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

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Message-ID: <4FF8F58FAA9D5D4193D4E554E4352C5902C52798@XAP-PVEXMBX02.xlnx.xilinx.com>
Date:	Wed, 20 Jan 2016 05:21:24 +0000
From:	Lakshmi Sai Krishna Potthuri 
	<lakshmi.sai.krishna.potthuri@...inx.com>
To:	Chen-Yu Tsai <wens@...e.org>
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 <devicetree@...r.kernel.org>,
	Harini Katakam <harinik@...inx.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Anirudha Sarangi <anirudh@...inx.com>,
	Punnaiah Choudary Kalluri <punnaia@...inx.com>,
	linux-arm-kernel <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: Chen-Yu Tsai [mailto:wens@...e.org]
> Sent: Tuesday, January 19, 2016 8:32 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; Harini
> Katakam; linux-mmc@...r.kernel.org; linux-kernel; Lakshmi Sai Krishna
> Potthuri; Anirudha Sarangi; Punnaiah Choudary Kalluri; linux-arm-kernel
> Subject: Re: [LINUX PATCH 1/5] mmc: Workaround for the issue in auto
> tuning mode.
>
> Hi,
>
> On Tue, Jan 19, 2016 at 10:17 PM, P L Sai Krishna
> <lakshmi.sai.krishna.potthuri@...inx.com> wrote:
> > During the auto tuning mode of SDR104, a couple of transactions on
> > rx_tap_value which are not incremental or decremental by 1.
> > Since the DLL supports only increment/decrement by 1 during dynamic
> > change, observed unexpected delays during both these transactions.
> > The first transaction occurs when the tap value reached 0x1F, it will
> > reset to 0x0 and go till 0x7. This transaction can be avoided by
> > changing the corecfg_dis1p5xtuningcnt to 1'b1 which is currently tied
> > to 1'b0 in the RTL.
> > The second transaction occurs after the tuning is completed.
> > Once the tuning is done, the tuning fsm in the host controller
> > calculates the average pattern match and will write the value on the
> > rx tap value. Therefore observed a transaction from 0x7 to the final
> > value which need not be a increment/decrement value.
> > Because of this issue DLL tuning will not be accurate and SDR50,
> > SDR104 & HS200 modes may not work.
> >
> > This patch adds workaround to change the SD clock after tuning done to
> > provide accurate DLL tuning for SDR50,
> > SD104 & HS200 modes.
> >
> > After receiving the tuning done, program "SDCLK Frequency Select"
> > of clock control register with a value different from the desired
> > value. Wait for the "Internal Clock Stable" bit of the clock control
> > register and program the desired frequency.
>
> Does this series apply to any non-Arasan or non-sdhci mmc hosts?
> The subject does not indicate a specific platform.

This series is applicable only for Zynq Ultrascal+ MPSoC which
uses Arasan SDHCI.
Sorry, I will change the description to indicate the same.
The DT property used is made generic but the tuning used is
Specific to this SoC.

Regards
Sai Krishna


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