linux-kernel - Re: [PATCH] ATA: pata

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Date:	Wed, 27 Apr 2011 20:38:19 +0200
From:	Stanislaw Gruszka <stf_xl@...pl>
To:	Igor Plyatov <plyatov@...il.com>
Cc:	Jeff Garzik <jgarzik@...ox.com>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ATA: pata_at91.c bugfixes

On Tue, Apr 26, 2011 at 10:38:04AM +0400, Igor Plyatov wrote:
> >On Wed, Apr 20, 2011 at 03:44:37PM +0400, Igor Plyatov wrote:
> >>* Fix "initial_timing" structure initialisation. The "struct ata_timing" must
> >>   contain 10 members, but ".dmack_hold" member was not initialised.
> >>* The AT91SAM9 microcontrollers use special coding scheme for SMC_SETUP,
> >>   SMC_PULSE, SMC_CYCLE registers.
> >>   Old driver operates correctly only with low master clock values, but
> >>   with high master clock it incorrectly calculates SMC values and stops
> >>   to operate, because SMC can be setup only to admissible ranges in special
> >>   format.
> >>   New code correctly calculates SMC registers values, adjusts calculated
> >>   to admissible ranges, enlarges cycles if required and converts values
> >>   into SMC's format.
> >>* Old driver calculates CS_SETUP and CS_PULSE cycles incorrectly
> >>   because of wrong assumptions.
> >>   New code calculates:
> >>       CS_SETUP = SETUP/2
> >If you to this, then {RD,WR}_SETUP have to be equal SETUP + SETUP/2
> >to generate proper setup (t0) time on IDE bus. I think the best way is
err, setup time is t1 

> >set CS_SETUP and CS_HOLD to 0 (what your code do if SETUP and HOLD<=1),
> >but to do this you need to take care of data float (t6z)
> 
> Why so?
> 
> This is not clear for me. Maybe we talk about different things or I
> have wrong
> understanding of ATA timings.
> Can you please look at "Standard Read Cycle" for AT91SAM9 MCU
> http://www.kicad.ru/files/AT91SAM9G20%20bus%20timing.pdf
> , CompactFlash connection schematic
> http://www.kicad.ru/files/CF%20for%20AT91SAM9%20(True%20IDE%20mode).pdf
> and comment my thoughts?
Full "External Bus Interface" section from AT91 spec is important,
because is describe how SMC works internally in CF True IDE mode.

> Here is a legend for "Standard Read Cycle" timing diagram.
> ------------------------------------------------------------------------------
> Read (NRD) signal parameters:
> * t0 = cycle = NRD_CYCLE
> * t1 = setup = NRD_SETUP
> * t2 = pulse = NRD_PULSE
> * t9 = hold = NRD_HOLD
Correct. Also t0 = t1 + t2 + t9 relation must be true.

> Chip Select (NCS) signal parameters:
> * cs_setup = NCS_RD_SETUP
> * cs_pulse = NCS_RD_PULSE
> * cs_cycle = cycle
You can setup that, but they need to have proper relations with NRD.
 
> Notes:
> * The NCS_RD_CYCLE is equal to the NRD_CYCLE for AT91SAM9, because they
>   start/finish simultaneously (HW related).
No, NCS and NRD are different signals, waveforms are different (if configured
differently in SMC controller).

> * The NCS signal is not the same as CS1, CS2 ATA signals! It used only to
>   enable data bus transceiver U2.
Well, they are different signals but connected together. All of these are 
controlled by NCS: CFCE1 (CS1), CFCE2 (CS2), CFRNW (DIR), CFCS0 (OE)
if SMC is configured in True IDE mode. 

Stanislaw
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