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From: Feng Tang <feng.tang@intel.com>
To: Dirk Brandewie <dirk.brandewie@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"spi-devel-general@lists.sourceforge.net"
	<spi-devel-general@lists.sourceforge.net>
Subject: Re: [PATCH 08/11] spi-dw: Ensure fifo lenght is set.
Date: Thu, 23 Jun 2011 11:21:03 +0800	[thread overview]
Message-ID: <20110623112103.0434c73d@feng-i7> (raw)
In-Reply-To: <4E02AC85.90300@gmail.com>

On Thu, 23 Jun 2011 11:01:25 +0800
Dirk Brandewie <dirk.brandewie@gmail.com> wrote:


> >> -	/*
> >> -	 * Try to detect the FIFO depth if not set by interface
> >> driver,
> >> -	 * the depth could be from 2 to 256 from HW spec
> >> -	 */
> >> -	if (!dws->fifo_len) {
> >> -		u32 fifo;
> >> -		for (fifo = 2; fifo<= 257; fifo++) {
> >> -			dw_writew(dws, txfltr, fifo);
> >> -			if (fifo != dw_readw(dws, txfltr))
> >> -				break;
> >> -		}
> >> -
> >> -		dws->fifo_len = (fifo == 257) ? 0 : fifo;
> >> -		dw_writew(dws, txfltr, 0);
> >> -	}
> >>   }
> >
> > This code is requested by other community developers, the FIFO
> > length is adjustable for the dw_spi core when deployed on
> > different platforms, for those who are not certain about the
> > FIFO len, they can use this code to probe the FIFO len.
> >
> > So we need to keep it.
> >
> 
> Then I have bad documentation because document I have says that you
> can NOt write to txfltr while the controller is enabled.  The sizing
> routine as it stands can't work for the implementation in Moorsetown
> and Medfield.
> 
> If there are other SOC's that are implementing different semantics
> for txfltr we will need to handle this differently and do some
> runtime detection of how the fifo should be sized.
> 
> Can you give ne a reference to the person that requiested the sizing
> code so I can follow-up

Git-show c587b6fa0510

commit c587b6fa05106606053fc5e8e344f07cd34ace23
Author: Feng Tang <feng.tang@intel.com>
Date:   Thu Jan 21 10:41:10 2010 +0800

    spi/dw_spi: add a FIFO depth detection

    FIFO depth is configurable for each implementation of DW core,
    so add a depth detection for those interface drivers who don't set
    the fifo_len explicitly

    Signed-off-by: Feng Tang <feng.tang@intel.com>
    Acked-by: Jean-Hugues Deschenes <jean-hugues.deschenes@octasic.com>
    Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

I added the code per request from Jean-Hugues Deschenes.

Recently Alek Du has tested this code on his Medfield platform.

Thanks,
Feng

  reply	other threads:[~2011-06-23  3:21 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-23  2:00 [PATCH 00/11] RFC spi-dw updates dirk.brandewie
2011-06-23  2:00 ` [PATCH 01/11] spi-dw: expose platform data stucture dirk.brandewie
2011-06-23  3:47   ` Grant Likely
2011-06-23  4:00     ` Dirk Brandewie
2011-06-23  4:03       ` glikely@secretlab.ca
2011-06-23  4:37         ` Dirk Brandewie
2011-06-23  5:06           ` glikely@secretlab.ca
2011-06-23  5:16             ` Dirk Brandewie
     [not found] ` <1308794413-11069-1-git-send-email-dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2011-06-23  2:00   ` [PATCH 02/11] spi-dw: update function naming convention to match file naming dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  2:00   ` [PATCH 03/11] spi-dw: change MRST prefix to generic prefix dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  2:00   ` [PATCH 04/11] spi-dw: remove unused definition dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  2:00   ` [PATCH 05/11] spi-dw: split spi_dw_enable_chip() into spi_dw_enable()/spi_dw_disable() dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  2:00   ` [PATCH 06/11] spi-dw: Force error on out of range chip select dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  3:51     ` Grant Likely
2011-06-23  4:13       ` Dirk Brandewie
2011-06-23  2:00   ` [PATCH 07/11] spi-dw: Set number of available chip selects correctly dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  3:53     ` Grant Likely
2011-06-23  2:00   ` [PATCH 08/11] spi-dw: Ensure fifo lenght is set dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  2:41     ` Feng Tang
2011-06-23  3:01       ` Dirk Brandewie
2011-06-23  3:21         ` Feng Tang [this message]
2011-06-23  3:55     ` Grant Likely
2011-06-23  4:20       ` Dirk Brandewie
2011-06-23  2:00   ` [PATCH 09/11] spi-dw: Fix condition in spi_dw_{writer/reader} dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  2:45     ` Feng Tang
2011-06-23  3:09       ` Dirk Brandewie
2011-06-23  3:25         ` Feng Tang
2011-06-23  3:30           ` Dirk Brandewie
2011-06-23  5:09             ` Feng Tang
2011-06-23  2:00   ` [PATCH 11/11] spi-dw: remove noop else clause dirk.brandewie-Re5JQEeQqe8AvxtiuMwx3w
2011-06-23  2:47     ` Feng Tang
2011-06-23  3:13       ` Dirk Brandewie
2011-06-23  2:00 ` [PATCH 10/11] spi-dw: Move checking of max_speed_hz value to be a prerequisite in spi_dw_setup dirk.brandewie
2011-06-23  2:39 ` [PATCH 00/11] RFC spi-dw updates Feng Tang

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