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 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 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 = 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 -- View this message in context: http://www.nabble.com/Xilinx-Temac-Timer---tp16306218p16306218.html Sent from the linuxppc-embedded mailing list archive at Nabble.com. _______________________________________________ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded _______________________________________________ Linuxppc-embedded mailing list Linuxppc-embedded@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-embedded
