[PATCH 6.0 0765/1073] dmaengine: apple-admac: Allocate cache SRAM to channels

Greg Kroah-Hartman
2022-12-28T16:29:49Z

From: Martin Povišer <povik+lin@cutebit.org>

[ Upstream commit 568aa6dd641f63166bb60d769e256789b3ac42d4 ]

There's a previously unknown part of the controller interface: We have
to assign SRAM carveouts to channels to store their in-flight samples
in. So, obtain the size of the SRAM from a read-only register and divide
it into 2K blocks for allocation to channels. The FIFO depths we
configure will always fit into 2K.

(This fixes audio artifacts during simultaneous playback/capture on
multiple channels -- which looking back is fully accounted for by having
had the caches in the DMA controller overlap in memory.)

Fixes: b127315d9a78 ("dmaengine: apple-admac: Add Apple ADMAC driver")
Signed-off-by: Martin Povišer <povik+lin@cutebit.org>
Link: https://lore.kernel.org/r/20221019132324.8585-2-povik+lin@cutebit.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dma/apple-admac.c | 102 +++++++++++++++++++++++++++++++++++++-
1 file changed, 101 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/apple-admac.c b/drivers/dma/apple-admac.c
index d69ed9c93648..e3334762be85 100644
--- a/drivers/dma/apple-admac.c
+++ b/drivers/dma/apple-admac.c
@@ -20,6 +20,12 @@
#define NCHANNELS_MAX 64
#define IRQ_NOUTPUTS 4

+/*
+ * For allocation purposes we split the cache
+ * memory into blocks of fixed size (given in bytes).
+ */
+#define SRAM_BLOCK 2048
+
#define RING_WRITE_SLOT GENMASK(1, 0)
#define RING_READ_SLOT GENMASK(5, 4)
#define RING_FULL BIT(9)
@@ -35,6 +41,9 @@
#define REG_TX_STOP 0x0004
#define REG_RX_START 0x0008
#define REG_RX_STOP 0x000c
+#define REG_IMPRINT 0x0090
+#define REG_TX_SRAM_SIZE 0x0094
+#define REG_RX_SRAM_SIZE 0x0098

#define REG_CHAN_CTL(ch) (0x8000 + (ch) * 0x200)
#define REG_CHAN_CTL_RST_RINGS BIT(0)
@@ -52,7 +61,9 @@
#define BUS_WIDTH_FRAME_2_WORDS 0x10
#define BUS_WIDTH_FRAME_4_WORDS 0x20

-#define CHAN_BUFSIZE 0x8000
+#define REG_CHAN_SRAM_CARVEOUT(ch) (0x8050 + (ch) * 0x200)
+#define CHAN_SRAM_CARVEOUT_SIZE GENMASK(31, 16)
+#define CHAN_SRAM_CARVEOUT_BASE GENMASK(15, 0)

#define REG_CHAN_FIFOCTL(ch) (0x8054 + (ch) * 0x200)
#define CHAN_FIFOCTL_LIMIT GENMASK(31, 16)
@@ -75,6 +86,8 @@ struct admac_chan {
struct dma_chan chan;
struct tasklet_struct tasklet;

+ u32 carveout;
+
spinlock_t lock;
struct admac_tx *current_tx;
int nperiod_acks;
@@ -91,11 +104,23 @@ struct admac_chan {
struct list_head to_free;
};

+struct admac_sram {
+ u32 size;
+ /*
+ * SRAM_CARVEOUT has 16-bit fields, so the SRAM cannot be larger than
+ * 64K and a 32-bit bitfield over 2K blocks covers it.
+ */
+ u32 allocated;
+};
+
struct admac_data {
struct dma_device dma;
struct device *dev;
__iomem void *base;

+ struct mutex cache_alloc_lock;
+ struct admac_sram txcache, rxcache;
+
int irq;
int irq_index;
int nchannels;
@@ -116,6 +141,60 @@ struct admac_tx {
struct list_head node;
};

