linux-kernel - [PATCH] mtd: nand: davinci: don't acquire and enable clock

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Date:   Fri, 30 Mar 2018 20:00:51 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
CC:     Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Sekhar Nori <nsekhar@...com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>,
        David Lechner <david@...hnology.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: [PATCH] mtd: nand: davinci: don't acquire and enable clock

NAND itself is an asynchronous interface, it does not have any
clock input. DaVinci NAND driver acquires clock for AEMIF
(asynchronous external memory interface) which is an on-chip
IP to which NAND is connected.

The same clock is also enabled in AEMIF driver (either present
drivers/memory or from machine code for some older platforms).
AEMIF timing must be initialized before NAND can be accessed.
This ensures that AEMIF clock is enabled too.

Remove the superfluous clock acquisition and enable in DaVinci
NAND driver.

Tested on K2L, K2HK, K2E, DA850 EVM, DA850 LCDK in device-tree
boot and DM644x EVM in legacy boot.

Signed-off-by: Sekhar Nori <nsekhar@...com>
---
Hi Boris,

If/when this patch gets accepted, it will nice to put this on
an immutable branch others can merge. There is potential cleanup
in drivers/clock and in DaVinci machine code that will depend
on this.

Thanks,
Sekhar

 drivers/mtd/nand/raw/davinci_nand.c | 25 +------------------------
 1 file changed, 1 insertion(+), 24 deletions(-)

diff --git a/drivers/mtd/nand/raw/davinci_nand.c b/drivers/mtd/nand/raw/davinci_nand.c
index 0f09518d980f..7255a0d94374 100644
--- a/drivers/mtd/nand/raw/davinci_nand.c
+++ b/drivers/mtd/nand/raw/davinci_nand.c
@@ -27,7 +27,6 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/err.h>
-#include <linux/clk.h>
 #include <linux/io.h>
 #include <linux/mtd/rawnand.h>
 #include <linux/mtd/partitions.h>
@@ -55,7 +54,6 @@ struct davinci_nand_info {
 	struct nand_chip	chip;
 
 	struct device		*dev;
-	struct clk		*clk;
 
 	bool			is_readmode;
 
@@ -703,22 +701,6 @@ static int nand_davinci_probe(struct platform_device *pdev)
 	/* Use board-specific ECC config */
 	info->chip.ecc.mode	= pdata->ecc_mode;
 
-	ret = -EINVAL;
-
-	info->clk = devm_clk_get(&pdev->dev, "aemif");
-	if (IS_ERR(info->clk)) {
-		ret = PTR_ERR(info->clk);
-		dev_dbg(&pdev->dev, "unable to get AEMIF clock, err %d\n", ret);
-		return ret;
-	}
-
-	ret = clk_prepare_enable(info->clk);
-	if (ret < 0) {
-		dev_dbg(&pdev->dev, "unable to enable AEMIF clock, err %d\n",
-			ret);
-		goto err_clk_enable;
-	}
-
 	spin_lock_irq(&davinci_nand_lock);
 
 	/* put CSxNAND into NAND mode */
@@ -732,7 +714,7 @@ static int nand_davinci_probe(struct platform_device *pdev)
 	ret = nand_scan_ident(mtd, pdata->mask_chipsel ? 2 : 1, NULL);
 	if (ret < 0) {
 		dev_dbg(&pdev->dev, "no NAND chip(s) found\n");
-		goto err;
+		return ret;
 	}
 
 	switch (info->chip.ecc.mode) {
@@ -838,9 +820,6 @@ static int nand_davinci_probe(struct platform_device *pdev)
 	nand_cleanup(&info->chip);
 
 err:
-	clk_disable_unprepare(info->clk);
-
-err_clk_enable:
 	spin_lock_irq(&davinci_nand_lock);
 	if (info->chip.ecc.mode == NAND_ECC_HW_SYNDROME)
 		ecc4_busy = false;
@@ -859,8 +838,6 @@ static int nand_davinci_remove(struct platform_device *pdev)
 
 	nand_release(nand_to_mtd(&info->chip));
 
-	clk_disable_unprepare(info->clk);
-
 	return 0;
 }
 
-- 
2.16.2