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Date:   Tue, 29 Dec 2020 13:27:40 +0800
From:   Xu Yilun <>
Subject: [PATCH 0/2] fix the issue when xfer by spi-altera

When doing spi xfer by spi-altera, divide by 0 exception happens in
spi_transfer_wait(), This is because the xfer->speed_hz is always
clamped to 0 by spi->controller->max_speed_hz, the feature is
introduced in:

commit 9326e4f1e5dd ("spi: Limit the spi device max speed to controller's max speed")

The spi-altera doesn't have hardware indication for controller's
max_speed_hz, so its value is uninitialized as 0.

Patch #1 fixes the issue of spi_altera driver. When doing polling
mode xfer, its transfer_one() callback should return 1, to indicate
the xfer is finished. It should return 0 for irq mode xfer. With
this patch the polling mode xfer is OK as it needs no
spi_transfer_wait() anymore.

But the irq mode xfer is still broken. So Patch #2 assumes 1khz xfer
speed if the xfer->speed_hz is not assigned. I try to avoid the
divide by 0 issue and ensures a reasonable tolerant waiting time in
a generic way.

Xu Yilun (2):
  spi: altera: fix return value for altera_spi_txrx()
  spi: fix the divide by 0 error when calculating xfer waiting time

 drivers/spi/spi-altera.c | 26 ++++++++++++++------------
 drivers/spi/spi.c        |  4 +++-
 2 files changed, 17 insertions(+), 13 deletions(-)


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