Re: [PATCH v3 3/7] spi: imx: add support for all SPI word width for DMA transfer

From: Anton Bondarenko
Date: Sat Nov 14 2015 - 05:08:32 EST



On 01.11.2015 15:41, Anton Bondarenko wrote:
From: Anton Bondarenko <anton_bondarenko@xxxxxxxxxx>

DMA transfer for SPI was limited to up to 8 bits word size until now.
Sync in SPI burst size and DMA bus width is necessary to correctly
support other BPW supported by HW.

Signed-off-by: Anton Bondarenko <anton_bondarenko@xxxxxxxxxx>
---
drivers/spi/spi-imx.c | 133 ++++++++++++++++++++++++++++++++++++++------------
1 file changed, 102 insertions(+), 31 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 9b80c7f..06f52c3 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -89,11 +89,15 @@ struct spi_imx_data {

struct completion xfer_done;
void __iomem *base;
+ unsigned long base_phys;
+
struct clk *clk_per;
struct clk *clk_ipg;
unsigned long spi_clk;
unsigned int spi_bus_clk;

+ unsigned int bytes_per_word;
+
unsigned int count;
void (*tx)(struct spi_imx_data *);
void (*rx)(struct spi_imx_data *);
@@ -195,12 +199,31 @@ static unsigned int spi_imx_clkdiv_2(unsigned int fin,
return 7;
}

+static int spi_imx_get_bytes_per_word(const int bpw)
+{
+ return DIV_ROUND_UP(bpw, BITS_PER_BYTE);
+}
+
static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
struct spi_transfer *transfer)
{
struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
+ unsigned int bpw = transfer->bits_per_word;
+
+ if (!bpw)
+ bpw = spi->bits_per_word;

- if (spi_imx->dma_is_inited && transfer->len > spi_imx->wml)
+ bpw = spi_imx_get_bytes_per_word(bpw);
+
+ /*
+ * We need to use SPI word size in calculation to decide
+ * if we want to go with DMA or PIO mode. Just a short example:
+ * We need to transfer 24 SPI words with BPW == 32. This will take
+ * 24 PIO writes to FIFO (and same for reads). But transfer->len will
+ * be 24*4=96 bytes. WML is 32 SPI words. The decision will be incorrect
+ * if we do not take into account SPI bits per word.
+ */
+ if (spi_imx->dma_is_inited && (transfer->len > spi_imx->wml * bpw))
return true;
return false;
}
@@ -764,11 +787,60 @@ static irqreturn_t spi_imx_isr(int irq, void *dev_id)
return IRQ_HANDLED;
}

+static int spi_imx_sdma_configure(struct spi_master *master)
+{
+ int ret;
+ enum dma_slave_buswidth dsb_default = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ struct dma_slave_config slave_config = {};
+ struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
+
+ switch (spi_imx->bytes_per_word) {
+ case 4:
+ dsb_default = DMA_SLAVE_BUSWIDTH_4_BYTES;
+ break;
+ case 2:
+ dsb_default = DMA_SLAVE_BUSWIDTH_2_BYTES;
+ break;
+ case 1:
+ dsb_default = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ break;
+ default:
+ pr_err("Not supported word size %d\n", spi_imx->bytes_per_word);
+ ret = -EINVAL;
+ goto err;
+ }
+
+ slave_config.direction = DMA_MEM_TO_DEV;
+ slave_config.dst_addr = spi_imx->base_phys + MXC_CSPITXDATA;
+ slave_config.dst_addr_width = dsb_default;
+ slave_config.dst_maxburst = spi_imx->wml;
+ ret = dmaengine_slave_config(master->dma_tx, &slave_config);
+ if (ret) {
+ pr_err("error in TX dma configuration.\n");
+ goto err;
+ }
+
+ memset(&slave_config, 0, sizeof(slave_config));
+
+ slave_config.direction = DMA_DEV_TO_MEM;
+ slave_config.src_addr = spi_imx->base_phys + MXC_CSPIRXDATA;
+ slave_config.src_addr_width = dsb_default;
+ slave_config.src_maxburst = spi_imx->wml;
+ ret = dmaengine_slave_config(master->dma_rx, &slave_config);
+ if (ret)
+ pr_err("error in RX dma configuration.\n");
+
+err:
+ return ret;
+}
+
static int spi_imx_setupxfer(struct spi_device *spi,
struct spi_transfer *t)
{
struct spi_imx_data *spi_imx = spi_master_get_devdata(spi->master);
struct spi_imx_config config;
+ unsigned int new_bytes_per_word;
+ int ret = 0;

config.bpw = t ? t->bits_per_word : spi->bits_per_word;
config.speed_hz = t ? t->speed_hz : spi->max_speed_hz;
@@ -792,9 +864,19 @@ static int spi_imx_setupxfer(struct spi_device *spi,
spi_imx->tx = spi_imx_buf_tx_u32;
}

