linux-kernel - [PATCH 4/5] spi: spi-nxp-fspi: correct the clock rate for DTR mode

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Message-Id: <20250916-flexspi-ddr-v1-4-69358b5dc862@nxp.com>
Date: Tue, 16 Sep 2025 15:56:43 +0800
From: Haibo Chen <haibo.chen@....com>
To: Han Xu <han.xu@....com>, Yogesh Gaur <yogeshgaur.83@...il.com>, 
 Mark Brown <broonie@...nel.org>
Cc: linux-spi@...r.kernel.org, imx@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, Haibo Chen <haibo.chen@....com>
Subject: [PATCH 4/5] spi: spi-nxp-fspi: correct the clock rate for DTR mode

For DTR mode, flexspi will automatically div 2 of the root clock
and output to device. the formula is:
device_clock = root_clock / (is_dtr ? 2 : 1);

So correct the clock rate setting for DTR mode to get the max
performance.

Signed-off-by: Haibo Chen <haibo.chen@....com>
---
 drivers/spi/spi-nxp-fspi.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-nxp-fspi.c b/drivers/spi/spi-nxp-fspi.c
index be1e56072b94f38af934556055e321d9834bb07b..15b094e8e892f0b61c1f320bba897fa1f588be91 100644
--- a/drivers/spi/spi-nxp-fspi.c
+++ b/drivers/spi/spi-nxp-fspi.c
@@ -806,10 +806,15 @@ static void nxp_fspi_select_mem(struct nxp_fspi *f, struct spi_device *spi,
 
 	nxp_fspi_select_rx_sample_clk_source(f, op_is_dtr);
 
-	if (op_is_dtr)
+	if (op_is_dtr) {
 		f->flags |= FSPI_DTR_MODE;
-	else
+		/* For DTR mode, flexspi will default div 2 and output to device.
+		 * so here to config the root clock to 2 * device rate.
+		 */
+		rate = rate * 2;
+	} else {
 		f->flags &= ~FSPI_DTR_MODE;
+	}
 
 	nxp_fspi_clk_disable_unprep(f);
 

-- 
2.34.1