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* [PATCH] spi/omap2_mcspi: disable and enable chan between each SPI transfer
@ 2010-06-24 12:12 ` Jason Wang
  0 siblings, 0 replies; 36+ messages in thread
From: Jason Wang @ 2010-06-24 12:12 UTC (permalink / raw)
  To: grant.likely, roman.tereshonkov, david-b
  Cc: spi-devel-general, linux-arm-kernel

In current design, the SPI channel is always enable during the period
of handling a SPI message, it is risky when more than one SPI transfer
are included in a message. Current working route like that:
[
  SPI channel enable
  configure channel
  handle transfer #1
  configure channel
  handle transfer #2
  ...
  SPI channel disable
]
If we can disable channel before configure it and reenable
channel after it is configured, it will be more safe.

The commit a330ce2 "omap2_mcspi: Flush posted writes" make this risk
to a real problem for ads7846 driver on omap3530evm. The
ads7846 driver will send a SPI messge which includes,
[
  TX_ONLY transfer (1 byte)
  RX_ONLY transfer (2 bytes)
  TX_ONLY transfer (1 byte)
  RX_ONLY transfer (2 bytes)
]
If we don't add disable/reenable channel between TX and RX transfers,
the RX transfer will get wrong datas sent from slave.

Signed-off-by: Jason Wang <jason77.wang@gmail.com>
---
 drivers/spi/omap2_mcspi.c |   16 ++++++----------
 1 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
index b3a94ca..1e3cb7b 100644
--- a/drivers/spi/omap2_mcspi.c
+++ b/drivers/spi/omap2_mcspi.c
@@ -408,7 +408,6 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
 				count -= (word_len <= 8)  ? 2 :
 					(word_len <= 16) ? 4 :
 					/* word_len <= 32 */ 8;
-				omap2_mcspi_set_enable(spi, 1);
 				return count;
 			}
 		}
@@ -430,8 +429,10 @@ omap2_mcspi_txrx_dma(struct spi_device *spi, struct spi_transfer *xfer)
 				 (word_len <= 16) ? 2 :
 			       /* word_len <= 32 */ 4;
 		}
-		omap2_mcspi_set_enable(spi, 1);
 	}
+
+	omap2_mcspi_set_enable(spi, 0);
+
 	return count;
 }
 
@@ -517,8 +518,6 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 						goto out;
 					}
 					c = 0;
-				} else if (c == 0 && tx == NULL) {
-					omap2_mcspi_set_enable(spi, 0);
 				}
 
 				*rx++ = __raw_readl(rx_reg);
@@ -570,8 +569,6 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 						goto out;
 					}
 					c = 0;
-				} else if (c == 0 && tx == NULL) {
-					omap2_mcspi_set_enable(spi, 0);
 				}
 
 				*rx++ = __raw_readl(rx_reg);
@@ -623,8 +620,6 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 						goto out;
 					}
 					c = 0;
-				} else if (c == 0 && tx == NULL) {
-					omap2_mcspi_set_enable(spi, 0);
 				}
 
 				*rx++ = __raw_readl(rx_reg);
@@ -646,7 +641,7 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 			dev_err(&spi->dev, "EOT timed out\n");
 	}
 out:
-	omap2_mcspi_set_enable(spi, 1);
+	omap2_mcspi_set_enable(spi, 0);
 	return count - c;
 }
 
@@ -894,7 +889,6 @@ static void omap2_mcspi_work(struct work_struct *work)
 		cs = spi->controller_state;
 		cd = spi->controller_data;
 
-		omap2_mcspi_set_enable(spi, 1);
 		list_for_each_entry(t, &m->transfers, transfer_list) {
 			if (t->tx_buf == NULL && t->rx_buf == NULL && t->len) {
 				status = -EINVAL;
@@ -931,6 +925,8 @@ static void omap2_mcspi_work(struct work_struct *work)
 
 			mcspi_write_chconf0(spi, chconf);
 
