Re: [PATCH/RFC] simple SPI controller on PXA2xx SSP port, refresh

[Mike Lee <eemike@gmail.com>]

Hi stephen

On 11/2/05, Stephen Street <stephen@streetfiresound.com> wrote:
> On Sun, 2005-10-30 at 02:25 +0800, Mike Lee wrote:
> > Also, in your pxa_spi driver, you always read before write in the
> > interrupt handler. If rx and tx is pointing to the same buffer,
> > reading data will always overwrite the tx data. why not write before
> > read?
> See above. Must write to read.
I found that i misunderstand your coding. i got your idea.

> I never found any documentation on the net, usually the data-sheet for
> the chip you are talking to specifies the SPI requirements (master,
> slave, clocks, chip selects, etc). Can you send me a link to the chip?
>
It is too bad that no good reference document for development.
I am now using i.MX Soc which is ARM920 core and embedded 2 SPI bus.
You can download the datasheet from freescale web site.

Actually, i am now available to use your loopback driver on my SPI
controller driver. But only limited to PIO mode, and i get stuck on
DMA mode because of trigger problem of SPI module, I am now trying
very hard to solve that.

In my driver, there is a little bug that i could not rmmod the driver.
it will stop at unregistering device. Below is a debug msg dump. it
seem to stop at down_write(&device_subsys.rwsem) in device_del
------------------------------------------------------------
/mnt/tmpfs/tmp # insmod imx_spi.ko
bus platform: add driver imx-spi
CLASS: registering class device: ID = 'spi1'
imx-spi imx-spi.0: registered master spi1
 spi1.1-loopback: setup finish
DEV: registering device: ID = 'spi1.1-loopback'
bus spi: add device spi1.1-loopback
imx-spi imx-spi.0: registered child spi1.1-loopback
bound device 'imx-spi.0' to driver 'imx-spi'
CLASS: registering class device: ID = 'spi2'
imx-spi imx-spi.1: registered master spi2
bound device 'imx-spi.1' to driver 'imx-spi'
/mnt/tmpfs/tmp # rmmod imx_spi.ko
bus platform: remove driver imx-spi
DEV: Unregistering device. ID = 'spi1.1-loopback'

------------------------------------------------------------


Some question on SPI subsystem:
I really get confused on the structure on the whole system. e.g. the
platform_data and controller_data in board_info.  What are thier
purposes?
Also i found that spi_register_board_info is declared as __init, that
mean i can not register board info as a module, is it because there is
no 'real' probe on SPI bus? (this comsume me time to reflash my board
to debug)
I know that SDIO could have a SPI mode. Could SPI subsystem be used to
control SDIO device?

Sorry for my annoying questions.

Thanks for helping
Mike,Lee