From 529ba0d9669386157457a1cb96294d2fe79b3f88 Mon Sep 17 00:00:00 2001 From: David Brownell Date: Tue, 30 Jun 2009 11:41:30 -0700 Subject: [PATCH] spi: bitbang bugfix in message setup Bugfix to spi_bitbang infrastructure: make sure to always set transfer parameters on the first pass through the message's per-transfer loop. This can matter with drivers that replace the per-word or per-buffer transfer primitives, on busses with multiple SPI devices. Previously, this could have started messages using the settings left after previous messages. The problem was observed when a high speed chip (m25p80 type flash) was running very slowly because a low speed device (avr8 microcontroller) had previously used the bus. Similar faults could have driven the low speed device too fast, or used an unexpected word size. Acked-by: Steven A. Falco Signed-off-by: David Brownell Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/spi/spi_bitbang.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/drivers/spi/spi_bitbang.c b/drivers/spi/spi_bitbang.c index 2a5abc08e85..f1db395dd88 100644 --- a/drivers/spi/spi_bitbang.c +++ b/drivers/spi/spi_bitbang.c @@ -258,6 +258,11 @@ static void bitbang_work(struct work_struct *work) struct spi_bitbang *bitbang = container_of(work, struct spi_bitbang, work); unsigned long flags; + int do_setup = -1; + int (*setup_transfer)(struct spi_device *, + struct spi_transfer *); + + setup_transfer = bitbang->setup_transfer; spin_lock_irqsave(&bitbang->lock, flags); bitbang->busy = 1; @@ -269,8 +274,6 @@ static void bitbang_work(struct work_struct *work) unsigned tmp; unsigned cs_change; int status; - int (*setup_transfer)(struct spi_device *, - struct spi_transfer *); m = container_of(bitbang->queue.next, struct spi_message, queue); @@ -287,19 +290,19 @@ static void bitbang_work(struct work_struct *work) tmp = 0; cs_change = 1; status = 0; - setup_transfer = NULL; list_for_each_entry (t, &m->transfers, transfer_list) { - /* override or restore speed and wordsize */ - if (t->speed_hz || t->bits_per_word) { - setup_transfer = bitbang->setup_transfer; + /* override speed or wordsize? */ + if (t->speed_hz || t->bits_per_word) + do_setup = 1; + + /* init (-1) or override (1) transfer params */ + if (do_setup != 0) { if (!setup_transfer) { status = -ENOPROTOOPT; break; } - } - if (setup_transfer) { status = setup_transfer(spi, t); if (status < 0) break; @@ -363,9 +366,10 @@ static void bitbang_work(struct work_struct *work) m->status = status; m->complete(m->context); - /* restore speed and wordsize */ - if (setup_transfer) + /* restore speed and wordsize if it was overridden */ + if (do_setup == 1) setup_transfer(spi, NULL); + do_setup = 0; /* normally deactivate chipselect ... unless no error and * cs_change has hinted that the next message will probably -- 2.32.0.93.g670b81a890