- spi_imx->devtype_data->config(spi_imx, &config);
+ new_bytes_per_word = spi_imx_get_bytes_per_word(config.bpw);
+ if (spi_imx->dma_is_inited &&
+ spi_imx->bytes_per_word != new_bytes_per_word) {
+ spi_imx->bytes_per_word = new_bytes_per_word;
+ ret = spi_imx_sdma_configure(spi->master);
+ if (ret != 0)
+ pr_err("Can't configure SDMA, error %d\n", ret);
+ }
+
+ if (!ret)
+ ret = spi_imx->devtype_data->config(spi_imx, &config);

- return 0;
+ return ret;
}

static void spi_imx_sdma_exit(struct spi_imx_data *spi_imx)
@@ -815,10 +897,8 @@ static void spi_imx_sdma_exit(struct spi_imx_data *spi_imx)
}

static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
- struct spi_master *master,
- const struct resource *res)
+ struct spi_master *master)
{
- struct dma_slave_config slave_config = {};
int ret;

/* use pio mode for i.mx6dl chip TKT238285 */
@@ -835,16 +915,6 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
goto err;
}

- slave_config.direction = DMA_MEM_TO_DEV;
- slave_config.dst_addr = res->start + MXC_CSPITXDATA;
- slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
- slave_config.dst_maxburst = spi_imx->wml;
- ret = dmaengine_slave_config(master->dma_tx, &slave_config);
- if (ret) {
- dev_err(dev, "error in TX dma configuration.\n");
- goto err;
- }
-
/* Prepare for RX : */
master->dma_rx = dma_request_slave_channel(dev, "rx");
if (!master->dma_rx) {
@@ -853,22 +923,19 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
goto err;
}

- slave_config.direction = DMA_DEV_TO_MEM;
- slave_config.src_addr = res->start + MXC_CSPIRXDATA;
- slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
- slave_config.src_maxburst = spi_imx->wml;
- ret = dmaengine_slave_config(master->dma_rx, &slave_config);
- if (ret) {
- dev_err(dev, "error in RX dma configuration.\n");
- goto err;
- }
-
init_completion(&spi_imx->dma_rx_completion);
init_completion(&spi_imx->dma_tx_completion);
master->can_dma = spi_imx_can_dma;
master->max_dma_len = MAX_SDMA_BD_BYTES;
spi_imx->bitbang.master->flags = SPI_MASTER_MUST_RX |
SPI_MASTER_MUST_TX;
+ spi_imx->bytes_per_word = 1;
+ ret = spi_imx_sdma_configure(master);
+ if (ret) {
+ dev_info(dev, "cannot get setup DMA.\n");
+ goto err;
+ }
+
spi_imx->dma_is_inited = 1;

return 0;
@@ -925,7 +992,8 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
int ret;
unsigned long timeout;
unsigned long transfer_timeout;
- const int left = transfer->len % spi_imx->wml;
+ const int left = transfer->len %
+ (spi_imx->wml * spi_imx->bytes_per_word);
struct spi_master *master = spi_imx->bitbang.master;
struct sg_table *tx = &transfer->tx_sg, *rx = &transfer->rx_sg;

@@ -998,7 +1066,7 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
dmaengine_terminate_all(master->dma_rx);
} else {
transfer_timeout = spi_imx_calculate_timeout(spi_imx,
- spi_imx->wml);
+ spi_imx->bytes_per_word * spi_imx->wml);
timeout = wait_for_completion_timeout(
&spi_imx->dma_rx_completion, transfer_timeout);
if (!timeout) {
@@ -1016,7 +1084,9 @@ static int spi_imx_dma_transfer(struct spi_imx_data *spi_imx,
DMA_FROM_DEVICE);

spi_imx->rx_buf = pio_buffer;
- spi_imx->txfifo = left;
+ spi_imx->txfifo = DIV_ROUND_UP(left,
+ spi_imx->bytes_per_word);
+
reinit_completion(&spi_imx->xfer_done);

spi_imx->devtype_data->intctrl(spi_imx, MXC_INT_TCEN);
@@ -1224,6 +1294,7 @@ static int spi_imx_probe(struct platform_device *pdev)
ret = PTR_ERR(spi_imx->base);
goto out_master_put;
}
+ spi_imx->base_phys = res->start;

irq = platform_get_irq(pdev, 0);
if (irq < 0) {
@@ -1263,8 +1334,8 @@ static int spi_imx_probe(struct platform_device *pdev)
* Only validated on i.mx6 now, can remove the constrain if validated on
* other chips.
*/
- if (spi_imx->devtype_data == &imx51_ecspi_devtype_data
- && spi_imx_sdma_init(&pdev->dev, spi_imx, master, res))
+ if (spi_imx->devtype_data == &imx51_ecspi_devtype_data &&
+ spi_imx_sdma_init(&pdev->dev, spi_imx, master))
dev_err(&pdev->dev, "dma setup error,use pio instead\n");

spi_imx->devtype_data->reset(spi_imx);


Does anyone has other comments regarding this commit?

Regards, Anton
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