linux-kernel - Re: [PATCH] bus: imx-weim: add DT overlay support for WEIM bus

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Message-ID: <20220221083429.GT2249@dragon>
Date:   Mon, 21 Feb 2022 16:34:29 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Ivan Bornyakov <i.bornyakov@...rotek.ru>
Cc:     s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
        linux-imx@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, system@...rotek.ru
Subject: Re: [PATCH] bus: imx-weim: add DT overlay support for WEIM bus

On Mon, Feb 21, 2022 at 11:02:44AM +0300, Ivan Bornyakov wrote:
> On Mon, Feb 21, 2022 at 03:25:29PM +0800, Shawn Guo wrote:
> > On Sat, Feb 05, 2022 at 08:50:06AM +0300, Ivan Bornyakov wrote:
> > > Add OF reconfiguration notifier handler for WEIM bus to setup Chip
> > > Select timings on runtime creation of child devices.
> > > 
> > > However, it is not possible to load another DT overlay with conflicting
> > > CS timings with previously loaded overlay, even if the first one is
> > > unloaded.
> > 
> > Are we doing anything if that happens?
> > 
> 
> On device removal there is no access to device node properties, thus it
> is not possible to find out which of CS timings was configured for this
> device to clear theirs 'is_applied'.
> 
> So, if we apply one DT overlay, configure some CS timings, remove this
> overlay, apply another with conflicting timings, we will fail here
> 
> static int weim_timing_setup(...)
> {
> 	...
> 
> 	for (reg_idx = 0; reg_idx < num_regs; reg_idx++) {
> 		...
> 
> 		/* prevent re-configuring a CS that's already been configured */
> 		cst = &ts->cs[cs_idx];
> 		if (cst->is_applied && memcmp(value, cst->regs,
> 					devtype->cs_regs_count * sizeof(u32))) {
> 			dev_err(dev, "fsl,weim-cs-timing conflict on %pOF", np);
> 			return -EINVAL;
> 		}
> 		...
> 	}
> 	...
> }

Ah, right, thanks for clarifying, Ivan!

Shawn