serial: sc16is7xx: fix TX fifo corruption

Browse source

Sometimes, when a packet is received on channel A at almost the same time
as a packet is about to be transmitted on channel B, we observe with a
logic analyzer that the received packet on channel A is transmitted on
channel B. In other words, the Tx buffer data on channel B is corrupted
with data from channel A.

The problem appeared since commit 4409df5866 ("serial: sc16is7xx: change
EFR lock to operate on each channels"), which changed the EFR locking to
operate on each channel instead of chip-wise.

This commit has introduced a regression, because the EFR lock is used not
only to protect the EFR registers access, but also, in a very obscure and
undocumented way, to protect access to the data buffer, which is shared by
the Tx and Rx handlers, but also by each channel of the IC.

Fix this regression first by switching to kfifo_out_linear_ptr() in
sc16is7xx_handle_tx() to eliminate the need for a shared Rx/Tx buffer.

Secondly, replace the chip-wise Rx buffer with a separate Rx buffer for
each channel.

Fixes: 4409df5866 ("serial: sc16is7xx: change EFR lock to operate on each channels")
Cc: stable@vger.kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20240723125302.1305372-2-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Hugo Villeneuve 2024-07-23 08:53:00 -04:00 • committed by Greg Kroah-Hartman

parent 6eabce6608

commit 133f4c00b8

1 changed files with 11 additions and 10 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

21

drivers/tty/serial/sc16is7xx.c

View file