linux-kernel - Re: [PATCH v3 5/5] mmc: sdhci-of-aspeed: Assert/Deassert reset signal before probing eMMC

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Date:   Fri, 7 May 2021 14:24:17 +0800
From:   Steven Lee <steven_lee@...eedtech.com>
To:     Andrew Jeffery <andrew@...id.au>
CC:     Philipp Zabel <p.zabel@...gutronix.de>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ryan Chen <ryanchen.aspeed@...il.com>,
        "moderated list:ASPEED SD/MMC DRIVER" <linux-aspeed@...ts.ozlabs.org>,
        "moderated list:ASPEED SD/MMC DRIVER" <openbmc@...ts.ozlabs.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM/ASPEED MACHINE SUPPORT" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        Hongwei Zhang <Hongweiz@....com>,
        Ryan Chen <ryan_chen@...eedtech.com>,
        Chin-Ting Kuo <chin-ting_kuo@...eedtech.com>
Subject: Re: [PATCH v3 5/5] mmc: sdhci-of-aspeed: Assert/Deassert reset
 signal before probing eMMC

The 05/07/2021 09:32, Andrew Jeffery wrote:
> 
> 
> On Thu, 6 May 2021, at 19:54, Philipp Zabel wrote:
> > Hi Steven,
> > 
> > On Thu, May 06, 2021 at 06:03:12PM +0800, Steven Lee wrote:
> > > +	if (info) {
> > > +		if (info->flag & PROBE_AFTER_ASSET_DEASSERT) {
> > > +			sdc->rst = devm_reset_control_get(&pdev->dev, NULL);
> > 
> > Please use devm_reset_control_get_exclusive() or
> > devm_reset_control_get_optional_exclusive().
> > 
> > > +			if (!IS_ERR(sdc->rst)) {
> > 
> > Please just return errors here instead of ignoring them.
> > The reset_control_get_optional variants return NULL in case the
> > device node doesn't contain a resets phandle, in case you really
> > consider this reset to be optional even though the flag is set?
> 
> It feels like we should get rid of the flag and leave it to the 
> devicetree.
> 

Do you mean adding a flag, for instance, "mmc-reset" in the
device tree and call of_property_read_bool() in aspeed_sdc_probe()?

> I'm still kind of surprised it's not something we want to do for the 
> 2400 and 2500 as well.
> 

Per discussion with the chip designer, AST2400 and AST2500 doesn't need
this implementation since the chip design is different to AST2600.

> Andrew