From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthias Kaehlcke Subject: Re: [PATCH] tty: serial: qcom_geni_serial: Fix wrap around of TX buffer Date: Wed, 19 Dec 2018 11:04:25 -0800 Message-ID: <20181219190425.GC109358@google.com> References: <20181219181747.118278-1-mka@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Evan Green Cc: gregkh@linuxfoundation.org, jslaby@suse.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, msavaliy@codeaurora.org, ryandcase@chromium.org, Doug Anderson List-Id: linux-serial@vger.kernel.org On Wed, Dec 19, 2018 at 10:49:26AM -0800, Evan Green wrote: > On Wed, Dec 19, 2018 at 10:17 AM Matthias Kaehlcke wrote: > > > > Before commit a1fee899e5bed ("tty: serial: qcom_geni_serial: Fix > > softlock") the size of TX transfers was limited to the TX FIFO size, > > and wrap arounds of the UART circular buffer were split into two > > transfers. With the commit wrap around are allowed within a transfer. > > The TX FIFO of the geni serial port uses a word size of 4 bytes. In > > case of a circular buffer wrap within a transfer the driver currently > > may write an incomplete word to the FIFO, with some bytes containing > > data from the circular buffer and others being zero. Since the > > transfer isn't completed yet the zero bytes are sent as if they were > > actual data. > > > > Handle wrap arounds of the TX buffer properly and ensure that words > > written to the TX FIFO always contain valid data (unless the transfer > > is completed). > > > > Fixes: a1fee899e5bed ("tty: serial: qcom_geni_serial: Fix softlock") > > Signed-off-by: Matthias Kaehlcke > > Oh nice, so this did end up being your problem with corrupt > characters? Yes > Strange though, I still would have expected this bug to > result in inserted serial characters, rather than edited ones. You are right here, initially I interpreted that some bytes changed, but actually we observed inserted bytes, and later missing ones at the end of the transfer. > Either way, this looks good to me. > > Reviewed-by: Evan Green Thanks!