Re: [PATCH] spi: fsl_spi: Don't change speed while chipselect is active

Hi Christophe,

On Wed, 14 Dec 2022 14:41:33 +0100 Christophe Leroy christophe.leroy@csgroup.eu wrote:

Commit c9bfcb315104 ("spi_mpc83xx: much improved driver") made modifications to the driver to not perform speed changes while chipselect is active. But those changes where lost with the convertion to tranfer_one.

Previous implementation was allowing speed changes during message transfer when cs_change flag was set. At the time being, core SPI does not provide any feature to change speed while chipselect is off, so do not allow any speed change during message transfer, and perform the transfer setup in prepare_message in order to set correct speed while chipselect is still off.

Reported-by: Herve Codina herve.codina@bootlin.com Fixes: 64ca1a034f00 ("spi: fsl_spi: Convert to transfer_one") Cc: stable@vger.kernel.org Signed-off-by: Christophe Leroy christophe.leroy@csgroup.eu Tested-by: Herve Codina herve.codina@bootlin.com

---

drivers/spi/spi-fsl-spi.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c index 731624f157fc..93152144fd2e 100644 --- a/drivers/spi/spi-fsl-spi.c +++ b/drivers/spi/spi-fsl-spi.c @@ -333,13 +333,26 @@ static int fsl_spi_prepare_message(struct spi_controller *ctlr, { struct mpc8xxx_spi *mpc8xxx_spi = spi_controller_get_devdata(ctlr); struct spi_transfer *t;

• struct spi_transfer *first;
• first = list_first_entry(&m->transfers, struct spi_transfer,

• 		 transfer_list);
  

/* * In CPU mode, optimize large byte transfers to use larger * bits_per_word values to reduce number of interrupts taken.

• *
  

• * Some glitches can appear on the SPI clock when the mode changes.
  

• * Check that there is no speed change during the transfer and set it up
  

• * now to change the mode without having a chip-select asserted.
  

  */

• if (!(mpc8xxx_spi->flags & SPI_CPM_MODE)) {

• list_for_each_entry(t, &m->transfers, transfer_list) {
  

• list_for_each_entry(t, &m->transfers, transfer_list) {

• if (t->speed_hz != first->speed_hz) {
  

• 	dev_err(&m->spi->dev,
  

• 		"speed_hz cannot change during message.\n");
  

• 	return -EINVAL;
  

• }
  

• if (!(mpc8xxx_spi->flags & SPI_CPM_MODE)) {
  if (t->len < 256 || t->bits_per_word != 8)
  	continue;
  if ((t->len & 3) == 0)
  

@@ -348,7 +361,7 @@ static int fsl_spi_prepare_message(struct spi_controller *ctlr, t->bits_per_word = 16; } }

• return 0;

• return fsl_spi_setup_transfer(m->spi, first);

} static int fsl_spi_transfer_one(struct spi_controller *controller,

Looks good to me.

Reviewed-by: Herve Codina herve.codina@bootlin.com

Regards, Hervé