lkml.org 
[lkml]   [2020]   [Sep]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v2 08/21] spi: dw: Refactor data IO procedure
Date
The Tx and Rx data write/read procedure can be significantly simplified by
using Tx/Rx transfer lengths instead of the end pointers. By having the
Tx/Rx data leftover lengths (in the number of transfer words) we can get
rid of all subtraction and division operations utilized here and there in
the tx_max(), rx_max(), dw_writer() and dw_reader() methods. Such
modification will not only give us the more optimized IO procedures, but
will make the data IO methods much more readable than before.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
---
drivers/spi/spi-dw-core.c | 37 +++++++++++++++++--------------------
drivers/spi/spi-dw.h | 5 ++---
2 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/drivers/spi/spi-dw-core.c b/drivers/spi/spi-dw-core.c
index 92c26b02269b..4baf72b121c2 100644
--- a/drivers/spi/spi-dw-core.c
+++ b/drivers/spi/spi-dw-core.c
@@ -108,9 +108,8 @@ EXPORT_SYMBOL_GPL(dw_spi_set_cs);
/* Return the max entries we can fill into tx fifo */
static inline u32 tx_max(struct dw_spi *dws)
{
- u32 tx_left, tx_room, rxtx_gap;
+ u32 tx_room, rxtx_gap;

- tx_left = (dws->tx_end - dws->tx) / dws->n_bytes;
tx_room = dws->fifo_len - dw_readl(dws, DW_SPI_TXFLR);

/*
@@ -121,18 +120,15 @@ static inline u32 tx_max(struct dw_spi *dws)
* shift registers. So a control from sw point of
* view is taken.
*/
- rxtx_gap = ((dws->rx_end - dws->rx) - (dws->tx_end - dws->tx))
- / dws->n_bytes;
+ rxtx_gap = dws->fifo_len - (dws->rx_len - dws->tx_len);

- return min3(tx_left, tx_room, (u32) (dws->fifo_len - rxtx_gap));
+ return min3((u32)dws->tx_len, tx_room, rxtx_gap);
}

/* Return the max entries we should read out of rx fifo */
static inline u32 rx_max(struct dw_spi *dws)
{
- u32 rx_left = (dws->rx_end - dws->rx) / dws->n_bytes;
-
- return min_t(u32, rx_left, dw_readl(dws, DW_SPI_RXFLR));
+ return min_t(u32, dws->rx_len, dw_readl(dws, DW_SPI_RXFLR));
}

static void dw_writer(struct dw_spi *dws)
@@ -141,15 +137,16 @@ static void dw_writer(struct dw_spi *dws)
u16 txw = 0;

while (max--) {
- /* Set the tx word if the transfer's original "tx" is not null */
- if (dws->tx_end - dws->len) {
+ if (dws->tx) {
if (dws->n_bytes == 1)
txw = *(u8 *)(dws->tx);
else
txw = *(u16 *)(dws->tx);
+
+ dws->tx += dws->n_bytes;
}
dw_write_io_reg(dws, DW_SPI_DR, txw);
- dws->tx += dws->n_bytes;
+ --dws->tx_len;
}
}

@@ -160,14 +157,15 @@ static void dw_reader(struct dw_spi *dws)

while (max--) {
rxw = dw_read_io_reg(dws, DW_SPI_DR);
- /* Care rx only if the transfer's original "rx" is not null */
- if (dws->rx_end - dws->len) {
+ if (dws->rx) {
if (dws->n_bytes == 1)
*(u8 *)(dws->rx) = rxw;
else
*(u16 *)(dws->rx) = rxw;
+
+ dws->rx += dws->n_bytes;
}
- dws->rx += dws->n_bytes;
+ --dws->rx_len;
}
}

@@ -192,7 +190,7 @@ static irqreturn_t interrupt_transfer(struct dw_spi *dws)
}

dw_reader(dws);
- if (dws->rx_end == dws->rx) {
+ if (!dws->rx_len) {
spi_mask_intr(dws, 0xff);
spi_finalize_current_transfer(dws->master);
return IRQ_HANDLED;
@@ -320,12 +318,11 @@ static int dw_spi_transfer_one(struct spi_controller *master,
dws->dma_mapped = 0;
dws->n_bytes = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
dws->tx = (void *)transfer->tx_buf;
- dws->tx_end = dws->tx + transfer->len;
+ dws->tx_len = transfer->len / dws->n_bytes;
dws->rx = transfer->rx_buf;
- dws->rx_end = dws->rx + transfer->len;
- dws->len = transfer->len;
+ dws->rx_len = dws->tx_len;

- /* Ensure dw->rx and dw->rx_end are visible */
+ /* Ensure the data above is visible for all CPUs */
smp_mb();

spi_enable_chip(dws, 0);
@@ -352,7 +349,7 @@ static int dw_spi_transfer_one(struct spi_controller *master,
return ret;
}
} else {
- txlevel = min_t(u16, dws->fifo_len / 2, dws->len / dws->n_bytes);
+ txlevel = min_t(u16, dws->fifo_len / 2, dws->tx_len);
dw_writel(dws, DW_SPI_TXFTLR, txlevel);

/* Set the interrupt mask */
diff --git a/drivers/spi/spi-dw.h b/drivers/spi/spi-dw.h
index 2a2346438564..cfc9f63acde4 100644
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -147,11 +147,10 @@ struct dw_spi {
void (*set_cs)(struct spi_device *spi, bool enable);

/* Current message transfer state info */
- size_t len;
void *tx;
- void *tx_end;
+ unsigned int tx_len;
void *rx;
- void *rx_end;
+ unsigned int rx_len;
int dma_mapped;
u8 n_bytes; /* current is a 1/2 bytes op */
irqreturn_t (*transfer_handler)(struct dw_spi *dws);
--
2.27.0
\
 
 \ /
  Last update: 2020-09-30 20:56    [W:0.178 / U:15.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site