On 11/04/2017 06:27 PM, Nik Nyby wrote:
In drivers/net/wireless/realtek/rtlwifi/rtl8821ae/hw.c, we have this function:
static u8 _rtl8821ae_dbi_read(struct rtl_priv *rtlpriv, u16 addr)
{
u16 read_addr = addr & 0xfffc;
u8 tmp = 0, count = 0, ret = 0;
rtl_write_word(rtlpriv, REG_DBI_ADDR, read_addr);
rtl_write_byte(rtlpriv, REG_DBI_FLAG, 0x2);
tmp = rtl_read_byte(rtlpriv, REG_DBI_FLAG);
count = 0;
while (tmp && count < 20) {
udelay(10);
tmp = rtl_read_byte(rtlpriv, REG_DBI_FLAG);
count++;
}
if (0 == tmp) {
read_addr = REG_DBI_RDATA + addr % 4;
ret = rtl_read_word(rtlpriv, read_addr);
}
return ret;
}
Near the end of the function, in this line:
ret = rtl_read_word(rtlpriv, read_addr);
rtl_read_word() returns a u16, but "ret" is declared as a u8. Is that a problem,
or is this code correct?
What's prompting this question is that I'm getting frequent disconnects from my
access point with my rtl8821ae device. I've experienced this behavior both
before and after the recent change to this function in commit
b8b8b16352cd90c6083033fd4487f04fae935c18.
If you read the commit message for commit b8b8b16352cd, you will find that we do
not understand why using a byte read causes failure, but reverting the change so
that it is a word read made it function again. The "fix" was found by a user
doing bisection, and verified on my system, where the RTL8821AE has stable
connections. The transfer rates take wild swings, but the connection is not dropped.
If you NIC behaves differently, then you will need to help us debug the problem.
If you had a kernel that worked, then you might try bisection. If that is not
possible, you might try various combinations of module parameters aspm,
int_clear, and msi. Those parameters default to 1, so setting one or more of
them to zero is the test. Note, however, that changing any of these might cause
the system to fail, thus I recommend that you test changes dynamically with
modprobe, and not create a file in /etc/modprobe.d/ until you have verified that
changing one or more of these parameters actually helps. That will keep from
making your system unbootable.
Larry
