240 lines
6.7 KiB
Diff
240 lines
6.7 KiB
Diff
From 725e81d507b1098cd275d4e3333c77c4b750fa79 Mon Sep 17 00:00:00 2001
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From: Jonas Gorski <jogo@openwrt.org>
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Date: Sun, 9 Dec 2012 01:53:05 +0100
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Subject: [PATCH V2 2/2] spi/bcm63xx: work around inability to keep CS up
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This SPI controller does not support keeping CS asserted after sending
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a transfer.
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Since messages expected on this SPI controller are rather short, we can
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work around it for normal use cases by sending all transfers at once in
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a big full duplex stream.
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This means that we cannot change the speed between transfers if they
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require CS to be kept asserted, but these would have been rejected
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before anyway because of the inability of keeping CS asserted.
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Signed-off-by: Jonas Gorski <jogo@openwrt.org>
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---
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V1 -> V2:
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* split out rejection logic into separate patch
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* fixed return type of bcm63xx_txrx_bufs()
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* slightly reworked bcm63xx_txrx_bufs, obsoleting one local variable
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drivers/spi/spi-bcm63xx.c | 134 +++++++++++++++++++++++++++++++++++----------
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1 file changed, 106 insertions(+), 28 deletions(-)
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--- a/drivers/spi/spi-bcm63xx.c
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+++ b/drivers/spi/spi-bcm63xx.c
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@@ -37,6 +37,8 @@
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#define PFX KBUILD_MODNAME
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+#define BCM63XX_SPI_MAX_PREPEND 15
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+
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struct bcm63xx_spi {
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struct completion done;
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@@ -169,13 +171,17 @@ static int bcm63xx_spi_setup(struct spi_
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return 0;
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}
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-static int bcm63xx_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
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+static int bcm63xx_txrx_bufs(struct spi_device *spi, struct spi_transfer *first,
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+ unsigned int num_transfers)
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{
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struct bcm63xx_spi *bs = spi_master_get_devdata(spi->master);
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u16 msg_ctl;
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u16 cmd;
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u8 rx_tail;
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- unsigned int timeout = 0;
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+ unsigned int i, timeout = 0, prepend_len = 0, len = 0;
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+ struct spi_transfer *t = first;
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+ bool do_rx = false;
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+ bool do_tx = false;
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/* Disable the CMD_DONE interrupt */
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bcm_spi_writeb(bs, 0, SPI_INT_MASK);
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@@ -183,19 +189,45 @@ static int bcm63xx_txrx_bufs(struct spi_
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dev_dbg(&spi->dev, "txrx: tx %p, rx %p, len %d\n",
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t->tx_buf, t->rx_buf, t->len);
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- if (t->tx_buf)
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- memcpy_toio(bs->tx_io, t->tx_buf, t->len);
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+ if (num_transfers > 1 && t->tx_buf && t->len <= BCM63XX_SPI_MAX_PREPEND)
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+ prepend_len = t->len;
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+
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+ /* prepare the buffer */
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+ for (i = 0; i < num_transfers; i++) {
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+ if (t->tx_buf) {
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+ do_tx = true;
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+ memcpy_toio(bs->tx_io + len, t->tx_buf, t->len);
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+
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+ /* don't prepend more than one tx */
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+ if (t != first)
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+ prepend_len = 0;
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+ }
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+
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+ if (t->rx_buf) {
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+ do_rx = true;
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+ /* prepend is half-duplex write only */
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+ if (t == first)
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+ prepend_len = 0;
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+ }
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+
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+ len += t->len;
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+
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+ t = list_entry(t->transfer_list.next, struct spi_transfer,
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+ transfer_list);
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+ }
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+
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+ len -= prepend_len;
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init_completion(&bs->done);
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/* Fill in the Message control register */
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- msg_ctl = (t->len << SPI_BYTE_CNT_SHIFT);
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+ msg_ctl = (len << SPI_BYTE_CNT_SHIFT);
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- if (t->rx_buf && t->tx_buf)
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+ if (do_rx && do_tx && prepend_len == 0)
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msg_ctl |= (SPI_FD_RW << bs->msg_type_shift);
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- else if (t->rx_buf)
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+ else if (do_rx)
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msg_ctl |= (SPI_HD_R << bs->msg_type_shift);
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- else if (t->tx_buf)
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+ else if (do_tx)
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msg_ctl |= (SPI_HD_W << bs->msg_type_shift);
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switch (bs->msg_ctl_width) {
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@@ -209,7 +241,7 @@ static int bcm63xx_txrx_bufs(struct spi_
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/* Issue the transfer */
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cmd = SPI_CMD_START_IMMEDIATE;
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- cmd |= (0 << SPI_CMD_PREPEND_BYTE_CNT_SHIFT);
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+ cmd |= (prepend_len << SPI_CMD_PREPEND_BYTE_CNT_SHIFT);
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cmd |= (spi->chip_select << SPI_CMD_DEVICE_ID_SHIFT);
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bcm_spi_writew(bs, cmd, SPI_CMD);
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@@ -223,9 +255,25 @@ static int bcm63xx_txrx_bufs(struct spi_
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/* read out all data */
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rx_tail = bcm_spi_readb(bs, SPI_RX_TAIL);
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+ if (do_rx && rx_tail != len)
