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spi: spi-sun4i: fix early activation

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[ Upstream commit fb98bd0a13de2c9d96cb5c00c81b5ca118ac9d71 ]

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>
Link: https://patch.msgid.link/20250502095520.13825-1-alessandro.grassi@mailbox.org
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alessandro Grassi 2025-05-02 11:55:20 +02:00 • committed by Greg Kroah-Hartman
commit acfc86d988
1 changed files with 4 additions and 1 deletions
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5
drivers/spi/spi-sun4i.c
View file

@ -263,6 +263,9 @@ static int sun4i_spi_transfer_one(struct spi_master *master,
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 */
@ -403,7 +406,7 @@ 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;