[v2,1/1] net: fec: ptp: avoid register access when ipg clock is disabled

When accessing the timecounter register on an i.MX8MQ the kernel hangs.
This is only the case when the interface is down. This can be reproduced
by reading with 'phc_ctrl eth0 get'.

Like described in the change in 91c0d987a9788dcc5fe26baafd73bf9242b68900
the igp clock is disabled when the interface is down and leads to a
system hang.

So we check if the ptp clock status before reading the timecounter
register.

Signed-off-by: Heiko Thiery <heiko.thiery@gmail.com>
---
v2:
 - add mutex (thanks to Richard)

 drivers/net/ethernet/freescale/fec_ptp.c | 6 ++++++
 1 file changed, 6 insertions(+)

Hi Heiko,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on net/master]
[also build test ERROR on net-next/master ipvs/master linus/master v5.11 next-20210225]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Heiko-Thiery/net-fec-ptp-avoid-register-access-when-ipg-clock-is-disabled/20210226-050218
base:   https://git.kernel.org/pub/scm/linux/kernel/git/davem/net.git 6cf739131a15e4177e58a1b4f2bede9d5da78552
config: mips-randconfig-r013-20210225 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project a921aaf789912d981cbb2036bdc91ad7289e1523)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install mips cross compiling tool for clang build
        # apt-get install binutils-mips-linux-gnu
        # https://github.com/0day-ci/linux/commit/a7258bb15d947bb808b6209012a56ae993ec6001
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Heiko-Thiery/net-fec-ptp-avoid-register-access-when-ipg-clock-is-disabled/20210226-050218
        git checkout a7258bb15d947bb808b6209012a56ae993ec6001
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=mips 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All error/warnings (new ones prefixed by >>):

>> drivers/net/ethernet/freescale/fec_ptp.c:380:14: error: use of undeclared identifier 'fep'
           mutex_lock(&fep->ptp_clk_mutex);
                       ^
   drivers/net/ethernet/freescale/fec_ptp.c:383:17: error: use of undeclared identifier 'fep'
                   mutex_unlock(&fep->ptp_clk_mutex);
                                 ^
>> drivers/net/ethernet/freescale/fec_ptp.c:384:3: warning: misleading indentation; statement is not part of the previous 'if' [-Wmisleading-indentation]
                   return -EINVAL;
                   ^
   drivers/net/ethernet/freescale/fec_ptp.c:382:2: note: previous statement is here
           if (!adapter->ptp_clk_on)
           ^
   drivers/net/ethernet/freescale/fec_ptp.c:388:16: error: use of undeclared identifier 'fep'
           mutex_unlock(&fep->ptp_clk_mutex);
                         ^
   1 warning and 3 errors generated.


vim +/fep +380 drivers/net/ethernet/freescale/fec_ptp.c

   364	
   365	/**
   366	 * fec_ptp_gettime
   367	 * @ptp: the ptp clock structure
   368	 * @ts: timespec structure to hold the current time value
   369	 *
   370	 * read the timecounter and return the correct value on ns,
   371	 * after converting it into a struct timespec.
   372	 */
   373	static int fec_ptp_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
   374	{
   375		struct fec_enet_private *adapter =
   376		    container_of(ptp, struct fec_enet_private, ptp_caps);
   377		u64 ns;
   378		unsigned long flags;
   379	
 > 380		mutex_lock(&fep->ptp_clk_mutex);
   381		/* Check the ptp clock */
   382		if (!adapter->ptp_clk_on)
   383			mutex_unlock(&fep->ptp_clk_mutex);
 > 384			return -EINVAL;
   385		spin_lock_irqsave(&adapter->tmreg_lock, flags);
   386		ns = timecounter_read(&adapter->tc);
   387		spin_unlock_irqrestore(&adapter->tmreg_lock, flags);
   388		mutex_unlock(&fep->ptp_clk_mutex);
   389	
   390		*ts = ns_to_timespec64(ns);
   391	
   392		return 0;
   393	}
   394	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org