Xilin Temac Timer ?

Xilin Temac Timer ?

[khollan]

Hi

What is the purpose of stopping the timer in the ioctl call to read a PHY
register?  This is the code:

    case SIOCGMIIREG:   /* Read GMII PHY register. */
    case SIOCDEVPRIVATE + 1:    /* for binary compat, remove in 2.5 */
        if (data->phy_id > 31 || data->reg_num > 31)
            return -ENXIO;

        /* Stop the PHY timer to prevent reentrancy. */
        spin_lock_irqsave(&XTE_spinlock, flags);
        del_timer_sync(&lp->phy_timer);

        ret = XTemac_PhyRead(&lp->Emac, data->phy_id,
                       data->reg_num, &data->val_out);

        /* Start the PHY timer up again. */
        lp->phy_timer.expires = jiffies + 2 * HZ;
        add_timer(&lp->phy_timer);
        spin_unlock_irqrestore(&XTE_spinlock, flags);
        if (ret != XST_SUCCESS) {
            printk(KERN_ERR
                   "%s: XTemac: could not read from PHY, error=%d.\n",
                   dev->name, ret);
            return -EBUSY;
        }
        return 0;

I ask because I have an application that needs to read a Phy register before
the timer has started to see if a link is present.  This causes a kernel bug
when trying to run the del_timer_sync function because there is not a
running timer.  I would like to know if it is safe to remove the timer del
and add but keep the spin lock.

Thanks for your help

Kevin
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RE: Xilinx Temac Timer ?

[John Linn]

Hi Kevin,

I didn't write the code but I know the driver somewhat.

I think the intention of stopping the timer is to prevent the reentrancy
as the comment says because there is a function, gmii_poll, that is
setup on the timer to go read the phy registers to see if anything
changed in the phy.=20

Stopping the timer prevents a phy read from happening in gmii_poll in
the middle of the ioctl phy read which could hose things up.

I don't see why you couldn't change that timer stop to some other form
of synchronization/mutual exclusion so that the phy reads don't collide.

As I look at it, it appears to me the spinlock should provide the
synchronization needed without stopping the timer, but maybe I'm missing
something. I CCed John Bonesio as he's the guy that developed this code
I believe and maybe he'll have more insight here.

Thanks,
John

-----Original Message-----
From: linuxppc-embedded-bounces+john.linn=3Dxilinx.com@ozlabs.org
[mailto:linuxppc-embedded-bounces+john.linn=3Dxilinx.com@ozlabs.org] On
Behalf Of khollan
Sent: Wednesday, March 26, 2008 11:03 AM
To: linuxppc-embedded@ozlabs.org
Subject: Xilinx Temac Timer ?


Hi

What is the purpose of stopping the timer in the ioctl call to read a
PHY
register?  This is the code:

    case SIOCGMIIREG:   /* Read GMII PHY register. */
    case SIOCDEVPRIVATE + 1:    /* for binary compat, remove in 2.5 */
        if (data->phy_id > 31 || data->reg_num > 31)
            return -ENXIO;

        /* Stop the PHY timer to prevent reentrancy. */
        spin_lock_irqsave(&XTE_spinlock, flags);
        del_timer_sync(&lp->phy_timer);

        ret =3D XTemac_PhyRead(&lp->Emac, data->phy_id,
                       data->reg_num, &data->val_out);

        /* Start the PHY timer up again. */
        lp->phy_timer.expires =3D jiffies + 2 * HZ;
        add_timer(&lp->phy_timer);
        spin_unlock_irqrestore(&XTE_spinlock, flags);
        if (ret !=3D XST_SUCCESS) {
            printk(KERN_ERR
                   "%s: XTemac: could not read from PHY, error=3D%d.\n",
                   dev->name, ret);
            return -EBUSY;
        }
        return 0;

I ask because I have an application that needs to read a Phy register
before
the timer has started to see if a link is present.  This causes a kernel
bug
when trying to run the del_timer_sync function because there is not a
running timer.  I would like to know if it is safe to remove the timer
del
and add but keep the spin lock.

Thanks for your help

Kevin
--=20
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http://www.nabble.com/Xilinx-Temac-Timer---tp16306218p16306218.html
Sent from the linuxppc-embedded mailing list archive at Nabble.com.

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RE: Xilinx Temac Timer ?

[khollan]

John Linn wrote:
> 
> Hi Kevin,
> 
> I didn't write the code but I know the driver somewhat.
> 
> I think the intention of stopping the timer is to prevent the reentrancy
> as the comment says because there is a function, gmii_poll, that is
> setup on the timer to go read the phy registers to see if anything
> changed in the phy. 
> 
> Stopping the timer prevents a phy read from happening in gmii_poll in
> the middle of the ioctl phy read which could hose things up.
> 
> I don't see why you couldn't change that timer stop to some other form
> of synchronization/mutual exclusion so that the phy reads don't collide.
> 
> As I look at it, it appears to me the spinlock should provide the
> synchronization needed without stopping the timer, but maybe I'm missing
> something. I CCed John Bonesio as he's the guy that developed this code
> I believe and maybe he'll have more insight here.
> 
> Thanks,
> John
> 
I removed the timer code, and it seems to be working correctly, hopefully
the spin lock is all I need to lock out the polling function.  Thanks for
you help

Kevin
-- 
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JFFS2 root-fs

[Georg Schardt]

Hi all,


i ask this questions a few months ago but i still have no solution for 
my problem :(

i try to boot linux with a root-fs from flash. i create a jffs2-image, 
download it to flash and
the u-boot "ls" shows me all my files, so i think all is right with the 
image.


BUT, the kernel hangs after mounting the rootfs:

[    0.572527] physmap platform flash device: 00400000 at 04000000
[    0.579205] physmap-flash.0: Found 1 x16 devices at 0x0 in 16-bit bank
[    0.586062]  Amd/Fujitsu Extended Query Table at 0x0041
[    0.591456] number of CFI chips: 1
[    0.594973] cfi_cmdset_0002: Disabling erase-suspend-program due to 
code brokenness.
[    0.602916] 4 cmdlinepart partitions found on MTD device physmap-flash.0
[    0.609759] Creating 4 MTD partitions on "physmap-flash.0":
[    0.615454] 0x00000000-0x00010000 : "env"
[    0.619599] mtd: Giving out device 0 to env
[    0.628166] 0x00010000-0x00030000 : "uboot"
[    0.632563] mtd: Giving out device 1 to uboot
[    0.641172] 0x00030000-0x00160000 : "kernel"
[    0.645744] mtd: Giving out device 2 to kernel
[    0.654372] 0x00160000-0x00400000 : "fs"
[    0.658604] mtd: Giving out device 3 to fs
[    0.666992] block2mtd: version $Revision: 1.30 $
[    0.673341] mice: PS/2 mouse device common for all mice
[    0.679193] TCP cubic registered
[    0.683016] NET: Registered protocol family 1
[    0.687619] NET: Registered protocol family 17
[    0.696556] MTDSB: dev_name "/dev/root"
[    0.700723] MTDSB: path_lookup() returned 0, inode c02ec290
[    0.706515] MTDSB: New superblock for device 3 ("fs")
[    2.386543] VFS: Mounted root (jffs2 filesystem).
[    2.392022] Freeing unused kernel memory: 76k init
[    2.397182] Warning: unable to open an initial console.
[    2.416877] Kernel panic - not syncing: No init found.  Try passing 
init= option to kernel.
[    2.427312] Rebooting in 180 seconds..


It seems to me, that the kernel does not find ANY file. because the 
/dev/console file is in the image, but the initial console is not found too

any ideas and hints are appreciated
regars
georg



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