linux-kernel - Re: [PATCH v2 11/17] clk: imx: Add blk

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Date:   Wed, 26 Aug 2020 09:46:20 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Abel Vesa <abel.vesa@....com>
Cc:     Dong Aisheng <aisheng.dong@....com>, Rob Herring <robh@...nel.org>,
        Peng Fan <peng.fan@....com>, Fugang Duan <fugang.duan@....com>,
        Jacky Bai <ping.bai@....com>,
        Anson Huang <anson.huang@....com>, devicetree@...r.kernel.org,
        Stephen Boyd <sboyd@...nel.org>,
        Mike Turquette <mturquette@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        NXP Linux Team <linux-imx@....com>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Shawn Guo <shawnguo@...nel.org>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 11/17] clk: imx: Add blk_ctrl combo driver

On Tue, 2020-08-25 at 21:30 +0300, Abel Vesa wrote:
[...]
> > 	if (assert)
> > 		pm_runtime_get_sync();
> > 	spin_lock_irqsave();
> > 	/* ... */
> > 	spin_unlock_irqrestore();
> > 	if (assert && asserted_before)
> > 		pm_runtime_put();
> > 
> 
> On a second thought this doesn't work because, for the first assertion,
> the runtime put will never be called, if the asserted_before does not count
> the current assertion.

I'm not sure I follow. The first assert will increment device usage
0 -> 1, all others asserts will just temporarily increment and decrement
1 -> 2 -> 1. Isn't this just missing one
	if (!assert && !asserted_after)
		pm_runtime_put()
to do the last deassert 1 -> 0 transition?

> If it counts the current assertion, then every assertion
> will end with runtime put. None of these options work here.
>
> How about the following:
>
> 	if (assert && !test_and_set_bit(1, &drvdata->rst_hws[id].asserted))     
> 		pm_runtime_get_sync(rcdev->dev);                                
>                                                                         
> 	spin_lock_irqsave(&drvdata->lock, flags);                               
>                                                                         
> 	reg = readl(reg_addr);                                                  
> 	if (assert)                                                             
> 		writel(reg & ~(mask << shift), reg_addr);                       
> 	else                                                                    
> 		writel(reg | (mask << shift), reg_addr);                        
>                                                                         
> 	spin_unlock_irqrestore(&drvdata->lock, flags);                          
>                                                                         
> 	if (!assert && test_and_clear_bit(1, &drvdata->rst_hws[id].asserted))   
> 		pm_runtime_put(rcdev->dev);                                     
>                                                                         
> This would only call the get_sync/put once for each reset bit.

Yes, that should work. I think it is a much better idea, no more looping
through the entire reset control array.

regards
Philipp