ede5a38985
When the MAC is connected to a 10 Mb/s PHY and the PTP clock is derived from the MAC reference clock (default), the clk_ptp_rate becomes too small and the calculated sub second increment becomes 0 when computed by the stmmac_config_sub_second_increment() function within stmmac_init_tstamp_counter(). Therefore, the subsequent div_u64 in stmmac_init_tstamp_counter() operation triggers a divide by 0 exception as shown below. [ 95.062067] socfpga-dwmac ff700000.ethernet eth0: Register MEM_TYPE_PAGE_POOL RxQ-0 [ 95.076440] socfpga-dwmac ff700000.ethernet eth0: PHY [stmmac-0:08] driver [NCN26000] (irq=49) [ 95.095964] dwmac1000: Master AXI performs any burst length [ 95.101588] socfpga-dwmac ff700000.ethernet eth0: No Safety Features support found [ 95.109428] Division by zero in kernel. [ 95.113447] CPU: 0 PID: 239 Comm: ifconfig Not tainted 6.1.0-rc7-centurion3-1.0.3.0-01574-gb624218205b7-dirty #77 [ 95.123686] Hardware name: Altera SOCFPGA [ 95.127695] unwind_backtrace from show_stack+0x10/0x14 [ 95.132938] show_stack from dump_stack_lvl+0x40/0x4c [ 95.137992] dump_stack_lvl from Ldiv0+0x8/0x10 [ 95.142527] Ldiv0 from __aeabi_uidivmod+0x8/0x18 [ 95.147232] __aeabi_uidivmod from div_u64_rem+0x1c/0x40 [ 95.152552] div_u64_rem from stmmac_init_tstamp_counter+0xd0/0x164 [ 95.158826] stmmac_init_tstamp_counter from stmmac_hw_setup+0x430/0xf00 [ 95.165533] stmmac_hw_setup from __stmmac_open+0x214/0x2d4 [ 95.171117] __stmmac_open from stmmac_open+0x30/0x44 [ 95.176182] stmmac_open from __dev_open+0x11c/0x134 [ 95.181172] __dev_open from __dev_change_flags+0x168/0x17c [ 95.186750] __dev_change_flags from dev_change_flags+0x14/0x50 [ 95.192662] dev_change_flags from devinet_ioctl+0x2b4/0x604 [ 95.198321] devinet_ioctl from inet_ioctl+0x1ec/0x214 [ 95.203462] inet_ioctl from sock_ioctl+0x14c/0x3c4 [ 95.208354] sock_ioctl from vfs_ioctl+0x20/0x38 [ 95.212984] vfs_ioctl from sys_ioctl+0x250/0x844 [ 95.217691] sys_ioctl from ret_fast_syscall+0x0/0x4c [ 95.222743] Exception stack(0xd0ee1fa8 to 0xd0ee1ff0) [ 95.227790] 1fa0: 00574c4f be9aeca4 00000003 00008914 be9aeca4 be9aec50 [ 95.235945] 1fc0: 00574c4f be9aeca4 0059f078 00000036 be9aee8c be9aef7a 00000015 00000000 [ 95.244096] 1fe0: 005a01f0 be9aec38 004d7484 b6e67d74 Signed-off-by: Piergiorgio Beruto <piergiorgio.beruto@gmail.com> Fixes: 91a2559c1dc5 ("net: stmmac: Fix sub-second increment") Reviewed-by: Andrew Lunn <andrew@lunn.ch> Link: https://lore.kernel.org/r/de4c64ccac9084952c56a06a8171d738604c4770.1670678513.git.piergiorgio.beruto@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.