On Sun, 3 Feb 2013 15:15:13 +0100, Jonas Gorski <[email protected]> wrote:
> This SPI controller does not support keeping CS asserted after sending
> a transfer.
> Since messages expected on this SPI controller are rather short, we can
> work around it for normal use cases by sending all transfers at once in
> a big full duplex stream.
>
> This means that we cannot change the speed between transfers if they
> require CS to be kept asserted, but these would have been rejected
> before anyway because of the inability of keeping CS asserted.
>
> Signed-off-by: Jonas Gorski <[email protected]>
Are you checking the state of transfer->cs_change when merging
transfers? If cs_change is set, then the transfers cannot be merged.
g.
> ---
> V1 -> V2:
> * split out rejection logic into separate patch
> * fixed return type of bcm63xx_txrx_bufs()
> * slightly reworked bcm63xx_txrx_bufs, obsoleting one local variable
>
> drivers/spi/spi-bcm63xx.c | 134
> +++++++++++++++++++++++++++++++++++----------
> 1 file changed, 106 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/spi/spi-bcm63xx.c b/drivers/spi/spi-bcm63xx.c
> index 27667c1..9578af7 100644
> --- a/drivers/spi/spi-bcm63xx.c
> +++ b/drivers/spi/spi-bcm63xx.c
> @@ -37,6 +37,8 @@
>
> #define PFX KBUILD_MODNAME
>
> +#define BCM63XX_SPI_MAX_PREPEND 15
> +
> struct bcm63xx_spi {
> struct completion done;
>
> @@ -169,13 +171,17 @@ static int bcm63xx_spi_setup(struct spi_device *spi)
> return 0;
> }
>
> -static int bcm63xx_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
> +static int bcm63xx_txrx_bufs(struct spi_device *spi, struct spi_transfer
> *first,
> + unsigned int num_transfers)
> {
> struct bcm63xx_spi *bs = spi_master_get_devdata(spi->master);
> u16 msg_ctl;
> u16 cmd;
> u8 rx_tail;
> - unsigned int timeout = 0;
> + unsigned int i, timeout = 0, prepend_len = 0, len = 0;
> + struct spi_transfer *t = first;
> + bool do_rx = false;
> + bool do_tx = false;
>
> /* Disable the CMD_DONE interrupt */
> bcm_spi_writeb(bs, 0, SPI_INT_MASK);
> @@ -183,19 +189,45 @@ static int bcm63xx_txrx_bufs(struct spi_device *spi,
> struct spi_transfer *t)
> dev_dbg(&spi->dev, "txrx: tx %p, rx %p, len %d\n",
> t->tx_buf, t->rx_buf, t->len);
>
> - if (t->tx_buf)
> - memcpy_toio(bs->tx_io, t->tx_buf, t->len);
> + if (num_transfers > 1 && t->tx_buf && t->len <= BCM63XX_SPI_MAX_PREPEND)
> + prepend_len = t->len;
> +
> + /* prepare the buffer */
> + for (i = 0; i < num_transfers; i++) {
> + if (t->tx_buf) {
> + do_tx = true;
> + memcpy_toio(bs->tx_io + len, t->tx_buf, t->len);
> +
> + /* don't prepend more than one tx */
> + if (t != first)
> + prepend_len = 0;
> + }
> +
> + if (t->rx_buf) {
> + do_rx = true;
> + /* prepend is half-duplex write only */
> + if (t == first)
> + prepend_len = 0;
> + }
> +
> + len += t->len;
> +
> + t = list_entry(t->transfer_list.next, struct spi_transfer,
> + transfer_list);
> + }
> +
> + len -= prepend_len;
>
> init_completion(&bs->done);
>
> /* Fill in the Message control register */
> - msg_ctl = (t->len << SPI_BYTE_CNT_SHIFT);
> + msg_ctl = (len << SPI_BYTE_CNT_SHIFT);
>
> - if (t->rx_buf && t->tx_buf)
> + if (do_rx && do_tx && prepend_len == 0)
> msg_ctl |= (SPI_FD_RW << bs->msg_type_shift);
> - else if (t->rx_buf)
> + else if (do_rx)
> msg_ctl |= (SPI_HD_R << bs->msg_type_shift);
> - else if (t->tx_buf)
> + else if (do_tx)
> msg_ctl |= (SPI_HD_W << bs->msg_type_shift);
>
> switch (bs->msg_ctl_width) {
> @@ -209,7 +241,7 @@ static int bcm63xx_txrx_bufs(struct spi_device *spi,
> struct spi_transfer *t)
>
> /* Issue the transfer */
> cmd = SPI_CMD_START_IMMEDIATE;
> - cmd |= (0 << SPI_CMD_PREPEND_BYTE_CNT_SHIFT);
> + cmd |= (prepend_len << SPI_CMD_PREPEND_BYTE_CNT_SHIFT);
