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Date: Fri, 1 Aug 2008 17:17:16 +0200
From: Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To: David Brownell <david-b@...bell.net>
Cc: spi-devel-general@...ts.sourceforge.net, kernel@...32linux.org,
linux-kernel@...r.kernel.org,
Haavard Skinnemoen <haavard.skinnemoen@...el.com>
Subject: [PATCH 4/4] atmel_spi: Implement per-transfer protocol options
Allow drivers to set the bits_per_word and speed_hz fields of struct
spi_transfer to nonzero values. Doing this makes the transfers somewhat
more expensive as it prevents chaining and may require a division when
the transfer is submitted.
Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@...el.com>
---
drivers/spi/atmel_spi.c | 138 ++++++++++++++++++++++++++++++++++-------------
1 files changed, 100 insertions(+), 38 deletions(-)
diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index f4d60ec..0bdb4d5 100644
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -39,6 +39,7 @@ struct atmel_spi {
struct clk *clk;
struct platform_device *pdev;
struct spi_device *stay;
+ unsigned long base_hz;
u8 stopping;
struct list_head queue;
@@ -102,6 +103,15 @@ static bool atmel_spi_is_v2(void)
* field in CSR0 overrides all other CSRs.
*/
+static void atmel_spi_set_csr(struct atmel_spi *as,
+ struct spi_device *spi, u32 csr)
+{
+ if (atmel_spi_is_v2())
+ spi_writel(as, CSR0, csr);
+ else
+ spi_writel(as, CSR0 + 4 * spi->chip_select, csr);
+}
+
static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
{
struct atmel_spi_device *asd = spi->controller_state;
@@ -113,7 +123,7 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
* switches to the correct idle polarity before we
* toggle the CS.
*/
- spi_writel(as, CSR0, asd->csr);
+ atmel_spi_set_csr(as, spi, asd->csr);
spi_writel(as, MR, SPI_BF(PCS, 0x0e) | SPI_BIT(MODFDIS)
| SPI_BIT(MSTR));
spi_readl(as, MR);
@@ -169,9 +179,15 @@ static inline int atmel_spi_xfer_is_last(struct spi_message *msg,
return msg->transfers.prev == &xfer->transfer_list;
}
-static inline int atmel_spi_xfer_can_be_chained(struct spi_transfer *xfer)
+static inline bool atmel_spi_xfer_needs_preproc(struct spi_transfer *xfer)
{
- return xfer->delay_usecs == 0 && !xfer->cs_change;
+ return xfer->bits_per_word || xfer->speed_hz;
+}
+
+static inline bool atmel_spi_xfer_needs_postproc(struct spi_transfer *xfer)
+{
+ return xfer->delay_usecs == 0 || xfer->cs_change
+ || xfer->bits_per_word || xfer->speed_hz;
}
static void atmel_spi_next_xfer_data(struct spi_master *master,
@@ -228,6 +244,28 @@ static void atmel_spi_next_xfer(struct spi_master *master,
xfer = NULL;
if (xfer) {
+ /*
+ * Per-transfer overrides prevent chaining before and
+ * after, so it should be safe to alter the CSR
+ * registers here.
+ */
+ if (atmel_spi_xfer_needs_preproc(xfer)) {
+ struct spi_device *spi = msg->spi;
+ struct atmel_spi_device *asd = spi->controller_state;
+ unsigned int bits = xfer->bits_per_word;
+ u32 csr = asd->csr;
+
+ if (bits)
+ csr = SPI_BFINS(BITS, csr, bits - 8);
+ if (xfer->speed_hz) {
+ u32 scbr = DIV_ROUND_UP(as->base_hz,
+ xfer->speed_hz);
+ csr = SPI_BFINS(SCBR, csr, scbr);
+ }
+
+ atmel_spi_set_csr(as, spi, csr);
+ }
+
spi_writel(as, PTCR, SPI_BIT(RXTDIS) | SPI_BIT(TXTDIS));
len = xfer->len;
@@ -257,10 +295,12 @@ static void atmel_spi_next_xfer(struct spi_master *master,
if (remaining > 0)
len = remaining;
else if (!atmel_spi_xfer_is_last(msg, xfer)
- && atmel_spi_xfer_can_be_chained(xfer)) {
+ && !atmel_spi_xfer_needs_postproc(xfer)) {
xfer = list_entry(xfer->transfer_list.next,
struct spi_transfer, transfer_list);
len = xfer->len;
+ if (atmel_spi_xfer_needs_preproc(xfer))
+ xfer = NULL;
} else
xfer = NULL;
@@ -409,6 +449,45 @@ atmel_spi_msg_done(struct spi_master *master, struct atmel_spi *as,
atmel_spi_next_message(master);
}
+static void atmel_spi_xfer_done(struct spi_master *master,
+ struct spi_transfer *xfer, struct spi_message *msg)
+{
+ struct atmel_spi *as = spi_master_get_devdata(master);
+ msg->actual_length += xfer->len;
+
+ if (!msg->is_dma_mapped)
+ atmel_spi_dma_unmap_xfer(master, xfer);
+
+ /* REVISIT: udelay in irq is unfriendly */
+ if (xfer->delay_usecs)
+ udelay(xfer->delay_usecs);
+
+ if (xfer->bits_per_word || xfer->speed_hz) {
+ /*
+ * Protocol options were overridden by this transfer;
+ * revert to default settings.
