linux-kernel - Re: [PATCH] reset: axs10x: Implement assert and deassert callbacks

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Message-ID: <1554723600.2797.58.camel@synopsys.com>
Date:   Mon, 8 Apr 2019 11:40:00 +0000
From:   Eugeniy Paltsev <eugeniy.paltsev@...opsys.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "vitor.soares@...opsys.com" <vitor.soares@...opsys.com>
CC:     Joao Pinto <joao.pinto@...opsys.com>,
        "nelson.costa@...opsys.com" <nelson.costa@...opsys.com>,
        Luis de Oliveira <luis.oliveira@...opsys.com>,
        "eugeniy.Paltsev@...opsys.com" <eugeniy.paltsev@...opsys.com>,
        "gustavo.pimentel@...opsys.com" <gustavo.pimentel@...opsys.com>,
        "Alexey Brodkin" <alexey.brodkin@...opsys.com>,
        "jose.abreu@...opsys.com" <jose.abreu@...opsys.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "pedrom.sousa@...opsys.com" <pedrom.sousa@...opsys.com>
Subject: Re: [PATCH] reset: axs10x: Implement assert and deassert callbacks

Hi Vitor,

On Mon, 2019-04-08 at 12:31 +0200, Vitor Soares wrote:
> Some custom IP-block connected to ARC AXS10x board need assert and
> deassert functions to control reset signal of selected peripherals.
> 
> This patch improve AXS10x reset driver by adding assert and deassert
> callbacks.


In the AXS10x reset driver only 'reset' callback is intentionally implemented.
AXS10x is FPGA based boards and with our default firmware AXS10x reset register is implemented as self-deasserted.

Do you have somehow modified AXS10x firmware where reset register is not self-deasserted?
In that case "simple-reset" driver will be suitable for you, I guess.
Otherwise this implementation is incorrect - there should be no 'assert' for reset controller with self-deasserted logic.


> 
> Signed-off-by: Vitor Soares <vitor.soares@...opsys.com>
> 
> Cc: Eugeniy Paltsev <eugeniy.Paltsev@...opsys.com>
> Cc: Alexey Brodkin <abrodkin@...opsys.com>
> Cc: Joao Pinto <jpinto@...opsys.com>
> Cc: Jose Abreu <jose.abreu@...opsys.com>
> Cc: Luis Oliveira <lolivei@...opsys.com>
> Cc: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
> Cc: Nelson Costa <nelson.costa@...opsys.com>
> Cc: Pedro Sousa <pedrom.sousa@...opsys.com>
> Cc: Philipp Zabel <p.zabel@...gutronix.de>
> ---
>  drivers/reset/reset-axs10x.c | 30 +++++++++++++++++++++++++++++-
>  1 file changed, 29 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/reset/reset-axs10x.c b/drivers/reset/reset-axs10x.c
> index a854ef41..12dac8b 100644
> --- a/drivers/reset/reset-axs10x.c
> +++ b/drivers/reset/reset-axs10x.c
> @@ -37,8 +37,36 @@ static int axs10x_reset_reset(struct reset_controller_dev *rcdev,
>  	return 0;
>  }
>  
> +static int axs10x_reset_assert(struct reset_controller_dev *rcdev,
> +			       unsigned long id)
> +{
> +	struct axs10x_rst *rst = to_axs10x_rst(rcdev);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&rst->lock, flags);
> +	writel(readl(rst->regs_rst) & ~BIT(id), rst->regs_rst);
> +	spin_unlock_irqrestore(&rst->lock, flags);
> +
> +	return 0;
> +}
> +
> +static int axs10x_reset_deassert(struct reset_controller_dev *rcdev,
> +				 unsigned long id)
> +{
> +	struct axs10x_rst *rst = to_axs10x_rst(rcdev);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&rst->lock, flags);
> +	writel(readl(rst->regs_rst) | BIT(id), rst->regs_rst);
> +	spin_unlock_irqrestore(&rst->lock, flags);
> +
> +	return 0;
> +}
> +
>  static const struct reset_control_ops axs10x_reset_ops = {
> -	.reset	= axs10x_reset_reset,
> +	.reset		= axs10x_reset_reset,
> +	.assert		= axs10x_reset_assert,
> +	.deassert	= axs10x_reset_deassert,
>  };
>  
>  static int axs10x_reset_probe(struct platform_device *pdev)
-- 
 Eugeniy Paltsev