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

[Lakshmi Sai Krishna Potthuri]

Hi,

> -----Original Message-----
> From: Chen-Yu Tsai [mailto:wens at csie.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 at atmel.com; Rob Herring; Pawel Moll; Mark Rutland; Ian
> Campbell; Kumar Gala; Suman Tripathi; Shawn Lin; devicetree; Harini
> Katakam; linux-mmc at vger.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 at xilinx.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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