+ */
+ struct spi_device *spi = msg->spi;
+ struct atmel_spi_device *asd = spi->controller_state;
+
+ atmel_spi_set_csr(as, spi, asd->csr);
+ }
+
+ if (atmel_spi_xfer_is_last(msg, xfer)) {
+ /* report completed message */
+ atmel_spi_msg_done(master, as, msg, 0, xfer->cs_change);
+ } else {
+ if (xfer->cs_change) {
+ cs_deactivate(as, msg->spi);
+ udelay(1);
+ cs_activate(as, msg->spi);
+ }
+
+ /* Not done yet. Submit the next transfer. */
+ atmel_spi_next_xfer(master, msg);
+ }
+}
+
static irqreturn_t
atmel_spi_interrupt(int irq, void *dev_id)
{
@@ -484,41 +563,14 @@ atmel_spi_interrupt(int irq, void *dev_id)
spi_writel(as, IDR, pending);
- if (as->current_remaining_bytes == 0) {
- msg->actual_length += xfer->len;
-
- if (!msg->is_dma_mapped)
- atmel_spi_dma_unmap_xfer(master, xfer);
-
- /* REVISIT: udelay in irq is unfriendly */
- if (xfer->delay_usecs)
- udelay(xfer->delay_usecs);
-
- if (atmel_spi_xfer_is_last(msg, xfer)) {
- /* report completed message */
- atmel_spi_msg_done(master, as, msg, 0,
- xfer->cs_change);
- } else {
- if (xfer->cs_change) {
- cs_deactivate(as, msg->spi);
- udelay(1);
- cs_activate(as, msg->spi);
- }
-
- /*
- * Not done yet. Submit the next transfer.
- *
- * FIXME handle protocol options for xfer
- */
- atmel_spi_next_xfer(master, msg);
- }
- } else {
+ if (as->current_remaining_bytes == 0)
+ atmel_spi_xfer_done(master, xfer, msg);
+ else
/*
* Keep going, we still have data to send in
* the current transfer.
*/
atmel_spi_next_xfer(master, msg);
- }
}
spin_unlock(&as->lock);
@@ -578,6 +630,7 @@ static int atmel_spi_setup(struct spi_device *spi)
bus_hz = clk_get_rate(as->clk);
if (!atmel_spi_is_v2())
bus_hz /= 2;
+ as->base_hz = bus_hz;
if (spi->max_speed_hz) {
/*
@@ -679,10 +732,19 @@ static int atmel_spi_transfer(struct spi_device *spi, struct spi_message *msg)
return -EINVAL;
}
- /* FIXME implement these protocol options!! */
- if (xfer->bits_per_word || xfer->speed_hz) {
- dev_dbg(&spi->dev, "no protocol options yet\n");
- return -ENOPROTOOPT;
+ if (xfer->bits_per_word && (xfer->bits_per_word < 8
+ || xfer->bits_per_word > 16)) {
+ dev_dbg(&spi->dev, "unsupported bits_per_word\n");
+ return -EINVAL;
+ }
+ if (xfer->speed_hz) {
+ unsigned long divider;
+ divider = DIV_ROUND_UP(as->base_hz, xfer->speed_hz);
+
+ if (divider > 255) {
+ dev_dbg(&spi->dev, "speed_hz too low\n");
+ return -EINVAL;
+ }
}
/*
--
1.5.6.3
--
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