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| author |   Baruch Siach <baruch@tkos.co.il> | 2008-12-18 19:39:14 -0800 |
|---|---|---|
| committer |   David S. Miller <davem@davemloft.net> | 2008-12-18 22:27:39 -0800 |
| commit | 5664dd5561850df580414783cf3c8e0aa834c62e (patch) | |
| tree | aac02f7e39a2adbac4920c131c1a49f6ddb571e2 /drivers/net/enc28j60.c | |
| parent | netdevice zd1201: Use after free (diff) | |
| download | linux-dev-5664dd5561850df580414783cf3c8e0aa834c62e.tar.xz linux-dev-5664dd5561850df580414783cf3c8e0aa834c62e.zip | |
enc28j60: reduce the number of spi transfers in enc28j60_set_bank()
A major source of overhead in the enc28j60 driver is the SPI transfers. Each
SPI transfer entails two kernel thread context switches. One major source of
SPI transfers is the enc28j60_set_bank() functions which runs before every
register access. This patch reduces the number of SPI transfers that
enc28j60_set_bank() performs in two ways:
1. removes unnecessary bank switch for the registers that are present in all
banks
2. when switching from banks 0 or 3 to banks 1 or 2 (i.e. only one bit
changes) enc28j60_set_bank() does only one SPI transfer instead of two
According to my tests these changes reduce the number of SPI transfers in
about 25%.
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/enc28j60.c')
| -rw-r--r-- | drivers/net/enc28j60.c | 30 |
1 files changed, 23 insertions, 7 deletions
diff --git a/drivers/net/enc28j60.c b/drivers/net/enc28j60.c index 535e14094971..b0ef46c51a9d 100644 --- a/drivers/net/enc28j60.c +++ b/drivers/net/enc28j60.c @@ -196,16 +196,32 @@ static void enc28j60_soft_reset(struct enc28j60_net *priv) */ static void enc28j60_set_bank(struct enc28j60_net *priv, u8 addr) { - if ((addr & BANK_MASK) != priv->bank) { - u8 b = (addr & BANK_MASK) >> 5; + u8 b = (addr & BANK_MASK) >> 5; - if (b != (ECON1_BSEL1 | ECON1_BSEL0)) + /* These registers (EIE, EIR, ESTAT, ECON2, ECON1) + * are present in all banks, no need to switch bank + */ + if (addr >= EIE && addr <= ECON1) + return; + + /* Clear or set each bank selection bit as needed */ + if ((b & ECON1_BSEL0) != (priv->bank & ECON1_BSEL0)) { + if (b & ECON1_BSEL0) + spi_write_op(priv, ENC28J60_BIT_FIELD_SET, ECON1, + ECON1_BSEL0); + else + spi_write_op(priv, ENC28J60_BIT_FIELD_CLR, ECON1, + ECON1_BSEL0); + } + if ((b & ECON1_BSEL1) != (priv->bank & ECON1_BSEL1)) { + if (b & ECON1_BSEL1) + spi_write_op(priv, ENC28J60_BIT_FIELD_SET, ECON1, + ECON1_BSEL1); + else spi_write_op(priv, ENC28J60_BIT_FIELD_CLR, ECON1, - ECON1_BSEL1 | ECON1_BSEL0); - if (b != 0) - spi_write_op(priv, ENC28J60_BIT_FIELD_SET, ECON1, b); - priv->bank = (addr & BANK_MASK); + ECON1_BSEL1); } + priv->bank = b; } /* |