linux-kernel - [PATCH 3.16 098/410] spi: imx: do not access registers while clocks disabled

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Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Mark Brown" <broonie@...nel.org>,
        "Stefan Agner" <stefan@...er.ch>
Subject: [PATCH 3.16 098/410] spi: imx: do not access registers while
 clocks disabled

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Agner <stefan@...er.ch>

commit d593574aff0ab846136190b1729c151c736727ec upstream.

Since clocks are disabled except during message transfer clocks
are also disabled when spi_imx_remove gets called. Accessing
registers leads to a freeeze at least on a i.MX 6ULL. Enable
clocks before disabling accessing the MXC_CSPICTRL register.

Fixes: 9e556dcc55774 ("spi: spi-imx: only enable the clocks when we start to transfer a message")
Signed-off-by: Stefan Agner <stefan@...er.ch>
Signed-off-by: Mark Brown <broonie@...nel.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/spi/spi-imx.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -943,12 +943,23 @@ static int spi_imx_remove(struct platfor
 {
 	struct spi_master *master = platform_get_drvdata(pdev);
 	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
+	int ret;
 
 	spi_bitbang_stop(&spi_imx->bitbang);
 
+	ret = clk_enable(spi_imx->clk_per);
+	if (ret)
+		return ret;
+
+	ret = clk_enable(spi_imx->clk_ipg);
+	if (ret) {
+		clk_disable(spi_imx->clk_per);
+		return ret;
+	}
+
 	writel(0, spi_imx->base + MXC_CSPICTRL);
-	clk_unprepare(spi_imx->clk_ipg);
-	clk_unprepare(spi_imx->clk_per);
+	clk_disable_unprepare(spi_imx->clk_ipg);
+	clk_disable_unprepare(spi_imx->clk_per);
 	spi_master_put(master);
 
 	return 0;