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Date: Thu, 7 Nov 2013 10:34:06 +0100
From: Richard Genoud <richard.genoud@...il.com>
To: Nicolas Ferre <nicolas.ferre@...el.com>,
Mark Brown <broonie@...nel.org>
Cc: Wenyou Yang <Wenyou.Yang@...el.com>, linux-spi@...r.kernel.org,
linux-kernel@...r.kernel.org,
Richard Genoud <richard.genoud@...il.com>
Subject: [PATCH] spi: atmel: add support for changing message transfer speed
The only speed available was max_speed (the maximum speed declared for a
device).
This patch adds the support for spi_tranfer->speed_hz parameter.
We can now set a different speed for each spi message.
Signed-off-by: Richard Genoud <richard.genoud@...il.com>
---
drivers/spi/spi-atmel.c | 92 ++++++++++++++++++++++++++++-------------------
1 file changed, 55 insertions(+), 37 deletions(-)
diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 656ed36e729e..d0dd564cd7b3 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -694,6 +694,54 @@ static void atmel_spi_next_xfer_data(struct spi_master *master,
*plen = len;
}
+static int atmel_spi_set_xfer_speed(struct atmel_spi *as,
+ struct spi_device *spi,
+ struct spi_transfer *xfer)
+{
+ u32 scbr, csr;
+ unsigned long bus_hz;
+
+ /* v1 chips start out at half the peripheral bus speed. */
+ bus_hz = clk_get_rate(as->clk);
+ if (!atmel_spi_is_v2(as))
+ bus_hz /= 2;
+
+ /*
+ * Calculate the lowest divider that satisfies the
+ * constraint, assuming div32/fdiv/mbz == 0.
+ */
+ if (xfer->speed_hz)
+ scbr = DIV_ROUND_UP(bus_hz, xfer->speed_hz);
+ else
+ /*
+ * This can happend if max_speed is null.
+ * In this case, we set the lowest possible speed
+ */
+ scbr = 0xff;
+
+ /*
+ * If the resulting divider doesn't fit into the
+ * register bitfield, we can't satisfy the constraint.
+ */
+ if (scbr >= (1 << SPI_SCBR_SIZE)) {
+ dev_err(&spi->dev,
+ "setup: %d Hz too slow, scbr %u; min %ld Hz\n",
+ xfer->speed_hz, scbr, bus_hz/255);
+ return -EINVAL;
+ }
+ if (scbr == 0) {
+ dev_err(&spi->dev,
+ "setup: %d Hz too high, scbr %u; max %ld Hz\n",
+ xfer->speed_hz, scbr, bus_hz);
+ return -EINVAL;
+ }
+ csr = spi_readl(as, CSR0 + 4 * spi->chip_select);
+ csr = SPI_BFINS(SCBR, scbr, csr);
+ spi_writel(as, CSR0 + 4 * spi->chip_select, csr);
+
+ return 0;
+}
+
/*
* Submit next transfer for PDC.
* lock is held, spi irq is blocked
@@ -731,6 +779,8 @@ static void atmel_spi_pdc_next_xfer(struct spi_master *master,
spi_writel(as, RCR, len);
spi_writel(as, TCR, len);
+ atmel_spi_set_xfer_speed(as, msg->spi, xfer);
+
dev_dbg(&msg->spi->dev,
" start xfer %p: len %u tx %p/%08llx rx %p/%08llx\n",
xfer, xfer->len, xfer->tx_buf,
@@ -823,6 +873,7 @@ static void atmel_spi_dma_next_xfer(struct spi_master *master,
as->current_transfer = xfer;
len = xfer->len;
+ atmel_spi_set_xfer_speed(as, msg->spi, xfer);
}
if (atmel_spi_use_dma(as, xfer)) {
@@ -1264,9 +1315,8 @@ static int atmel_spi_setup(struct spi_device *spi)
{
struct atmel_spi *as;
struct atmel_spi_device *asd;
- u32 scbr, csr;
+ u32 csr;
unsigned int bits = spi->bits_per_word;
- unsigned long bus_hz;
unsigned int npcs_pin;
int ret;
@@ -1290,33 +1340,7 @@ static int atmel_spi_setup(struct spi_device *spi)
return -EINVAL;
}
- /* v1 chips start out at half the peripheral bus speed. */
- bus_hz = clk_get_rate(as->clk);
- if (!atmel_spi_is_v2(as))
- bus_hz /= 2;
-
- if (spi->max_speed_hz) {
- /*
- * Calculate the lowest divider that satisfies the
- * constraint, assuming div32/fdiv/mbz == 0.
- */
- scbr = DIV_ROUND_UP(bus_hz, spi->max_speed_hz);
-
- /*
- * If the resulting divider doesn't fit into the
- * register bitfield, we can't satisfy the constraint.
- */
- if (scbr >= (1 << SPI_SCBR_SIZE)) {
- dev_dbg(&spi->dev,
- "setup: %d Hz too slow, scbr %u; min %ld Hz\n",
- spi->max_speed_hz, scbr, bus_hz/255);
- return -EINVAL;
- }
- } else
- /* speed zero means "as slow as possible" */
- scbr = 0xff;
-
- csr = SPI_BF(SCBR, scbr) | SPI_BF(BITS, bits - 8);
+ csr = SPI_BF(BITS, bits - 8);
if (spi->mode & SPI_CPOL)
csr |= SPI_BIT(CPOL);
if (!(spi->mode & SPI_CPHA))
@@ -1363,8 +1387,8 @@ static int atmel_spi_setup(struct spi_device *spi)
asd->csr = csr;
dev_dbg(&spi->dev,
- "setup: %lu Hz bpw %u mode 0x%x -> csr%d %08x\n",
- bus_hz / scbr, bits, spi->mode, spi->chip_select, csr);
+ "setup: bpw %u mode 0x%x -> csr%d %08x\n",
+ bits, spi->mode, spi->chip_select, csr);
if (!atmel_spi_is_v2(as))
spi_writel(as, CSR0 + 4 * spi->chip_select, csr);
@@ -1414,12 +1438,6 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
}
}
- /* FIXME implement these protocol options!! */
- if (xfer->speed_hz < spi->max_speed_hz) {
- dev_dbg(&spi->dev, "can't change speed in transfer\n");
- return -ENOPROTOOPT;
- }
-
/*
* DMA map early, for performance (empties dcache ASAP) and
* better fault reporting.
--
1.7.10.4
--
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