Hi,
* Walter Wagner <walter.wagner@xxxxxxxxxx> [170209 00:40]:
> Dear Tony Lindgren,
>
> I hope I'm right here and You are responsible for drivers/spi/spi-omap2-mcspi.c too.
Well I don't know much about the spi-omap2-mcspi.c driver.. But as
Franklin, Peter and Micheal have been patching it, they might have a
better idea what's going on. I've added them to Cc.
> To the history:
>
> We use TI AM33xx/AM43xx SOCs, especially SPI interface under kernel 4.1.20.
> Testing a device with very low baudrate (1,5 KHz) I made following experience:
>
> 1. The last byte was not always sure received --> sometimes I got timeout
>
> 2. The telegrams we have contain < 160 bytes, but we need DMA mode and not PIO (because CPU load)
>
> Therefore I've changed the driver.
> I hope these changes help other developer.
>
> I've attached the patch and the files itself for simple comparing.
Please check Documentation/SubmittingPatches and CodingStyle etc,
also note that with git you can easily generate patches :)
I've attached your diff below for easier reading.
Regards,
Tony
8< --------------------
--- a/drivers/spi/spi-omap2-mcspi.c 2016-03-17 19:11:03.000000000 +0100
+++ b/drivers/spi/spi-omap2-mcspi.c 2017-02-06 10:35:02.518061500 +0100
@@ -116,6 +116,11 @@
*/
#define DMA_MIN_BYTES 160
+/* Default value of delay at waiting for a bit in a register.
+ * Needed to avoid latency at waiting.
+ */
+#define BUSY_WAIT_DELAY 1 /* in ms */
+
/*
* Used for context save and restore, structure members to be updated whenever
@@ -138,6 +143,8 @@
struct omap2_mcspi_regs ctx;
int fifo_depth;
unsigned int pin_dir:1;
+ unsigned long dma_min_bytes;
+ unsigned long busy_wait_delay;
};
struct omap2_mcspi_cs {
@@ -363,6 +370,23 @@
return 0;
}
+static int mcspi_wait_for_reg_bit_interruptible(void __iomem *reg, unsigned long bit, unsigned long delay)
+{
+ unsigned long timeout;
+
+ timeout = jiffies + msecs_to_jiffies(1000);
+ while (!(readl_relaxed(reg) & bit)) {
+ if (time_after(jiffies, timeout)) {
+ if (!(readl_relaxed(reg) & bit))
+ return -ETIMEDOUT;
+ else
+ return 0;
+ }
+ msleep_interruptible(delay);
+ }
+ return 0;
+}
+
static void omap2_mcspi_rx_callback(void *data)
{
struct spi_device *spi = data;
@@ -496,8 +520,9 @@
if (l & OMAP2_MCSPI_CHCONF_TURBO) {
elements--;
- if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0)
- & OMAP2_MCSPI_CHSTAT_RXS)) {
+ if (mcspi_wait_for_reg_bit_interruptible(cs->base + OMAP2_MCSPI_CHSTAT0,
+ OMAP2_MCSPI_CHSTAT_RXS, mcspi->busy_wait_delay) == 0) {
+ /* reading completed */
u32 w;
w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0);
@@ -508,6 +533,7 @@
else /* word_len <= 32 */
((u32 *)xfer->rx_buf)[elements++] = w;
} else {
+ /* timeout */
int bytes_per_word = mcspi_bytes_per_word(word_len);
dev_err(&spi->dev, "DMA RX penultimate word empty\n");
count -= (bytes_per_word << 1);
@@ -515,8 +541,9 @@
return count;
}
}
- if (likely(mcspi_read_cs_reg(spi, OMAP2_MCSPI_CHSTAT0)
- & OMAP2_MCSPI_CHSTAT_RXS)) {
+ if (mcspi_wait_for_reg_bit_interruptible(cs->base + OMAP2_MCSPI_CHSTAT0,
+ OMAP2_MCSPI_CHSTAT_RXS, mcspi->busy_wait_delay) == 0) {
+ /* reading completed */
u32 w;
w = mcspi_read_cs_reg(spi, OMAP2_MCSPI_RX0);
@@ -527,6 +554,7 @@
else /* word_len <= 32 */
((u32 *)xfer->rx_buf)[elements] = w;
} else {
+ /* timeout */
dev_err(&spi->dev, "DMA RX last word empty\n");
count -= mcspi_bytes_per_word(word_len);
}
@@ -1141,7 +1169,7 @@
unsigned count;
if ((mcspi_dma->dma_rx && mcspi_dma->dma_tx) &&
- (m->is_dma_mapped || t->len >= DMA_MIN_BYTES))
+ (m->is_dma_mapped || t->len >= mcspi->dma_min_bytes))
omap2_mcspi_set_fifo(spi, t, 1);
omap2_mcspi_set_enable(spi, 1);
@@ -1152,7 +1180,7 @@
+ OMAP2_MCSPI_TX0);
if ((mcspi_dma->dma_rx && mcspi_dma->dma_tx) &&
- (m->is_dma_mapped || t->len >= DMA_MIN_BYTES))
+ (m->is_dma_mapped || t->len >= mcspi->dma_min_bytes))
count = omap2_mcspi_txrx_dma(spi, t);
else
count = omap2_mcspi_txrx_pio(spi, t);
@@ -1234,7 +1262,7 @@
goto out;
}
- if (m->is_dma_mapped || len < DMA_MIN_BYTES)
+ if (m->is_dma_mapped || len < mcspi->dma_min_bytes)
continue;
if (mcspi_dma->dma_tx && tx_buf != NULL) {
@@ -1375,6 +1403,11 @@
master->bus_num = pdev->id;
mcspi->pin_dir = pdata->pin_dir;
}
+ mcspi->dma_min_bytes = DMA_MIN_BYTES; /* default value */
+ of_property_read_u32(node, "ti,dma-min-bytes", &mcspi->dma_min_bytes);
+ mcspi->busy_wait_delay = BUSY_WAIT_DELAY; /* default value */
+ of_property_read_u32(node, "ti,busy-wait-delay", &mcspi->busy_wait_delay);
+
regs_offset = pdata->regs_offset;
r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
