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authorPaul Fulghum <paulkf@microgate.com>2009-12-09 12:31:39 -0800
committerGreg Kroah-Hartman <gregkh@suse.de>2010-03-02 14:43:08 -0800
commitde538eb3441e8b9f7aedb3a37e46c005538451dc (patch)
treef8d6418b04ff4049c4864c7a554b57e2a006f456 /drivers/parport
parent8fe2d54145a51238308d333f9dc57c5df575ff78 (diff)
downloadlinux-de538eb3441e8b9f7aedb3a37e46c005538451dc.tar.bz2
serial: synclink_gt: dropped transmit data bugfix
Fix transmit bug that could drop send data if write() called close to serial transmitter going idle after sending previous data. Bug is caused by incorrect use of device information member tx_count. Driver originally processed one data block (write call) at a time, waiting for transmit idle before sending more. tx_count recorded how much data was loaded in DMA buffers on write(), and was cleared on send completion. tx_count use was overloaded to record accumulated data from put_char() callback when transmitter was idle. A bug was introduced when transmit code was reworked to allow multiple blocks of data in the tx DMA buffers which keeps transmitter from going idle between blocks. tx_count was set to size of last block loaded, cleared when tx went idle, and monitored to know when to restart transmitter without proper synchronization. tx_count could be cleared when unsent data remained in DMA buffers and transmitter required restarting, effectively dropping unsent data. Solution: 1. tx_count now used only to track accumulated data from put_char 2. DMA buffer state tracked by direct inspection of descriptors with spinlock synchronization 3. consolidate these tasks in tx_load() : a. check for available buffer space b. load buffers c. restart DMA and or serial transmitter as needed These steps were previously duplicated in multiple places, sometimes incompletely. 4. fix use of tx_count as active transmit indicator, instead using tx_active which is meant for that purpose Signed-off-by: Paul Fulghum <paulkf@microgate.com> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/parport')
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