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

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Message-ID: <20180402090314.70b1ecee@bbrezillon>
Date:   Mon, 2 Apr 2018 09:03:14 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Sekhar Nori <nsekhar@...com>
Cc:     David Lechner <david@...hnology.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Richard Weinberger <richard@....at>,
        linux-kernel@...r.kernel.org, Marek Vasut <marek.vasut@...il.com>,
        linux-mtd@...ts.infradead.org,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] mtd: nand: davinci: don't acquire and enable clock

Oh, one more thing: now that we moved parallel/raw NAND code in the raw
subdir, the subject prefix should be "mtd: rawnand: <driver>: ". No need
to send a new version for that, I'll fix it when applying, just wanted
to let you know.

On Fri, 30 Mar 2018 20:00:51 +0530
Sekhar Nori <nsekhar@...com> wrote:

> 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;
>  }
>  



-- 
Boris Brezillon, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com