linux-kernel - RE: [LINUX PATCH 1/5] mmc: Workaround for the issue in auto tuning mode.

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Message-ID: <4FF8F58FAA9D5D4193D4E554E4352C5902C527CE@XAP-PVEXMBX02.xlnx.xilinx.com>
Date:	Wed, 20 Jan 2016 06:02:12 +0000
From:	Lakshmi Sai Krishna Potthuri 
	<lakshmi.sai.krishna.potthuri@...inx.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Michal Simek <michals@...inx.com>,
	Soren Brinkmann <sorenb@...inx.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Kevin Hao <haokexin@...il.com>,
	"Emil P. Lenchak" <emill@...inx.com>,
	Tobias Klauser <tklauser@...tanz.ch>,
	"Sudeep Holla" <Sudeep.Holla@....com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Jisheng Zhang <jszhang@...vell.com>,
	"Ivan T. Ivanov" <ivan.ivanov@...aro.org>,
	Scott Branden <sbranden@...adcom.com>,
	Vincent Yang <vincent.yang.fujitsu@...il.com>,
	Haibo Chen <haibo.chen@...escale.com>,
	Marek Vasut <marex@...x.de>,
	"ludovic.desroches@...el.com" <ludovic.desroches@...el.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"Suman Tripathi" <stripathi@....com>,
	Shawn Lin <shawn.lin@...k-chips.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Harini Katakam <harinik@...inx.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Anirudha Sarangi <anirudh@...inx.com>,
	Punnaiah Choudary Kalluri <punnaia@...inx.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [LINUX PATCH 1/5] mmc: Workaround for the issue in auto tuning
 mode.

Hi,

> -----Original Message-----
> From: Russell King - ARM Linux [mailto:linux@....linux.org.uk]
> Sent: Tuesday, January 19, 2016 11:28 PM
> To: Lakshmi Sai Krishna Potthuri
> Cc: Michal Simek; Soren Brinkmann; Ulf Hansson; Kevin Hao; Emil P. Lenchak;
> Tobias Klauser; Sudeep Holla; Adrian Hunter; Jisheng Zhang; Ivan T. Ivanov;
> Scott Branden; Vincent Yang; Haibo Chen; Marek Vasut;
> ludovic.desroches@...el.com; Rob Herring; Pawel Moll; Mark Rutland; Ian
> Campbell; Kumar Gala; Suman Tripathi; Shawn Lin;
> devicetree@...r.kernel.org; Harini Katakam; linux-mmc@...r.kernel.org;
> linux-kernel@...r.kernel.org; Lakshmi Sai Krishna Potthuri; Anirudha
> Sarangi; Punnaiah Choudary Kalluri; linux-arm-kernel@...ts.infradead.org
> Subject: Re: [LINUX PATCH 1/5] mmc: Workaround for the issue in auto
> tuning mode.
>
<snip>
> > +
> > +   /*
> > +    * As per controller erratum, program the SDCLK Frequency
> > +    * Select of clock control register with a value, say
> > +    * clock/2. Wait for the Internal clock stable and program
> > +    * the desired frequency.
> > +    */
> > +   host->ops->set_clock(host, clock/2);
>
> The comment above says "wait for the internal clock stable" - I see no wait in
> here.  Does the code actually conform with the comment?

Wait for internal clock stable is taken care of inside
set_clock()

<snip>
> > +   if ((host->quirks2 & SDHCI_QUIRK2_BROKEN_TUNING) &&
> > +           (tuning_loop_counter >= 0) && (ctrl &
> SDHCI_CTRL_TUNED_CLK)) {
> > +           host->ops->tune_clk(host);
> > +   }
>
> Do we need this "SDHCI_QUIRK2_BROKEN_TUNING" quirk at all?  What's
> wrong
> with:
>
>       if (host->ops->tune_clk && tuning_loop_counter >= 0 &&
>           ctrl & SDHCI_CTRL_TUNED_CLK)
>               host->ops->tune_clk(host);
>
> here?
>

tune_clock is provided as part of ops and will always be present.
Other users of arasan and this driver might not have tuning broken
And won't use this manual tuning.

Regards
Sai Krishna


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