From 742d5958062488d03082a9ff01a6afb3cf7bd634 Mon Sep 17 00:00:00 2001 From: Kamal Dasu Date: Mon, 20 Apr 2020 15:08:48 -0400 Subject: spi: bcm-qspi: Drive MSPI peripheral SSb pin on cs_change As per the spi core implementation for MSPI devices when the transfer is the last one in the message, the chip may stay selected until the next transfer. On multi-device SPI busses with nothing blocking messages going to other devices, this is just a performance hint; starting a message to another device deselects this one. But in other cases, this can be used to ensure correctness. Some devices need protocol transactions to be built from a series of spi_message submissions, where the content of one message is determined by the results of previous messages and where the whole transaction ends when the chipselect goes intactive. On CS change after completing the last serial transfer, the MSPI driver drives SSb pin CDRAM register correctly according comments in core spi.h as shown below: case 1) EOM =1, cs_change =0: SSb inactive case 2) EOM =1, cs_change =1: SSb active case 3) EOM =0, cs_change =0: SSb active case 4) EOM =0, cs_change =1: SSb inactive Signed-off-by: Kamal Dasu Link: https://lore.kernel.org/r/20200420190853.45614-5-kdasu.kdev@gmail.com Signed-off-by: Mark Brown --- drivers/spi/spi-bcm-qspi.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) diff --git a/drivers/spi/spi-bcm-qspi.c b/drivers/spi/spi-bcm-qspi.c index 23d295f36c80..a4c70ac80986 100644 --- a/drivers/spi/spi-bcm-qspi.c +++ b/drivers/spi/spi-bcm-qspi.c @@ -612,19 +612,15 @@ static int update_qspi_trans_byte_count(struct bcm_qspi *qspi, if (qt->trans->cs_change && (flags & TRANS_STATUS_BREAK_CS_CHANGE)) ret |= TRANS_STATUS_BREAK_CS_CHANGE; - if (ret) - goto done; - dev_dbg(&qspi->pdev->dev, "advance msg exit\n"); if (bcm_qspi_mspi_transfer_is_last(qspi, qt)) - ret = TRANS_STATUS_BREAK_EOM; + ret |= TRANS_STATUS_BREAK_EOM; else - ret = TRANS_STATUS_BREAK_NO_BYTES; + ret |= TRANS_STATUS_BREAK_NO_BYTES; qt->trans = NULL; } -done: dev_dbg(&qspi->pdev->dev, "trans %p len %d byte %d ret %x\n", qt->trans, qt->trans ? qt->trans->len : 0, qt->byte, ret); return ret; @@ -771,7 +767,16 @@ static int write_to_hw(struct bcm_qspi *qspi, struct spi_device *spi) bcm_qspi_write(qspi, MSPI, MSPI_NEWQP, 0); bcm_qspi_write(qspi, MSPI, MSPI_ENDQP, slot - 1); - if (tstatus & TRANS_STATUS_BREAK_DESELECT) { + /* + * case 1) EOM =1, cs_change =0: SSb inactive + * case 2) EOM =1, cs_change =1: SSb stay active + * case 3) EOM =0, cs_change =0: SSb stay active + * case 4) EOM =0, cs_change =1: SSb inactive + */ + if (((tstatus & TRANS_STATUS_BREAK_DESELECT) + == TRANS_STATUS_BREAK_CS_CHANGE) || + ((tstatus & TRANS_STATUS_BREAK_DESELECT) + == TRANS_STATUS_BREAK_EOM)) { mspi_cdram = read_cdram_slot(qspi, slot - 1) & ~MSPI_CDRAM_CONT_BIT; write_cdram_slot(qspi, slot - 1, mspi_cdram); -- cgit v1.2.3