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Fix nasty race condition

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git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@1050 42af7a65-404d-4744-a932-0658087f49c3
This commit is contained in:
patacongo 2008-10-15 22:53:34 +00:00
parent 2c1bfb4b8b
commit 856ef35532
1 changed files with 25 additions and 8 deletions
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33
configs/mcu123-lpc214x/src/up_spi.c
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@ -66,6 +66,7 @@
#include <nuttx/spi.h>
#include <arch/board/board.h>
#include <nuttx/arch.h>
#include <nuttx/spi.h>
#include "up_internal.h"
@ -271,6 +272,8 @@ ubyte spi_sndbyte(FAR struct spi_dev_s *dev, ubyte ch)
void spi_sndblock(FAR struct spi_dev_s *dev, FAR const ubyte *buffer, size_t buflen)
{
ubyte sr;
/* Loop while thre are bytes remaining to be sent */
while (buflen > 0)
@ -287,18 +290,32 @@ void spi_sndblock(FAR struct spi_dev_s *dev, FAR const ubyte *buffer, size_t buf
}
}
/* Then read from the RX FIFO while the RX FIFO is not empty or the TX FIFO
* is not empty. We should get the same number of bytes in response as were
* sent.
*/
/* Then discard all card responses until the TX FIFO is emptied. */
while ((getreg8(LPC214X_SPI1_SR) & LPC214X_SPI1SR_RNE) ||
!(getreg8(LPC214X_SPI1_SR) & LPC214X_SPI1SR_TFE))
do
{
/* Read and discard */
/* Is there anything in the RX fifo? */
(void)getreg16(LPC214X_SPI1_DR);
sr = getreg8(LPC214X_SPI1_SR);
if ((sr & LPC214X_SPI1SR_RNE) != 0)
{
/* Yes.. Read and discard */
(void)getreg16(LPC214X_SPI1_DR);
}
/* There is a race condition where TFE may go FALSE just before
* RNE goes true. The nasty little delay in the following solves
* that (it could probably be tuned to improve performance).
*/
else if ((sr & LPC214X_SPI1SR_TFE) == 0)
{
up_udelay(200);
sr = getreg8(LPC214X_SPI1_SR);
}
}
while ((sr & LPC214X_SPI1SR_RNE) != 0 || (sr & LPC214X_SPI1SR_TFE) == 0);
}
/****************************************************************************