target/linux/bcm27xx/patches-5.4/950-0372-Pisound-MIDI-communication-fixes-for-scaled-down-CPU.patch

   1 From 67dd4d137557909279a21c1b5de87a24c84903f9 Mon Sep 17 00:00:00 2001
   2 From: Giedrius <giedrius@blokas.io>
   3 Date: Tue, 7 Jan 2020 11:04:21 +0200
   4 Subject: [PATCH] Pisound: MIDI communication fixes for scaled down
   5  CPU.
   6 MIME-Version: 1.0
   7 Content-Type: text/plain; charset=UTF-8
   8 Content-Transfer-Encoding: 8bit
   9
  10 * Increased maximum SPI communication speed to avoid running too slow
  11   when the CPU is scaled down and losing MIDI data.
  12
  13 * Keep track of buffer usage in millibytes for higher precision.
  14
  15 Signed-off-by: Giedrius Trainavičius <giedrius@blokas.io>
  16 ---
  17  sound/soc/bcm/pisound.c | 31 ++++++++++++++++++-------------
  18  1 file changed, 18 insertions(+), 13 deletions(-)
  19
  20 --- a/sound/soc/bcm/pisound.c
  21 +++ b/sound/soc/bcm/pisound.c
  22 @@ -1,6 +1,6 @@
  23  /*
  24   * Pisound Linux kernel module.
  25 - * Copyright (C) 2016-2019  Vilniaus Blokas UAB, https://blokas.io/pisound
  26 + * Copyright (C) 2016-2020  Vilniaus Blokas UAB, https://blokas.io/pisound
  27   *
  28   * This program is free software; you can redistribute it and/or
  29   * modify it under the terms of the GNU General Public License
  30 @@ -326,7 +326,7 @@ static void spi_transfer(const uint8_t *
  31         transfer.tx_buf = txbuf;
  32         transfer.rx_buf = rxbuf;
  33         transfer.len = len;
  34 -       transfer.speed_hz = 100000;
  35 +       transfer.speed_hz = 150000;
  36         transfer.delay_usecs = 10;
  37         spi_message_add_tail(&transfer, &msg);
  38
  39 @@ -403,9 +403,9 @@ static struct spi_device *pisnd_spi_find
  40  static void pisnd_work_handler(struct work_struct *work)
  41  {
  42         enum { TRANSFER_SIZE = 4 };
  43 -       enum { PISOUND_OUTPUT_BUFFER_SIZE = 128 };
  44 -       enum { MIDI_BYTES_PER_SECOND = 3125 };
  45 -       int out_buffer_used = 0;
  46 +       enum { PISOUND_OUTPUT_BUFFER_SIZE_MILLIBYTES = 127 * 1000 };
  47 +       enum { MIDI_MILLIBYTES_PER_JIFFIE = (3125 * 1000) / HZ };
  48 +       int out_buffer_used_millibytes = 0;
  49         unsigned long now;
  50         uint8_t val;
  51         uint8_t txbuf[TRANSFER_SIZE];
  52 @@ -445,7 +445,9 @@ static void pisnd_work_handler(struct wo
  53                         had_data = false;
  54                         memset(txbuf, 0, sizeof(txbuf));
  55                         for (i = 0; i < sizeof(txbuf) &&
  56 -                               out_buffer_used < PISOUND_OUTPUT_BUFFER_SIZE;
  57 +                               ((out_buffer_used_millibytes+1000 <
  58 +                               PISOUND_OUTPUT_BUFFER_SIZE_MILLIBYTES) ||
  59 +                               g_ledFlashDurationChanged);
  60                                 i += 2) {
  61
  62                                 val = 0;
  63 @@ -458,7 +460,7 @@ static void pisnd_work_handler(struct wo
  64                                 } else if (kfifo_get(&spi_fifo_out, &val)) {
  65                                         txbuf[i+0] = 0x0f;
  66                                         txbuf[i+1] = val;
  67 -                                       ++out_buffer_used;
  68 +                                       out_buffer_used_millibytes += 1000;
  69                                 }
  70                         }
  71
  72 @@ -469,12 +471,14 @@ static void pisnd_work_handler(struct wo
  73                          * rate.
  74                          */
  75                         now = jiffies;
  76 -                       out_buffer_used -=
  77 -                               (MIDI_BYTES_PER_SECOND / HZ) /
  78 -                               (now - last_transfer_at);
  79 -                       if (out_buffer_used < 0)
  80 -                               out_buffer_used = 0;
  81 -                       last_transfer_at = now;
  82 +                       if (now != last_transfer_at) {
  83 +                               out_buffer_used_millibytes -=
  84 +                                       (now - last_transfer_at) *
  85 +                                       MIDI_MILLIBYTES_PER_JIFFIE;
  86 +                               if (out_buffer_used_millibytes < 0)
  87 +                                       out_buffer_used_millibytes = 0;
  88 +                               last_transfer_at = now;
  89 +                       }
  90
  91                         for (i = 0; i < sizeof(rxbuf); i += 2) {
  92                                 if (rxbuf[i]) {
  93 @@ -489,6 +493,7 @@ static void pisnd_work_handler(struct wo
  94                         || !kfifo_is_empty(&spi_fifo_out)
  95                         || pisnd_spi_has_more()
  96                         || g_ledFlashDurationChanged
  97 +                       || out_buffer_used_millibytes != 0
  98                         );
  99
 100                 if (!kfifo_is_empty(&spi_fifo_in) && g_recvCallback)