From 19d3e966d9ee535fc89e8fa26737cc133882ae1c Mon Sep 17 00:00:00 2001 From: Michael Brown Date: Thu, 23 Mar 2017 17:35:10 +0200 Subject: [PATCH] [pcnet32] Eliminate redundant register read The value of ( ( x & 0x0c00 ) | 0x0c00 ) is always 0x0c00 regardless of the value of x, and so the read_csr() is redundant. (There are no read side effects for this register, according to the datasheet.) This line of code originated in Linux kernel 2.3.19pre1 as a->write_csr(ioaddr, 80, a->read_csr(ioaddr, 80) | 0x0c00); and was modified in kernel 2.3.41pre4 to read a->write_csr(ioaddr, 80, (a->read_csr(ioaddr, 80) & 0x0C00) | 0x0c00); In the absence of commit messages, the intention of the code is unclear. However, the logic resulting in a fixed value of 0x0c00 has remained unaltered for over 17 years, and can probably be assumed to have the correct overall result. Signed-off-by: Michael Brown --- src/drivers/net/pcnet32.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/src/drivers/net/pcnet32.c b/src/drivers/net/pcnet32.c index 26633a24..2635aaca 100644 --- a/src/drivers/net/pcnet32.c +++ b/src/drivers/net/pcnet32.c @@ -414,8 +414,7 @@ pcnet32_chip_detect ( struct pcnet32_private *priv ) if (fset) { a->write_bcr ( ioaddr, 18, ( a->read_bcr ( ioaddr, 18 ) | 0x0860 ) ); - a->write_csr ( ioaddr, 80, - ( a->read_csr ( ioaddr, 80 ) & 0x0C00) | 0x0C00 ); + a->write_csr ( ioaddr, 80, 0x0c00 ); } priv->full_duplex = fdx;