Re: [PATCH 2/3] Xilinx: hwicap: Verify sync before reading idcode.

["Grant Likely" <grant.likely@secretlab.ca>]

On Mon, Mar 17, 2008 at 11:36 AM, Stephen Neuendorffer
<stephen.neuendorffer@xilinx.com> wrote:
> It appears that in some cases, the sync word might not be recognized
>  by the hardware correctly.  If this happens, then attempting to read
>  from the port results in an unrecoverable error because of the design
>  of the FPGA core.  This patch updates the code to check the status of
>  the device before reading the IDCODE, in order to avoid entering this
>  unrecoverable state.  This patch also adds additional NOOP commands
>  into the sychronization sequence, which appears to be necessary to
>  avoid the condition on some hardware.
>
>  Signed-off-by: Stephen Neuendorffer <stephen.neuendorffer@xilinx.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>

>  ---
>   drivers/char/xilinx_hwicap/xilinx_hwicap.c |   18 ++++++++++++++++++
>   1 files changed, 18 insertions(+), 0 deletions(-)
>
>  diff --git a/drivers/char/xilinx_hwicap/xilinx_hwicap.c b/drivers/char/xilinx_hwicap/xilinx_hwicap.c
>  index 304727d..5b8d646 100644
>  --- a/drivers/char/xilinx_hwicap/xilinx_hwicap.c
>  +++ b/drivers/char/xilinx_hwicap/xilinx_hwicap.c
>  @@ -250,8 +250,26 @@ static int hwicap_get_configuration_register(struct hwicap_drvdata *drvdata,
>          * Create the data to be written to the ICAP.
>          */
>         buffer[index++] = XHI_DUMMY_PACKET;
>  +       buffer[index++] = XHI_NOOP_PACKET;
>         buffer[index++] = XHI_SYNC_PACKET;
>         buffer[index++] = XHI_NOOP_PACKET;
>  +       buffer[index++] = XHI_NOOP_PACKET;
>  +
>  +       /*
>  +        * Write the data to the FIFO and initiate the transfer of data present
>  +        * in the FIFO to the ICAP device.
>  +        */
>  +       status = drvdata->config->set_configuration(drvdata,
>  +                                                   &buffer[0], index);
>  +       if (status)
>  +               return status;
>  +
>  +       /* If the syncword was not found, then we need to start over. */
>  +       status = drvdata->config->get_status(drvdata);
>  +       if ((status & XHI_SR_DALIGN_MASK) != XHI_SR_DALIGN_MASK)
>  +               return -EIO;
>  +
>  +       index = 0;
>         buffer[index++] = hwicap_type_1_read(reg) | 1;
>         buffer[index++] = XHI_NOOP_PACKET;
>         buffer[index++] = XHI_NOOP_PACKET;
>  --
>  1.5.3.4-dirty
>
>
>
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-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.