Re: [U-Boot] [PATCH] spi: cadence_qspi_apb: Use 32 bit indirect read transaction when possible

On 11/30/2016 12:50 PM, Vignesh R wrote:

According to Section 11.15.4.9.1 Indirect Read Controller of K2G SoC TRM SPRUHY8D[1], the external master is only permitted to issue 32-bit data interface reads until the last word of an indirect transfer So, make sure that QSPI indirect reads are 32 bit sized except for the final read. If the rxbuf is unaligned then use bounce buffer, so that readsl() can be used instead of readsb() to avoid non 32-bit accesses.

[1]www.ti.com/lit/ug/spruhy8d/spruhy8d.pdf

Signed-off-by: Vignesh R vigneshr@ti.com

Reviewed-by: Marek Vasut marex@denx.de

Thanks!

---

drivers/spi/cadence_qspi_apb.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/cadence_qspi_apb.c b/drivers/spi/cadence_qspi_apb.c index 6ce98acf747d..160ceb23aefe 100644 --- a/drivers/spi/cadence_qspi_apb.c +++ b/drivers/spi/cadence_qspi_apb.c @@ -651,6 +651,8 @@ int cadence_qspi_apb_indirect_read_execute(struct cadence_spi_platdata *plat, { unsigned int remaining = n_rx; unsigned int bytes_to_read = 0;

• struct bounce_buffer bb;

• u8 *bb_rxbuf; int ret;

  writel(n_rx, plat->regbase + CQSPI_REG_INDIRECTRDBYTES);

@@ -659,6 +661,11 @@ int cadence_qspi_apb_indirect_read_execute(struct cadence_spi_platdata *plat, writel(CQSPI_REG_INDIRECTRD_START_MASK, plat->regbase + CQSPI_REG_INDIRECTRD);

• ret = bounce_buffer_start(&bb, (void *)rxbuf, n_rx, GEN_BB_WRITE);
• if (ret)

• return ret;
  

• bb_rxbuf = bb.bounce_buffer;
• while (remaining > 0) { ret = cadence_qspi_wait_for_data(plat); if (ret < 0) {

@@ -672,12 +679,13 @@ int cadence_qspi_apb_indirect_read_execute(struct cadence_spi_platdata *plat, bytes_to_read *= CQSPI_FIFO_WIDTH; bytes_to_read = bytes_to_read > remaining ? remaining : bytes_to_read;

• 	/* Handle non-4-byte aligned access to avoid data abort. */
  

• 	if (((uintptr_t)rxbuf % 4) || (bytes_to_read % 4))
  

• 		readsb(plat->ahbbase, rxbuf, bytes_to_read);
  

• 	else
  

• 		readsl(plat->ahbbase, rxbuf, bytes_to_read >> 2);
  

• 	rxbuf += bytes_to_read;
  

• 	readsl(plat->ahbbase, bb_rxbuf, bytes_to_read >> 2);
  

• 	if (bytes_to_read % 4)
  

• 		readsb(plat->ahbbase,
  

• 		       bb_rxbuf + rounddown(bytes_to_read, 4),
  

• 		       bytes_to_read % 4);
  

• 	bb_rxbuf += bytes_to_read;
  remaining -= bytes_to_read;
  bytes_to_read = cadence_qspi_get_rd_sram_level(plat);
  

  }

@@ -694,6 +702,7 @@ int cadence_qspi_apb_indirect_read_execute(struct cadence_spi_platdata *plat, /* Clear indirect completion status */ writel(CQSPI_REG_INDIRECTRD_DONE_MASK, plat->regbase + CQSPI_REG_INDIRECTRD);

• bounce_buffer_stop(&bb);

  return 0;

@@ -701,6 +710,7 @@ failrd: /* Cancel the indirect read */ writel(CQSPI_REG_INDIRECTRD_CANCEL_MASK, plat->regbase + CQSPI_REG_INDIRECTRD);

• bounce_buffer_stop(&bb); return ret;

}