> cmd |= (spi->chip_select << SPI_CMD_DEVICE_ID_SHIFT);
> bcm_spi_writew(bs, cmd, SPI_CMD);
>
> @@ -223,9 +255,25 @@ static int bcm63xx_txrx_bufs(struct spi_device *spi,
> struct spi_transfer *t)
> /* read out all data */
> rx_tail = bcm_spi_readb(bs, SPI_RX_TAIL);
>
> + if (do_rx && rx_tail != len)
> + return -EIO;
> +
> + if (!rx_tail)
> + return 0;
> +
> + len = 0;
> + t = first;
> /* Read out all the data */
> - if (rx_tail)
> - memcpy_fromio(t->rx_ptr, bs->rx_io, rx_tail);
> + for (i = 0; i < num_transfers; i++) {
> + if (t->rx_buf)
> + memcpy_fromio(t->rx_buf, bs->rx_io + len, t->len);
> +
> + if (t != first || prepend_len == 0)
> + len += t->len;
> +
> + t = list_entry(t->transfer_list.next, struct spi_transfer,
> + transfer_list);
> + }
>
> return 0;
> }
> @@ -252,46 +300,76 @@ static int bcm63xx_spi_transfer_one(struct spi_master
> *master,
> struct spi_message *m)
> {
> struct bcm63xx_spi *bs = spi_master_get_devdata(master);
> - struct spi_transfer *t;
> + struct spi_transfer *t, *first = NULL;
> struct spi_device *spi = m->spi;
> int status = 0;
> -
> + unsigned int n_transfers = 0, total_len = 0;
> + bool can_use_prepend = false;
> +
> + /*
> + * This SPI controller does not support keeping CS active after a
> + * transfer.
> + * Work around this by merging as many transfers we can into one big
> + * full-duplex transfers.
> + */
> list_for_each_entry(t, &m->transfers, transfer_list) {
> status = bcm63xx_spi_check_transfer(spi, t);
> if (status < 0)
> goto exit;
>
> + if (!first)
> + first = t;
> +
> + n_transfers++;
> + total_len += t->len;
> +
> + if (n_transfers == 2 && !first->rx_buf && !t->tx_buf &&
> + first->len <= BCM63XX_SPI_MAX_PREPEND)
> + can_use_prepend = true;
> + else if (can_use_prepend && t->tx_buf)
> + can_use_prepend = false;
> +
> /* we can only transfer one fifo worth of data */
> - if (t->len > bs->fifo_size) {
> + if ((can_use_prepend &&
> + total_len > (bs->fifo_size + BCM63XX_SPI_MAX_PREPEND)) ||
> + (!can_use_prepend && total_len > bs->fifo_size)) {
> dev_err(&spi->dev, "unable to do transfers larger than
> FIFO size (%i > %i)\n",
> - t->len, bs->fifo_size);
> + total_len, bs->fifo_size);
> status = -EINVAL;
> goto exit;
> }
>
> - /* CS will be deasserted directly after transfer */
> - if (t->delay_usecs) {
> - dev_err(&spi->dev, "unable to keep CS asserted after
> transfer\n");
> + /* all combined transfers have to have the same speed */
> + if (t->speed_hz != first->speed_hz) {
> + dev_err(&spi->dev, "unable to change speed between
> transfers\n");
> status = -EINVAL;
> goto exit;
> }
>
> - if (!t->cs_change &&
> - !list_is_last(&t->transfer_list, &m->transfers)) {
> - dev_err(&spi->dev, "unable to keep CS asserted between
> transfers\n");
> + /* CS will be deasserted directly after transfer */
> + if (t->delay_usecs) {
> + dev_err(&spi->dev, "unable to keep CS asserted after
> transfer\n");
> status = -EINVAL;
> goto exit;
> }
>
> - /* configure adapter for a new transfer */
> - bcm63xx_spi_setup_transfer(spi, t);
> + if (t->cs_change ||
> + list_is_last(&t->transfer_list, &m->transfers)) {
> + /* configure adapter for a new transfer */
> + bcm63xx_spi_setup_transfer(spi, first);
>
> - /* send the data */
> - status = bcm63xx_txrx_bufs(spi, t);
> - if (status)
> - goto exit;
> + /* send the data */
> + status = bcm63xx_txrx_bufs(spi, first, n_transfers);
> + if (status)
> + goto exit;
> +
> + m->actual_length += total_len;
>
> - m->actual_length += t->len;
> + first = NULL;
> + n_transfers = 0;
> + total_len = 0;
> + can_use_prepend = false;
> + }
> }
> exit:
> m->status = status;
> --
> 1.7.10.4
>
--
Grant Likely, B.Sc, P.Eng.
Secret Lab Technologies, Ltd.
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