System ACE driver - for 2.6 kernel - issue resolved

[agnel juni]

Hi Ameet,

We were able to get over with the unstability in the driver with the following fix in the code

Instead of fixing the number of sectors to be 2 in the loop, we are actually doing a read based on the kernel request  like this :

 for(i = xsa_cur_req->current_nr_sectors; i > 0; i-=xsa_cur_req->current_nr_sectors ){
                        xsa_device.req_done = 1;
                        while ((stat = cur_req(&SysAce, sector,
                                        xsa_cur_req->current_nr_sectors ,
                                        buffer)) == XST_DEVICE_BUSY)
                                xsa_short_delay();


Now the driver is stable with all the filesystem commands.

Please test this out and if appropriate patch this to the driver code.

Thanks
Junita

----- Original Message ----
From: Ameet Patil <ammubhai at gmail.com>
To: agnel juni <junijoseph at yahoo.co.in>
Cc: linuxppc-embedded at ozlabs.org
Sent: Thursday, 26 October, 2006 1:00:48 AM
Subject: Re: System ACE driver - for 2.6 kernel - need help to understand xsa_thread

Hi Junita,
    Its a hack really! When I was developing/porting the SysAce driver 
to 2.6 I tried to maintain the code as is from the 2.4 kernel driver. In 
doing so I found that there is a slight difference between the two 
kernels. i.e. I am not sure why, but the sysace device can only handle 
requests for 2 sectors at a time. This was fine in the 2.4 as the kernel 
always requested 2 sectors. However, in 2.6 I found that this is 
different: the requests are 8 secs. or more. I tried to fix this in vain 
by changing several parameters of the driver during initialization. 
Anyway, due to several issues I didn't try hard to fix it at that time.

Hence this hack: No matter how many sec. req. I get from the kernel, I 
use a loop to req. only 2 secs. at a time. The xsa_device.req_done is 
used as a flag and reset in the XSA IRQ IIRC.

If you find a better approach, please do update me. Hope this helps!

cheers,
-Ameet

agnel juni wrote:
> 
> Hello all
> 
> I am trying to understand the parameters that are sent through "cur_req" 
> function used in funtion xsa_thread in System ACE driver.
> 
> In xsa_thread function in the System ACE driver ,
> 
> In 2.4 kernel:
> --------------------
> while ((stat = cur_req(&SysAce, sector,
>                                        CURRENT->current_nr_sectors,
>                                        CURRENT->buffer)) == XST_DEVICE_BUSY)
>                         xsa_short_delay();
> 
>  
> Where as in 2.6 kernel this is changed to
> ---------------------------------------------------------------
> 
> for(i = xsa_cur_req->current_nr_sectors; i > 0; i-=2){
>                         xsa_device.req_done = 1;
>                         while ((stat = cur_req(&SysAce, sector,
>                                         2,
>                                         buffer)) == XST_DEVICE_BUSY)
>                                 xsa_short_delay();
> #endif
> 
> Ameet , could you help me understand the impact of the parameters, 
> especailly the 3rd paramter which is hardcoded in 2.6 kernel.It would be 
> great if you could clarify this in regard to 'mount' command.
> 
> Thanks in advance
> Junita
> 
> 
> 
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