[PATCH] mtd: rawnand: qcom: Fix clock sequencing in qcom_nandc_probe()

[Bryan O'Donoghue]

Interacting with a NAND chip on an IPQ6018 I found that the qcomsmem NAND
partition parser was returning -EPROBE_DEFER waiting for the main smem
driver to load.

This caused the board to reset. Playing about with the probe() function
shows that the problem lies in the core clock being switched off before the
nandc_unalloc() routine has completed.

If we look at how qcom_nandc_remove() tears down allocated resources we see
the expected order is

qcom_nandc_unalloc(nandc);

clk_disable_unprepare(nandc->aon_clk);
clk_disable_unprepare(nandc->core_clk);

dma_unmap_resource(&pdev->dev, nandc->base_dma, resource_size(res),
		   DMA_BIDIRECTIONAL, 0);

Tweaking probe() to both bring up and tear-down in that order removes the
reset if we end up deferring elsewhere.

Fixes: c76b78d8ec05 ("mtd: nand: Qualcomm NAND controller driver")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue at linaro.org>
---
 drivers/mtd/nand/raw/qcom_nandc.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
index 04e6f7b267064..0f41a9a421575 100644
--- a/drivers/mtd/nand/raw/qcom_nandc.c
+++ b/drivers/mtd/nand/raw/qcom_nandc.c
@@ -2,7 +2,6 @@
 /*
  * Copyright (c) 2016, The Linux Foundation. All rights reserved.
  */
-
 #include <linux/clk.h>
 #include <linux/slab.h>
 #include <linux/bitops.h>
@@ -3063,10 +3062,6 @@ static int qcom_nandc_probe(struct platform_device *pdev)
 	if (dma_mapping_error(dev, nandc->base_dma))
 		return -ENXIO;
 
-	ret = qcom_nandc_alloc(nandc);
-	if (ret)
-		goto err_nandc_alloc;
-
 	ret = clk_prepare_enable(nandc->core_clk);
 	if (ret)
 		goto err_core_clk;
@@ -3075,6 +3070,10 @@ static int qcom_nandc_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_aon_clk;
 
+	ret = qcom_nandc_alloc(nandc);
+	if (ret)
+		goto err_nandc_alloc;
+
 	ret = qcom_nandc_setup(nandc);
 	if (ret)
 		goto err_setup;
@@ -3086,15 +3085,14 @@ static int qcom_nandc_probe(struct platform_device *pdev)
 	return 0;
 
 err_setup:
+	qcom_nandc_unalloc(nandc);
+err_nandc_alloc:
 	clk_disable_unprepare(nandc->aon_clk);
 err_aon_clk:
 	clk_disable_unprepare(nandc->core_clk);
 err_core_clk:
-	qcom_nandc_unalloc(nandc);
-err_nandc_alloc:
 	dma_unmap_resource(dev, res->start, resource_size(res),
 			   DMA_BIDIRECTIONAL, 0);
-
 	return ret;
 }
 
-- 
2.33.0