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drivers: dma_qmsi: Wait few cycles to allow DMA controller changes

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Add few nop instructions to allow the DMA controller settle,
It takes time after starting the transfer to access the DMA
controller registers, so a few cycles are added, the minimal number
of cycles needed has been calculated using tests results on c1000
development board.

Jira: ZEP-1803

Change-Id: I1f8e8478f0350e1b6e4dd596b783dc4babc2d02b
Signed-off-by: Sergio Rodriguez <sergio.sf.rodriguez@intel.com>
This commit is contained in:
Sergio Rodriguez 2017-03-07 14:38:37 -08:00 committed by Anas Nashif
parent 9e4772372f
commit 381df63fe8
1 changed files with 19 additions and 2 deletions
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21
drivers/dma/dma_qmsi.c
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@ -17,6 +17,13 @@
#include "qm_isr.h"
#include "clk.h"
#define CYCLE_NOP \
__asm__ __volatile__ ("nop"); \
__asm__ __volatile__ ("nop"); \
__asm__ __volatile__ ("nop"); \
__asm__ __volatile__ ("nop")
struct dma_qmsi_config_info {
qm_dma_t instance; /* Controller instance. */
};
@ -254,16 +261,26 @@ static int dma_qmsi_chan_config(struct device *dev, uint32_t channel,
static int dma_qmsi_transfer_start(struct device *dev, uint32_t channel)
{
int ret;
const struct dma_qmsi_config_info *info = dev->config->config_info;
return qm_dma_transfer_start(info->instance, channel);
ret = qm_dma_transfer_start(info->instance, channel);
CYCLE_NOP;
return ret;
}
static int dma_qmsi_start(struct device *dev, uint32_t channel)
{
int ret;
const struct dma_qmsi_config_info *info = dev->config->config_info;
return qm_dma_transfer_start(info->instance, channel);
ret = qm_dma_transfer_start(info->instance, channel);
CYCLE_NOP;
return ret;
}
static int dma_qmsi_transfer_stop(struct device *dev, uint32_t channel)