bus: ti-sysc: Flush posted write on enable before reset

[ Upstream commit 34539b442b3bc7d5bf10164750302b60b91f18a7 ]

The am335x devices started producing boot errors for resetting musb module
in because of subtle timing changes:

Unhandled fault: external abort on non-linefetch (0x1008)
...
sysc_poll_reset_sysconfig from sysc_reset+0x109/0x12
sysc_reset from sysc_probe+0xa99/0xeb0
...

The fix is to flush posted write after enable before reset during
probe. Note that some devices also need to specify the delay after enable
with ti,sysc-delay-us, but this is not needed for musb on am335x based on
my tests.

Reported-by: kernelci.org bot <bot@kernelci.org>
Closes: https://storage.kernelci.org/next/master/next-20230614/arm/multi_v7_defconfig+CONFIG_THUMB2_KERNEL=y/gcc-10/lab-cip/baseline-beaglebone-black.html
Fixes: 596e7955692b ("bus: ti-sysc: Add support for software reset")
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/bus/ti-sysc.c b/drivers/bus/ti-sysc.c
index cae078bffc7156c81c374d2c671709d4bd63266c..9b7268bae66ab836a1098e7e14609ed323150214 100644 (file)
--- a/drivers/bus/ti-sysc.c
+++ b/drivers/bus/ti-sysc.c
@@ -2159,6 +2159,8 @@ static int sysc_reset(struct sysc *ddata)
                sysc_val = sysc_read_sysconfig(ddata);
                sysc_val |= sysc_mask;
                sysc_write(ddata, sysc_offset, sysc_val);
+               /* Flush posted write */
+               sysc_val = sysc_read_sysconfig(ddata);
        }
 
        if (ddata->cfg.srst_udelay)