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+ return -EIO;
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+
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+ if (!rx_tail)
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+ return 0;
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+
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+ len = 0;
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+ t = first;
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/* Read out all the data */
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- if (rx_tail)
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- memcpy_fromio(t->rx_ptr, bs->rx_io, rx_tail);
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+ for (i = 0; i < num_transfers; i++) {
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+ if (t->rx_buf)
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+ memcpy_fromio(t->rx_buf, bs->rx_io + len, t->len);
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+
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+ if (t != first || prepend_len == 0)
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+ len += t->len;
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+
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+ t = list_entry(t->transfer_list.next, struct spi_transfer,
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+ transfer_list);
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+ }
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return 0;
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}
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@@ -252,46 +300,76 @@ static int bcm63xx_spi_transfer_one(stru
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struct spi_message *m)
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{
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struct bcm63xx_spi *bs = spi_master_get_devdata(master);
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- struct spi_transfer *t;
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+ struct spi_transfer *t, *first = NULL;
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struct spi_device *spi = m->spi;
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int status = 0;
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+ unsigned int n_transfers = 0, total_len = 0;
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+ bool can_use_prepend = false;
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+ /*
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+ * This SPI controller does not support keeping CS active after a
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+ * transfer.
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+ * Work around this by merging as many transfers we can into one big
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+ * full-duplex transfers.
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+ */
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list_for_each_entry(t, &m->transfers, transfer_list) {
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status = bcm63xx_spi_check_transfer(spi, t);
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if (status < 0)
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goto exit;
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+ if (!first)
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+ first = t;
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+
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+ n_transfers++;
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+ total_len += t->len;
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+
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+ if (n_transfers == 2 && !first->rx_buf && !t->tx_buf &&
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+ first->len <= BCM63XX_SPI_MAX_PREPEND)
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+ can_use_prepend = true;
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+ else if (can_use_prepend && t->tx_buf)
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+ can_use_prepend = false;
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+
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/* we can only transfer one fifo worth of data */
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- if (t->len > bs->fifo_size) {
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+ if ((can_use_prepend &&
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+ total_len > (bs->fifo_size + BCM63XX_SPI_MAX_PREPEND)) ||
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+ (!can_use_prepend && total_len > bs->fifo_size)) {
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dev_err(&spi->dev, "unable to do transfers larger than FIFO size (%i > %i)\n",
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- t->len, bs->fifo_size);
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+ total_len, bs->fifo_size);
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status = -EINVAL;
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goto exit;
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}
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- /* CS will be deasserted directly after transfer */
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- if (t->delay_usecs) {
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- dev_err(&spi->dev, "unable to keep CS asserted after transfer\n");
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+ /* all combined transfers have to have the same speed */
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+ if (t->speed_hz != first->speed_hz) {
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+ dev_err(&spi->dev, "unable to change speed between transfers\n");
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status = -EINVAL;
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goto exit;
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}
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- if (!t->cs_change &&
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- !list_is_last(&t->transfer_list, &m->transfers)) {
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- dev_err(&spi->dev, "unable to keep CS asserted between transfers\n");
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+ /* CS will be deasserted directly after transfer */
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+ if (t->delay_usecs) {
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+ dev_err(&spi->dev, "unable to keep CS asserted after transfer\n");
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status = -EINVAL;
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goto exit;
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}
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- /* configure adapter for a new transfer */
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- bcm63xx_spi_setup_transfer(spi, t);
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-
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- /* send the data */
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- status = bcm63xx_txrx_bufs(spi, t);
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- if (status)
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- goto exit;
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-
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- m->actual_length += t->len;
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+ if (t->cs_change ||
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+ list_is_last(&t->transfer_list, &m->transfers)) {
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+ /* configure adapter for a new transfer */
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+ bcm63xx_spi_setup_transfer(spi, first);
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+
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+ /* send the data */
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+ status = bcm63xx_txrx_bufs(spi, first, n_transfers);
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+ if (status)
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+ goto exit;
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+
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+ m->actual_length += total_len;
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+
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+ first = NULL;
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+ n_transfers = 0;
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+ total_len = 0;
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+ can_use_prepend = false;
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+ }
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}
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exit:
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m->status = status;
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