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Commit acfc86d9 authored by Alessandro Grassi's avatar Alessandro Grassi Committed by Greg Kroah-Hartman
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spi: spi-sun4i: fix early activation 



[ 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: default avatarAlessandro Grassi <alessandro.grassi@mailbox.org>
Link: https://patch.msgid.link/20250502095520.13825-1-alessandro.grassi@mailbox.org


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent dd1283d7

drivers/spi/spi-sun4i.c

+4 −1
Original line number Diff line number Diff line
@@ -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;