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spi-topcliff-pch: Fix overrun issue 

We found that adding load, Rx data sometimes drops.(with DMA transfer mode)
The cause is that before starting Rx-DMA processing, Tx-DMA processing starts.
This causes FIFO overrun occurs.

This patch fixes the issue by modifying FIFO tx-threshold and DMA descriptor
size like below.

                      Current                   this patch
Rx-descriptor   4Byte+12Byte*341    -->    12Byte*340-4Byte-12Byte
Rx-threshold                   (Not modified)
Tx-descriptor   4Byte+12Byte*341    -->    16Byte-12Byte*340
Rx-threshold    12Byte              -->    2Byte

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
hifive-unleashed-5.1
Tomoya MORINAGA 2011-09-06 17:16:38 +09:00 committed by Grant Likely
parent 25e803f9c3
commit f3e03e2eb0
1 changed files with 23 additions and 5 deletions
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28
drivers/spi/spi-topcliff-pch.c
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@ -50,6 +50,8 @@
#define PCH_RX_THOLD 7
#define PCH_RX_THOLD_MAX 15
#define PCH_TX_THOLD 2
#define PCH_MAX_BAUDRATE 5000000
#define PCH_MAX_FIFO_DEPTH 16
@ -1040,8 +1042,7 @@ static void pch_spi_handle_dma(struct pch_spi_data *data, int *bpw)
/* set receive fifo threshold and transmit fifo threshold */
pch_spi_setclr_reg(data->master, PCH_SPCR,
((size - 1) << SPCR_RFIC_FIELD) |
((PCH_MAX_FIFO_DEPTH - PCH_DMA_TRANS_SIZE) <<
SPCR_TFIC_FIELD),
(PCH_TX_THOLD << SPCR_TFIC_FIELD),
MASK_RFIC_SPCR_BITS | MASK_TFIC_SPCR_BITS);
spin_unlock_irqrestore(&data->lock, flags);
@ -1052,13 +1053,20 @@ static void pch_spi_handle_dma(struct pch_spi_data *data, int *bpw)
/* offset, length setting */
sg = dma->sg_rx_p;
for (i = 0; i < num; i++, sg++) {
if (i == 0) {
sg->offset = 0;
if (i == (num - 2)) {
sg->offset = size * i;
sg->offset = sg->offset * (*bpw / 8);
sg_set_page(sg, virt_to_page(dma->rx_buf_virt), rem,
sg->offset);
sg_dma_len(sg) = rem;
} else if (i == (num - 1)) {
sg->offset = size * (i - 1) + rem;
sg->offset = sg->offset * (*bpw / 8);
sg_set_page(sg, virt_to_page(dma->rx_buf_virt), size,
sg->offset);
sg_dma_len(sg) = size;
} else {
sg->offset = rem + size * (i - 1);
sg->offset = size * i;
sg->offset = sg->offset * (*bpw / 8);
sg_set_page(sg, virt_to_page(dma->rx_buf_virt), size,
sg->offset);
@ -1082,6 +1090,16 @@ static void pch_spi_handle_dma(struct pch_spi_data *data, int *bpw)
dma->desc_rx = desc_rx;
/* TX */
if (data->bpw_len > PCH_DMA_TRANS_SIZE) {
num = data->bpw_len / PCH_DMA_TRANS_SIZE;
size = PCH_DMA_TRANS_SIZE;
rem = 16;
} else {
num = 1;
size = data->bpw_len;
rem = data->bpw_len;
}
dma->sg_tx_p = kzalloc(sizeof(struct scatterlist)*num, GFP_ATOMIC);
sg_init_table(dma->sg_tx_p, num); /* Initialize SG table */
/* offset, length setting */