brcm2708: rename target to bcm27xx

This change makes the names of Broadcom targets consistent by using
the common notation based on SoC/CPU ID (which is used internally
anyway), bcmXXXX instead of brcmXXXX.
This is even used for target TITLE in make menuconfig already,
only the short target name used brcm so far.

Despite, since subtargets range from bcm2708 to bcm2711, it seems
appropriate to use bcm27xx instead of bcm2708 (again, as already done
for BOARDNAME).

This also renames the packages brcm2708-userland and brcm2708-gpu-fw.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>
Acked-by: Álvaro Fernández Rojas <noltari@gmail.com>

1 files changed, 82 insertions, 0 deletions

diff --git a/target/linux/bcm27xx/patches-4.19/950-0408-staging-bcm2835-audio-interpolate-audio-delay.patch b/target/linux/bcm27xx/patches-4.19/950-0408-staging-bcm2835-audio-interpolate-audio-delay.patch
new file mode 100644
index 0000000000..cf5f11c091
--- /dev/null
+++ b/target/linux/bcm27xx/patches-4.19/950-0408-staging-bcm2835-audio-interpolate-audio-delay.patch
@@ -0,0 +1,82 @@
+From 2ba82d9516203ce41f33e98adb667bedee3622bc Mon Sep 17 00:00:00 2001
+From: Mike Brady <mikebrady@eircom.net>
+Date: Mon, 22 Oct 2018 20:17:08 +0100
+Subject: [PATCH] staging: bcm2835-audio: interpolate audio delay
+
+commit a105a3a72824e0ac685a0711a67e4dbe29de62d0 upstream.
+
+When the BCM2835 audio output is used, userspace sees a jitter up to 10ms
+in the audio position, aka "delay" -- the number of frames that must
+be output before a new frame would be played.
+Make this a bit nicer for userspace by interpolating the position
+using the CPU clock.
+The overhead is small -- an extra ktime_get() every time a GPU message
+is sent -- and another call and a few calculations whenever the delay
+is sought from userland.
+At 48,000 frames per second, i.e. approximately 20 microseconds per
+frame, it would take a clock inaccuracy of
+20 microseconds in 10 milliseconds -- 2,000 parts per million --
+to result in an inaccurate estimate, whereas
+crystal- or resonator-based clocks typically have an
+inaccuracy of 10s to 100s of parts per million.
+
+Signed-off-by: Mike Brady <mikebrady@eircom.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ .../vc04_services/bcm2835-audio/bcm2835-pcm.c | 20 +++++++++++++++++++
+ .../vc04_services/bcm2835-audio/bcm2835.h     |  1 +
+ 2 files changed, 21 insertions(+)
+
+--- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
++++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835-pcm.c
+@@ -74,6 +74,7 @@ void bcm2835_playback_fifo(struct bcm283
+ 	atomic_set(&alsa_stream->pos, pos);
+ 
+ 	alsa_stream->period_offset += bytes;
++	alsa_stream->interpolate_start = ktime_get();
+ 	if (alsa_stream->period_offset >= alsa_stream->period_size) {
+ 		alsa_stream->period_offset %= alsa_stream->period_size;
+ 		snd_pcm_period_elapsed(substream);
+@@ -237,6 +238,7 @@ static int snd_bcm2835_pcm_prepare(struc
+ 	atomic_set(&alsa_stream->pos, 0);
+ 	alsa_stream->period_offset = 0;
+ 	alsa_stream->draining = false;
++	alsa_stream->interpolate_start = ktime_get();
+ 
+ 	return 0;
+ }
+@@ -286,6 +288,24 @@ snd_bcm2835_pcm_pointer(struct snd_pcm_s
+ {
+ 	struct snd_pcm_runtime *runtime = substream->runtime;
+ 	struct bcm2835_alsa_stream *alsa_stream = runtime->private_data;
++	ktime_t now = ktime_get();
++
++	/* Give userspace better delay reporting by interpolating between GPU
++	 * notifications, assuming audio speed is close enough to the clock
++	 * used for ktime
++	 */
++
++	if ((ktime_to_ns(alsa_stream->interpolate_start)) &&
++	    (ktime_compare(alsa_stream->interpolate_start, now) < 0)) {
++		u64 interval =
++			(ktime_to_ns(ktime_sub(now,
++				alsa_stream->interpolate_start)));
++		u64 frames_output_in_interval =
++			div_u64((interval * runtime->rate), 1000000000);
++		snd_pcm_sframes_t frames_output_in_interval_sized =
++			-frames_output_in_interval;
++		runtime->delay = frames_output_in_interval_sized;
++	}
+ 
+ 	return snd_pcm_indirect_playback_pointer(substream,
+ 		&alsa_stream->pcm_indirect,
+--- a/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h
++++ b/drivers/staging/vc04_services/bcm2835-audio/bcm2835.h
+@@ -78,6 +78,7 @@ struct bcm2835_alsa_stream {
+ 	unsigned int period_offset;
+ 	unsigned int buffer_size;
+ 	unsigned int period_size;
++	ktime_t interpolate_start;
+ 
+ 	struct bcm2835_audio_instance *instance;
+ 	int idx;