[media] tw686x: audio: Allow to configure the period size

Currently, the driver has a fixed period size of 4096 bytes
(2048 frames). Since this hardware can configure the audio
capture size, this commit allows a period size range of [512-4096].

This is very useful to reduce the audio latency.

Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

diff --git a/drivers/media/pci/tw686x/tw686x-audio.c b/drivers/media/pci/tw686x/tw686x-audio.c
index a14d1b0..987a226 100644 (file)
--- a/drivers/media/pci/tw686x/tw686x-audio.c
+++ b/drivers/media/pci/tw686x/tw686x-audio.c
@@ -71,7 +71,7 @@ void tw686x_audio_irq(struct tw686x_dev *dev, unsigned long requests,
                desc = &ac->dma_descs[pb];
                if (desc->virt) {
                        memcpy(done->virt, desc->virt,
-                              desc->size);
+                              dev->period_size);
                } else {
                        u32 reg = pb ? ADMA_B_ADDR[ch] : ADMA_P_ADDR[ch];
                        reg_write(dev, reg, next->dma);
@@ -93,10 +93,11 @@ static int tw686x_pcm_hw_free(struct snd_pcm_substream *ss)
 }
 
 /*
- * The audio device rate is global and shared among all
+ * Audio parameters are global and shared among all
  * capture channels. The driver makes no effort to prevent
- * rate modifications. User is free change the rate, but it
- * means changing the rate for all capture sub-devices.
+ * any modifications. User is free change the audio rate,
+ * or period size, thus changing parameters for all capture
+ * sub-devices.
  */
 static const struct snd_pcm_hardware tw686x_capture_hw = {
        .info                   = (SNDRV_PCM_INFO_MMAP |
@@ -109,9 +110,9 @@ static const struct snd_pcm_hardware tw686x_capture_hw = {
        .rate_max               = 48000,
        .channels_min           = 1,
        .channels_max           = 1,
-       .buffer_bytes_max       = TW686X_AUDIO_PAGE_MAX * TW686X_AUDIO_PAGE_SZ,
-       .period_bytes_min       = TW686X_AUDIO_PAGE_SZ,
-       .period_bytes_max       = TW686X_AUDIO_PAGE_SZ,
+       .buffer_bytes_max       = TW686X_AUDIO_PAGE_MAX * AUDIO_DMA_SIZE_MAX,
+       .period_bytes_min       = AUDIO_DMA_SIZE_MIN,
+       .period_bytes_max       = AUDIO_DMA_SIZE_MAX,
        .periods_min            = TW686X_AUDIO_PERIODS_MIN,
        .periods_max            = TW686X_AUDIO_PERIODS_MAX,
 };
@@ -166,12 +167,21 @@ static int tw686x_pcm_prepare(struct snd_pcm_substream *ss)
                reg_write(dev, AUDIO_CONTROL2, reg);
        }
 
-       if (period_size != TW686X_AUDIO_PAGE_SZ ||
-           rt->periods < TW686X_AUDIO_PERIODS_MIN ||
-           rt->periods > TW686X_AUDIO_PERIODS_MAX) {
-               return -EINVAL;
+       if (dev->period_size != period_size) {
+               u32 reg;
+
+               dev->period_size = period_size;
+               reg = reg_read(dev, AUDIO_CONTROL1);
+               reg &= ~(AUDIO_DMA_SIZE_MASK << AUDIO_DMA_SIZE_SHIFT);
+               reg |= period_size << AUDIO_DMA_SIZE_SHIFT;
+
+               reg_write(dev, AUDIO_CONTROL1, reg);
        }
 
+       if (rt->periods < TW686X_AUDIO_PERIODS_MIN ||
+           rt->periods > TW686X_AUDIO_PERIODS_MAX)
+               return -EINVAL;
+
        spin_lock_irqsave(&ac->lock, flags);
        INIT_LIST_HEAD(&ac->buf_list);
 