+			omap2_mcspi_set_enable(spi, 1);
+
 			if (t->len) {
 				unsigned	count;
 
-- 
1.5.6.5

^ permalink raw reply related	[flat|nested] 36+ messages in thread

end of thread, other threads:[~2010-07-13 23:48 UTC | newest]

Thread overview: 36+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-06-24 12:12 [PATCH] spi/omap2_mcspi: disable and enable chan between each SPI transfer Jason Wang
2010-06-24 12:12 ` Jason Wang
     [not found] ` <1277381565-6305-1-git-send-email-jason77.wang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2010-06-24 14:32   ` roman.tereshonkov-xNZwKgViW5gAvxtiuMwx3w
2010-06-24 14:32     ` roman.tereshonkov at nokia.com
     [not found]     ` <E1C7579D1379824DAE67858071C810382DD83846FB-xJW1crHCIS+8kqYwC468Frtp2NbXvJi8gfoxzgwHRXE@public.gmane.org>
2010-06-25 12:05       ` jason
2010-06-25 12:05         ` jason
2010-06-27  6:08         ` Grant Likely
2010-06-27  6:08           ` Grant Likely
     [not found]           ` <AANLkTinO3kndb9bIAGlz4-h2TW64NGthHBRcVlE3gqun-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2010-06-27 13:12             ` jason
2010-06-27 13:12               ` jason
2010-06-24 15:12   ` Grant Likely
2010-06-24 15:12     ` Grant Likely
2010-06-25 12:30     ` jason
2010-06-25 12:30       ` jason
     [not found]       ` <4C24A182.4060009-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2010-06-28  9:12         ` roman.tereshonkov-xNZwKgViW5gAvxtiuMwx3w
2010-06-28  9:12           ` roman.tereshonkov at nokia.com
     [not found]           ` <E1C7579D1379824DAE67858071C810382DD8495B26-xJW1crHCIS+8kqYwC468Frtp2NbXvJi8gfoxzgwHRXE@public.gmane.org>
2010-06-28 12:59             ` jason
2010-06-28 12:59               ` jason
2010-06-29 10:20               ` roman.tereshonkov
2010-06-29 10:20                 ` roman.tereshonkov at nokia.com
     [not found]                 ` <E1C7579D1379824DAE67858071C810382DD84963BC-xJW1crHCIS+8kqYwC468Frtp2NbXvJi8gfoxzgwHRXE@public.gmane.org>
2010-06-29 13:17                   ` jason
2010-06-29 13:17                     ` jason
2010-07-01 11:58                   ` jason
2010-07-01 11:58                     ` jason
     [not found]                     ` <4C2C82E9.2010103-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2010-07-01 13:57                       ` roman.tereshonkov-xNZwKgViW5gAvxtiuMwx3w
2010-07-01 13:57                         ` roman.tereshonkov at nokia.com
     [not found]                         ` <E1C7579D1379824DAE67858071C810382DD859571A-xJW1crHCIS+8kqYwC468Frtp2NbXvJi8gfoxzgwHRXE@public.gmane.org>
2010-07-01 23:35                           ` jason
2010-07-01 23:35                             ` jason
2010-07-03 11:21                           ` jason
2010-07-03 11:21                             ` jason
2010-07-13 13:26                           ` jason
2010-07-13 13:26                             ` jason
     [not found]                             ` <4C3C6971.5010004-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2010-07-13 18:09                               ` roman.tereshonkov-xNZwKgViW5gAvxtiuMwx3w
2010-07-13 18:09                                 ` roman.tereshonkov at nokia.com
     [not found]                                 ` <E1C7579D1379824DAE67858071C810382DD8772AB3-xJW1crHCIS+8kqYwC468Frtp2NbXvJi8gfoxzgwHRXE@public.gmane.org>
2010-07-13 23:48                                   ` jason
2010-07-13 23:48                                     ` jason

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