+static int admac_alloc_sram_carveout(struct admac_data *ad,
+ enum dma_transfer_direction dir,
+ u32 *out)
+{
+ struct admac_sram *sram;
+ int i, ret = 0, nblocks;
+
+ if (dir == DMA_MEM_TO_DEV)
+ sram = &ad->txcache;
+ else
+ sram = &ad->rxcache;
+
+ mutex_lock(&ad->cache_alloc_lock);
+
+ nblocks = sram->size / SRAM_BLOCK;
+ for (i = 0; i < nblocks; i++)
+ if (!(sram->allocated & BIT(i)))
+ break;
+
+ if (i < nblocks) {
+ *out = FIELD_PREP(CHAN_SRAM_CARVEOUT_BASE, i * SRAM_BLOCK) |
+ FIELD_PREP(CHAN_SRAM_CARVEOUT_SIZE, SRAM_BLOCK);
+ sram->allocated |= BIT(i);
+ } else {
+ ret = -EBUSY;
+ }
+
+ mutex_unlock(&ad->cache_alloc_lock);
+
+ return ret;
+}
+
+static void admac_free_sram_carveout(struct admac_data *ad,
+ enum dma_transfer_direction dir,
+ u32 carveout)
+{
+ struct admac_sram *sram;
+ u32 base = FIELD_GET(CHAN_SRAM_CARVEOUT_BASE, carveout);
+ int i;
+
+ if (dir == DMA_MEM_TO_DEV)
+ sram = &ad->txcache;
+ else
+ sram = &ad->rxcache;
+
+ if (WARN_ON(base >= sram->size))
+ return;
+
+ mutex_lock(&ad->cache_alloc_lock);
+ i = base / SRAM_BLOCK;
+ sram->allocated &= ~BIT(i);
+ mutex_unlock(&ad->cache_alloc_lock);
+}
+
static void admac_modify(struct admac_data *ad, int reg, u32 mask, u32 val)
{
void __iomem *addr = ad->base + reg;
@@ -464,15 +543,28 @@ static void admac_synchronize(struct dma_chan *chan)
static int admac_alloc_chan_resources(struct dma_chan *chan)
{
struct admac_chan *adchan = to_admac_chan(chan);
+ struct admac_data *ad = adchan->host;
+ int ret;

dma_cookie_init(&adchan->chan);
+ ret = admac_alloc_sram_carveout(ad, admac_chan_direction(adchan->no),
+ &adchan->carveout);
+ if (ret < 0)
+ return ret;
+
+ writel_relaxed(adchan->carveout,
+ ad->base + REG_CHAN_SRAM_CARVEOUT(adchan->no));
return 0;
}

static void admac_free_chan_resources(struct dma_chan *chan)
{
+ struct admac_chan *adchan = to_admac_chan(chan);
+
admac_terminate_all(chan);
admac_synchronize(chan);
+ admac_free_sram_carveout(adchan->host, admac_chan_direction(adchan->no),
+ adchan->carveout);
}

static struct dma_chan *admac_dma_of_xlate(struct of_phandle_args *dma_spec,
@@ -710,6 +802,7 @@ static int admac_probe(struct platform_device *pdev)
platform_set_drvdata(pdev, ad);
ad->dev = &pdev->dev;
ad->nchannels = nchannels;
+ mutex_init(&ad->cache_alloc_lock);

/*
* The controller has 4 IRQ outputs. Try them all until
@@ -788,6 +881,13 @@ static int admac_probe(struct platform_device *pdev)
goto free_irq;
}

+ ad->txcache.size = readl_relaxed(ad->base + REG_TX_SRAM_SIZE);
+ ad->rxcache.size = readl_relaxed(ad->base + REG_RX_SRAM_SIZE);
+
+ dev_info(&pdev->dev, "Audio DMA Controller\n");
+ dev_info(&pdev->dev, "imprint %x TX cache %u RX cache %u\n",
+ readl_relaxed(ad->base + REG_IMPRINT), ad->txcache.size, ad->rxcache.size);
+
return 0;

free_irq:
--
2.35.1