linux-kernel - RE: [PATCH 7/8] mmc: sdhci-of-aspeed: Remove timing phase

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Message-ID:
 <TYSPR06MB70680E58607C02FF030168E7957BA@TYSPR06MB7068.apcprd06.prod.outlook.com>
Date: Wed, 25 Jun 2025 00:22:00 +0000
From: Cool Lee <cool_lee@...eedtech.com>
To: Andrew Jeffery <andrew@...econstruct.com.au>, "adrian.hunter@...el.com"
	<adrian.hunter@...el.com>, "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
	"joel@....id.au" <joel@....id.au>, "p.zabel@...gutronix.de"
	<p.zabel@...gutronix.de>, "linux-aspeed@...ts.ozlabs.org"
	<linux-aspeed@...ts.ozlabs.org>, "openbmc@...ts.ozlabs.org"
	<openbmc@...ts.ozlabs.org>, "linux-mmc@...r.kernel.org"
	<linux-mmc@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, BMC-SW <BMC-SW@...eedtech.com>
Subject: RE: [PATCH 7/8] mmc: sdhci-of-aspeed: Remove timing phase


> >
> > > > The timing phase is no more needed since the auto tuning is
> > > > applied.
> > > >
> > >
> > > I feel this is unwise: we're now ignoring constraints set in the
> > > devicetree.
> > > Auto-tuning is fine, but I think that should be a feature that new
> > > platforms can exploit by default. Older platforms that do specify
> > > the phase values via the devicetree can be converted at the leisure
> > > of their maintainers (by removing the phase properties).
> > >
> > > Support needs to remain in the driver until there are no (aspeed-
> > > based)
> > > devicetrees specifying the phases.
> > The timing phase only works on AST2600 or newer platform which has
> > added a delay cell in the RTL.
> > The older platform AST2500, AST2400 doesn't support the timing phase.
> > It supposed no effect on older platform.
> > The old manner that a static timing value customized from devicetree
> > is inconvenient because customer needs to check waveform associated
> > with each delay taps. Once the emmc parts changed, a fixed timing
> > value may not work. That's why auto tune here instead of a static
> > value.
> 
> Sure, I understand that auto-tuning is more convenient, but in my view, there's
> no reason to remove support for static phase values for now. On the contrary,
> switching entirely to auto-tuning risks regressions for existing platforms that
> do specify static values.
> 
> Can you please drop the patch for now? We can revisit removing static value
> support in the future.

Ok, I got your point. I can make a new patch to keep static and dynamic both together. If the timing property kept then use it, otherwise try dynamic tuning. Is this OK?

> 
> Andrew