Re: [PATCH net-next v3 1/6] net: phy: mscc: migrate to phy_select/restore_page functions
From: Andreas Schwab <hidden>
Date: 2018-11-19 14:57:21
On Okt 08 2018, Quentin Schulz [off-list ref] wrote:
The Microsemi PHYs have multiple banks of registers (called pages). Registers can only be accessed from one page, if we need a register from another page, we need to switch the page and the registers of all other pages are not accessible anymore. Basically, to read register 5 from page 0, 1, 2, etc., you do the same phy_read(phydev, 5); but you need to set the desired page beforehand. In order to guarantee that two concurrent functions do not change the page, we need to do some locking per page. This can be achieved with the use of phy_select_page and phy_restore_page functions but phy_write/read calls in-between those two functions shall be replaced by their lock-free alternative __phy_write/read. Let's migrate this driver to those functions.
This has some serious locking problem. [<0>] __schedule+0x25e/0x74c [<0>] schedule+0x1a/0x58 [<0>] schedule_preempt_disabled+0xc/0x14 [<0>] __mutex_lock.isra.0+0x10e/0x22e [<0>] __mutex_lock_slowpath+0xe/0x16 [<0>] mutex_lock+0x22/0x2a [<0>] mdiobus_read+0x36/0x60 [<0>] vsc85xx_config_init+0x4c/0x1e2 [<0>] phy_init_hw+0x3c/0x52 [<0>] phy_attach_direct+0xec/0x1dc [<0>] phy_connect_direct+0x1a/0x56 [<0>] macb_probe+0x800/0xb5e [macb] [<0>] platform_drv_probe+0x3e/0x7e [<0>] really_probe+0xba/0x310 [<0>] driver_probe_device+0x54/0xf2 [<0>] __driver_attach+0xde/0x106 [<0>] bus_for_each_dev+0x4a/0x72 [<0>] driver_attach+0x1a/0x22 [<0>] bus_add_driver+0x1ce/0x212 [<0>] driver_register+0x3a/0xd0 [<0>] __platform_driver_register+0x3a/0x42 [<0>] macb_driver_init+0x20/0x28 [macb] [<0>] do_one_initcall+0x48/0x128 [<0>] do_init_module+0x4a/0x186 [<0>] load_module+0xd6a/0xe6a [<0>] sys_finit_module+0xc6/0xfc [<0>] check_syscall_nr+0x22/0x22 Andreas. -- Andreas Schwab, SUSE Labs, schwab@suse.de GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7 "And now for something completely different."