From: Yun Zhou <yun.zhou@windriver.com>
To: <broonie@kernel.org>, <yun.zhou@windriver.com>
Cc: <linux-spi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<ying.xue@windriver.com>
Subject: [PATCH] spi: disable chipselect after complete transfer
Date: Wed, 9 Feb 2022 18:00:42 +0800 [thread overview]
Message-ID: <20220209100042.22941-1-yun.zhou@windriver.com> (raw)
If there are 2 slaves or more on a spi bus, e.g. A and B, we processed a
transfer to A, the CS will be selected for A whose 'last_cs_enable' will
be recorded to true at the same time. Then we processed a transfer to B,
the CS will be switched to B. And then if we transmit data to A again, it
will not enable CS back to A because 'last_cs_enable' is true.
In addition, if CS is not disabled, Some controllers in automatic
transmission state will receive unpredictable data, such as Cadence SPI
controller.
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
---
drivers/spi/spi.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index fdd530b150a7..ebbba0b08186 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1417,7 +1417,6 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
struct spi_message *msg)
{
struct spi_transfer *xfer;
- bool keep_cs = false;
int ret = 0;
struct spi_statistics *statm = &ctlr->statistics;
struct spi_statistics *stats = &msg->spi->statistics;
@@ -1486,10 +1485,8 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
spi_transfer_delay_exec(xfer);
if (xfer->cs_change) {
- if (list_is_last(&xfer->transfer_list,
+ if (!list_is_last(&xfer->transfer_list,
&msg->transfers)) {
- keep_cs = true;
- } else {
spi_set_cs(msg->spi, false, false);
_spi_transfer_cs_change_delay(msg, xfer);
spi_set_cs(msg->spi, true, false);
@@ -1500,8 +1497,7 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
}
out:
- if (ret != 0 || !keep_cs)
- spi_set_cs(msg->spi, false, false);
+ spi_set_cs(msg->spi, false, false);
if (msg->status == -EINPROGRESS)
msg->status = ret;
--
2.26.1
next reply other threads:[~2022-02-09 12:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-09 10:00 Yun Zhou [this message]
2022-02-09 13:40 ` [PATCH] spi: disable chipselect after complete transfer Mark Brown
2022-02-10 2:03 ` Yun Zhou
2022-02-10 11:18 ` Mark Brown
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