| Message ID | 20250502095520.13825-1-alessandro.grassi@mailbox.org |
|---|---|
| State | Accepted |
| Commit | fb98bd0a13de2c9d96cb5c00c81b5ca118ac9d71 |
| Headers | show |
| Series | spi: spi-sun4i: fix early activation | expand |
On Fri, 02 May 2025 11:55:20 +0200, Alessandro Grassi wrote: > The SPI interface is activated before the CPOL setting is applied. In > that moment, the clock idles high and CS goes low. After a short delay, > CPOL and other settings are applied, which may cause the clock to change > state and idle low. This transition is not part of a clock cycle, and it > can confuse the receiving device. > > To prevent this unexpected transition, activate the interface while CPOL > and the other settings are being applied. > > [...] Applied to https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next Thanks! [1/1] spi: spi-sun4i: fix early activation commit: fb98bd0a13de2c9d96cb5c00c81b5ca118ac9d71 All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted. You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed. If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced. Please add any relevant lists and maintainers to the CCs when replying to this mail. Thanks, Mark
diff --git a/drivers/spi/spi-sun4i.c b/drivers/spi/spi-sun4i.c index f89826d7dc49..aa92fd5a35a9 100644 --- a/drivers/spi/spi-sun4i.c +++ b/drivers/spi/spi-sun4i.c @@ -264,6 +264,9 @@ static int sun4i_spi_transfer_one(struct spi_controller *host, else reg |= SUN4I_CTL_DHB; + /* Now that the settings are correct, enable the interface */ + reg |= SUN4I_CTL_ENABLE; + sun4i_spi_write(sspi, SUN4I_CTL_REG, reg); /* Ensure that we have a parent clock fast enough */ @@ -404,7 +407,7 @@ static int sun4i_spi_runtime_resume(struct device *dev) } sun4i_spi_write(sspi, SUN4I_CTL_REG, - SUN4I_CTL_ENABLE | SUN4I_CTL_MASTER | SUN4I_CTL_TP); + SUN4I_CTL_MASTER | SUN4I_CTL_TP); return 0;
The SPI interface is activated before the CPOL setting is applied. In that moment, the clock idles high and CS goes low. After a short delay, CPOL and other settings are applied, which may cause the clock to change state and idle low. This transition is not part of a clock cycle, and it can confuse the receiving device. To prevent this unexpected transition, activate the interface while CPOL and the other settings are being applied. Signed-off-by: Alessandro Grassi <alessandro.grassi@mailbox.org> --- drivers/spi/spi-sun4i.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)