@@ -282,8 +292,8 @@ static int tw686x_snd_pcm_init(struct tw686x_dev *dev)
        return snd_pcm_lib_preallocate_pages_for_all(pcm,
                                SNDRV_DMA_TYPE_DEV,
                                snd_dma_pci_data(dev->pci_dev),
-                               TW686X_AUDIO_PAGE_MAX * TW686X_AUDIO_PAGE_SZ,
-                               TW686X_AUDIO_PAGE_MAX * TW686X_AUDIO_PAGE_SZ);
+                               TW686X_AUDIO_PAGE_MAX * AUDIO_DMA_SIZE_MAX,
+                               TW686X_AUDIO_PAGE_MAX * AUDIO_DMA_SIZE_MAX);
 }
 
 static void tw686x_audio_dma_free(struct tw686x_dev *dev,
@@ -318,7 +328,7 @@ static int tw686x_audio_dma_alloc(struct tw686x_dev *dev,
                u32 reg = pb ? ADMA_B_ADDR[ac->ch] : ADMA_P_ADDR[ac->ch];
                void *virt;
 
-               virt = pci_alloc_consistent(dev->pci_dev, TW686X_AUDIO_PAGE_SZ,
+               virt = pci_alloc_consistent(dev->pci_dev, AUDIO_DMA_SIZE_MAX,
                                            &ac->dma_descs[pb].phys);
                if (!virt) {
                        dev_err(&dev->pci_dev->dev,
@@ -327,7 +337,7 @@ static int tw686x_audio_dma_alloc(struct tw686x_dev *dev,
                        return -ENOMEM;
                }
                ac->dma_descs[pb].virt = virt;
-               ac->dma_descs[pb].size = TW686X_AUDIO_PAGE_SZ;
+               ac->dma_descs[pb].size = AUDIO_DMA_SIZE_MAX;
                reg_write(dev, reg, ac->dma_descs[pb].phys);
        }
        return 0;
@@ -358,12 +368,8 @@ int tw686x_audio_init(struct tw686x_dev *dev)
        struct snd_card *card;
        int err, ch;
 
-       /*
-        * AUDIO_CONTROL1
-        * DMA byte length [31:19] = 4096 (i.e. ALSA period)
-        * External audio enable [0] = enabled
-        */
-       reg_write(dev, AUDIO_CONTROL1, 0x80000001);
+       /* Enable external audio */
+       reg_write(dev, AUDIO_CONTROL1, BIT(0));
 
        err = snd_card_new(&pci_dev->dev, SNDRV_DEFAULT_IDX1,
                           SNDRV_DEFAULT_STR1,

diff --git a/drivers/media/pci/tw686x/tw686x-regs.h b/drivers/media/pci/tw686x/tw686x-regs.h
index 37c39bc..15a9566 100644 (file)
--- a/drivers/media/pci/tw686x/tw686x-regs.h
+++ b/drivers/media/pci/tw686x/tw686x-regs.h
@@ -105,6 +105,10 @@
                                                  0x2d0, 0x2d1, 0x2d2, 0x2d3 })
 
 #define SYS_MODE_DMA_SHIFT     13
+#define AUDIO_DMA_SIZE_SHIFT   19
+#define AUDIO_DMA_SIZE_MIN     SZ_512
+#define AUDIO_DMA_SIZE_MAX     SZ_4K
+#define AUDIO_DMA_SIZE_MASK    (SZ_8K - 1)
 
 #define DMA_CMD_ENABLE         BIT(31)
 #define INT_STATUS_DMA_TOUT    BIT(17)

diff --git a/drivers/media/pci/tw686x/tw686x.h b/drivers/media/pci/tw686x/tw686x.h
index 25e3c84..4acb905 100644 (file)
--- a/drivers/media/pci/tw686x/tw686x.h
+++ b/drivers/media/pci/tw686x/tw686x.h
@@ -27,7 +27,6 @@
 #define TYPE_SECOND_GEN                0x10
 #define TW686X_DEF_PHASE_REF   0x1518
 
-#define TW686X_AUDIO_PAGE_SZ           4096
 #define TW686X_AUDIO_PAGE_MAX          16
 #define TW686X_AUDIO_PERIODS_MIN       2
 #define TW686X_AUDIO_PERIODS_MAX       TW686X_AUDIO_PAGE_MAX
@@ -139,7 +138,9 @@ struct tw686x_dev {
        struct tw686x_video_channel *video_channels;
        struct tw686x_audio_channel *audio_channels;
 
-       int audio_rate; /* per-device value */
+       /* Per-device audio parameters */
+       int audio_rate;
+       int period_size;
 
        struct timer_list dma_delay_timer;
        u32 pending_dma_en; /* must be protected by lock */