Re: [PATCH] pxa2xx_spi: wait_rx_stall before deasserting CS on PIO mode

[Ned Forrester <nforrester-/d+BM93fTQY@public.gmane.org>]

Daniel Ribeiro wrote:
> Em Qui, 2008-09-11 Ã s 10:41 -0700, David Brownell escreveu:
> Yes, i guess i really should use spi_setup().
> My current code is:
> 
>         spi_message_init(&m);
>         t.len = 4;
>         t.tx_buf = (u8 *)data;
>         t.rx_buf = (u8 *)data;
>         t.bits_per_word = 32;
>         t.delay_usecs = 0;
>         t.cs_change = 0;
>         t.speed_hz = 13000000;
>         spi_message_add_tail(&t, &m);
>         return spi_sync(pcap.spi, &m);
> 
> I noted that if i dont set .delay_usecs it gets a default huge value,
> same with .speed_hz, it dont use spi_board_info->max_speed_hz as
> default. Would calling spi_setup() on my driver init solve this? Or is
> this yet another issue?

In a past message, you showed the automatic declarations that went with
the above code:

>	struct spi_transfer t;
>	struct spi_message m;

While spi_message_init() zeros the memory in "m", you don't show any
code above, other than your assignments, that clears the memory in "t".
Thus, if you omit the assignments for t.delay_usecs or t.speed_hz (or
any other member of t), then you are passing uninitialized memory.  You
could use memset to clear t, or dynamically allocate zeroed memory.

Normally, you use the per-transfer values:

	t.bits_per_word
	t.speed_hz

only when you need to make them different from the default values set
when you previously called spi_setup(), and the values of:

	t.delay_usecs
	t.cs_change

when you need control over the changes in CS between transfers, and
optionally a delay prior to changes in CS.  Errors in handling these
last two were addressed by the patch you tested, and which David pushed
recently.

-- 
Ned Forrester                                       nforrester-/d+BM93fTQY@public.gmane.org
Oceanographic Systems Lab                                  508-289-2226
Applied Ocean Physics and Engineering Dept.
Woods Hole Oceanographic Institution          Woods Hole, MA 02543, USA
http://www.whoi.edu/sbl/liteSite.do?litesiteid=7212
http://www.whoi.edu/hpb/Site.do?id=1532
http://www.whoi.edu/page.do?pid=10079


-------------------------------------------------------------------------
This SF.Net email is sponsored by the Moblin Your Move Developer's challenge
Build the coolest Linux based applications with Moblin SDK & win great prizes
Grand prize is a trip for two to an Open Source event anywhere in the world
http://moblin-contest.org/redirect.php?banner_id=100&url=/