linux-kernel - Re: [PATCH v2 2/2] mtd: rawnand: denali

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Date:   Thu, 12 Dec 2019 01:22:20 +0100
From:   Marek Vasut <marex@...x.de>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        linux-mtd@...ts.infradead.org
Cc:     Dinh Nguyen <dinguyen@...nel.org>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mtd: rawnand: denali_dt: add reset controlling

On 12/11/19 6:45 AM, Masahiro Yamada wrote:
[...]
> diff --git a/drivers/mtd/nand/raw/denali_dt.c b/drivers/mtd/nand/raw/denali_dt.c
> index 8b779a899dcf..9a294c3f6ec8 100644
> --- a/drivers/mtd/nand/raw/denali_dt.c
> +++ b/drivers/mtd/nand/raw/denali_dt.c
> @@ -6,6 +6,7 @@
>   */
>  
>  #include <linux/clk.h>
> +#include <linux/delay.h>
>  #include <linux/err.h>
>  #include <linux/io.h>
>  #include <linux/ioport.h>
> @@ -14,6 +15,7 @@
>  #include <linux/of.h>
>  #include <linux/of_device.h>
>  #include <linux/platform_device.h>
> +#include <linux/reset.h>
>  
>  #include "denali.h"
>  
> @@ -22,6 +24,8 @@ struct denali_dt {
>  	struct clk *clk;	/* core clock */
>  	struct clk *clk_x;	/* bus interface clock */
>  	struct clk *clk_ecc;	/* ECC circuit clock */
> +	struct reset_control *rst;	/* core reset */
> +	struct reset_control *rst_reg;	/* register reset */
>  };
>  
>  struct denali_dt_data {
> @@ -151,6 +155,14 @@ static int denali_dt_probe(struct platform_device *pdev)
>  	if (IS_ERR(dt->clk_ecc))
>  		return PTR_ERR(dt->clk_ecc);
>  
> +	dt->rst = devm_reset_control_get_optional_shared(dev, "nand");
> +	if (IS_ERR(dt->rst))
> +		return PTR_ERR(dt->rst);
> +
> +	dt->rst_reg = devm_reset_control_get_optional_shared(dev, "reg");
> +	if (IS_ERR(dt->rst_reg))
> +		return PTR_ERR(dt->rst_reg);
> +
>  	ret = clk_prepare_enable(dt->clk);
>  	if (ret)
>  		return ret;
> @@ -166,10 +178,30 @@ static int denali_dt_probe(struct platform_device *pdev)
>  	denali->clk_rate = clk_get_rate(dt->clk);
>  	denali->clk_x_rate = clk_get_rate(dt->clk_x);
>  
> -	ret = denali_init(denali);
> +	/*
> +	 * Deassert the register reset, and the core reset in this order.
> +	 * Deasserting the core reset while the register reset is asserted
> +	 * will cause unpredictable behavior in the controller.
> +	 */
> +	ret = reset_control_deassert(dt->rst_reg);
>  	if (ret)
>  		goto out_disable_clk_ecc;
>  
> +	ret = reset_control_deassert(dt->rst);
> +	if (ret)
> +		goto out_assert_rst_reg;
> +
> +	/*
> +	 * When the reset is deasserted, the initialization sequence is kicked
> +	 * (bootstrap process). The driver must wait until it finished.
> +	 * Otherwise, it will result in unpredictable behavior.
> +	 */
> +	usleep_range(200, 1000);
> +
> +	ret = denali_init(denali);
> +	if (ret)
> +		goto out_assert_rst;
> +
>  	for_each_child_of_node(dev->of_node, np) {
>  		ret = denali_dt_chip_init(denali, np);
>  		if (ret) {
> @@ -184,6 +216,10 @@ static int denali_dt_probe(struct platform_device *pdev)
>  
>  out_remove_denali:
>  	denali_remove(denali);
> +out_assert_rst:
> +	reset_control_assert(dt->rst);
> +out_assert_rst_reg:
> +	reset_control_assert(dt->rst_reg);

Maybe you can use devm_add_action_or_reset() here , like in e.g.
drivers/input/touchscreen/ili210x.c , to avoid this unwinding ?

[...]