h>
#include "radeon.h"
@@ -67,25 +68,47 @@ static const struct radeon_hdmi_acr r600_hdmi_predefined_acr[] = {
{ 74250, 4096, 74250, 6272, 82500, 6144, 74250 }, /* 74.25 MHz */
{ 148352, 11648, 421875, 8918, 234375, 5824, 140625 }, /* 148.50/1.001 MHz */
{ 148500, 4096, 148500, 6272, 165000, 6144, 148500 }, /* 148.50 MHz */
- { 0, 4096, 0, 6272, 0, 6144, 0 } /* Other */
};
+
/*
- * calculate CTS value if it's not found in the table
+ * calculate CTS and N values if they are not found in the table
*/
-static void r600_hdmi_calc_cts(uint32_t clock, int *CTS, int N, int freq)
+static void r600_hdmi_calc_cts(uint32_t clock, int *CTS, int *N, int freq)
{
- u64 n;
- u32 d;
-
- if (*CTS == 0) {
- n = (u64)clock * (u64)N * 1000ULL;
- d = 128 * freq;
- do_div(n, d);
- *CTS = n;
- }
- DRM_DEBUG("Using ACR timing N=%d CTS=%d for frequency %d\n",
- N, *CTS, freq);
+ int n, cts;
+ unsigned long div, mul;
+
+ /* Safe, but overly large values */
+ n = 128 * freq;
+ cts = clock * 1000;
+
+ /* Smallest valid fraction */
+ div = gcd(n, cts);
+
+ n /= div;
+ cts /= div;
+
+ /*
+ * The optimal N is 128*freq/1000. Calculate the closest larger
+ * value that doesn't truncate any bits.
+ */
+ mul = ((128*freq/1000) + (n-1))/n;
+
+ n *= mul;
+ cts *= mul;
+
+ /* Check that we are in spec (not always possible) */
+ if (n < (128*freq/1500))
+ printk(KERN_WARNING "Calculated ACR N value is too small. You may experience audio problems.\n");
+ if (n > (128*freq/300))
+ printk(KERN_WARNING "Calculated ACR N value is too large. You may experience audio problems.\n");
+
+ *N = n;
+ *CTS = cts;
+
+ DRM_DEBUG("Calculated ACR timing N=%d CTS=%d for frequency %d\n",
+ *N, *CTS, freq);
}
struct radeon_hdmi_acr r600_hdmi_acr(uint32_t clock)
@@ -93,15 +116,16 @@ struct radeon_hdmi_acr r600_hdmi_acr(uint32_t clock)
struct radeon_hdmi_acr res;
u8 i;
- for (i = 0; r600_hdmi_predefined_acr[i].clock != clock &&
- r600_hdmi_predefined_acr[i].clock != 0; i++)
- ;
- res = r600_hdmi_predefined_acr[i];
+ /* Precalculated values for common clocks */
+ for (i = 0; i < ARRAY_SIZE(r600_hdmi_predefined_acr); i++) {
+ if (r600_hdmi_predefined_acr[i].clock == clock)
+ return r600_hdmi_predefined_acr[i];
+ }
- /* In case some CTS are missing */
- r600_hdmi_calc_cts(clock, &res.cts_32khz, res.n_32khz, 32000);
- r600_hdmi_calc_cts(clock, &res.cts_44_1khz, res.n_44_1khz, 44100);
- r600_hdmi_calc_cts(clock, &res.cts_48khz, res.n_48khz, 48000);
+ /* And odd clocks get manually calculated */
+ r600_hdmi_calc_cts(clock, &res.cts_32khz, &res.n_32khz, 32000);
+ r600_hdmi_calc_cts(clock, &res.cts_44_1khz, &res.n_44_1khz, 44100);
+ r600_hdmi_calc_cts(clock, &res.cts_48khz, &res.n_48khz, 48000);
return res;
}