linux-kernel - Serial 8250 DMA Broken on OMAP3630

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Date:   Sun, 6 Oct 2019 12:04:47 -0500
From:   Adam Ford <aford173@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Vignesh R <vigneshr@...com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Douglas Anderson <dianders@...omium.org>,
        Adam Ford <aford173@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        Yegor Yefremov <yegorslists@...glemail.com>,
        linux-serial@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Serial 8250 DMA Broken on OMAP3630

Has anyone else had any issues using the CONFIG_SERIAL_8250_DMA on the OMAP?

I can use the DMA on the legacy, omap-serial driver, but when I enable
the DMA on the 8250-omap driver, I get missing frames in Bluetooth.

The older driver seems to have an ISR that seems to address a variety
of items compared to the very tiny ISR for 8250-omap.c.

I am not exactly sure where to start, but if someone has any
suggestions on how I can troubleshoot, please let me know.  As of now,
I have to disable CONFIG_SERIAL_8250_DMA to get the Bluetooth
connected to UART2 operational on a DM3730 at 3,000,000 baud, but it
appears to work just fine after some patches I just submitted for
handling RTS/CTS.  The legacy omap-serial driver works fine with DMA.

adam