Hi Ben,
2011/07/14 5:10, Ben Dooks wrote:
> On Fri, Jul 01, 2011 at 10:00:50AM +0900, Yoshihiro Shimoda wrote:
>> diff --git a/drivers/i2c/busses/i2c-riic.c b/drivers/i2c/busses/i2c-riic.c
>> index dcc183b..22dd779 100644
>> --- a/drivers/i2c/busses/i2c-riic.c
>> +++ b/drivers/i2c/busses/i2c-riic.c
>> @@ -30,6 +30,7 @@
>> #include <linux/timer.h>
>> #include <linux/delay.h>
>> #include <linux/slab.h>
>> +#include <linux/dmaengine.h>
>>
>> #define RIIC_ICCR1 0x00
>> #define RIIC_ICCR2 0x01
>> @@ -164,6 +165,14 @@ struct riic_data {
>> void __iomem *reg;
>> struct i2c_adapter adap;
>> struct i2c_msg *msg;
>> + int index;
>> + unsigned char icsr2;
>> +
>> + /* for DMAENGINE */
>> + struct dma_chan *chan_tx;
>> + struct dma_chan *chan_rx;
>> + int dma_callbacked;
>> + wait_queue_head_t wait;
>> };
>
> What happens if the driver is compiled into a kernel
> without dma engine support?
I could compile the code without enabling "CONFIG_DMA_ENGINE".
This is because The "struct dma_chan" is always defined in
the "include/linux/dmaengine.h", I think.
>> +static int riic_master_transmit_dma(struct riic_data *pd)
>> +{
>> + struct scatterlist sg;
>> + unsigned char *buf = pd->msg->buf;
>> + struct dma_async_tx_descriptor *desc;
>> + int ret;
>> +
>> + sg_init_table(&sg, 1);
>> + sg_set_buf(&sg, buf, pd->msg->len);
>> + sg_dma_len(&sg) = pd->msg->len;
>> + dma_map_sg(pd->chan_tx->device->dev, &sg, 1, DMA_TO_DEVICE);
>> +
>> + desc = pd->chan_tx->device->device_prep_slave_sg(pd->chan_tx,
>> + &sg, 1, DMA_TO_DEVICE,
>> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
>
> surely there's a better way of calling this?
Umm, I checked other drivers in the "drivers/", but I didn't find
a better way. Also other drivers was similar code...
>> + dmaengine_submit(desc);
>> + dma_async_issue_pending(pd->chan_rx);
>> +
>> + ret = wait_event_timeout(pd->wait, pd->dma_callbacked, HZ);
>> + if (!pd->dma_callbacked && !ret) {
>
> hmm, if you did not time out, then you should be able to
> infer the pd->dma_callbacked?
If this did not time out, the pd->dma_callbacked is always set.
So, I will fix the code to "if (!ret && !pd->dma_callbacked) {".
>> +static void riic_request_dma(struct riic_data *pd,
>> + struct riic_platform_data *riic_data)
>> +{
>> + dma_cap_mask_t mask;
>> +
>> + if (riic_data->dma_tx.slave_id) {
>> + dma_cap_zero(mask);
>> + dma_cap_set(DMA_SLAVE, mask);
>> + pd->chan_tx = dma_request_channel(mask, riic_filter,
>> + &riic_data->dma_tx);
>> + }
>> + if (riic_data->dma_rx.slave_id) {
>> + dma_cap_zero(mask);
>> + dma_cap_set(DMA_SLAVE, mask);
>> + pd->chan_rx = dma_request_channel(mask, riic_filter,
>> + &riic_data->dma_rx);
>> + }
>> +}
>
> should there be a warning if the slave_id is valid and
> the dma channel cannot be requested?
I will add a warning message.
However, even if the driver doesn't use dma, it can use PIO mode.
Best regards,
Yoshihiro Shimoda
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