spi: spi-sun4i: fix early activation

[ Upstream commit fb98bd0 ]

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>
(cherry picked from commit e99de950330510b0da9cb4a1e326ac3930c30a23)

Author: alessandro-g89

drivers/spi/spi-sun4i.c

@@ -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;