From 5eca2914f3cf787cced92e818bff5f1ac4f0a8b2 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Mon, 27 Jun 2016 11:19:13 +0200 Subject: [PATCH] dsa: b53: avoid 'maybe-uninitialized' warning In some configurations, gcc produces a warning for correct code in this driver: drivers/net/dsa/b53/b53_mmap.c: In function 'b53_mmap_read64': drivers/net/dsa/b53/b53_mmap.c:107:10: error: 'hi' may be used uninitialized in this function [-Werror=maybe-uninitialized] *val = ((u64)hi << 32) | lo; ^~~~~~~ drivers/net/dsa/b53/b53_mmap.c: In function 'b53_mmap_read48': drivers/net/dsa/b53/b53_mmap.c:91:11: error: 'hi' may be used uninitialized in this function [-Werror=maybe-uninitialized] *val = ((u64)hi << 32) | lo; ^~~~~~~ drivers/net/dsa/b53/b53_mmap.c:83:11: error: 'hi' may be used uninitialized in this function [-Werror=maybe-uninitialized] *val = ((u64)hi << 16) | lo; I have seen the warning before and at the time thought I had fixed it with 55e7f6abe131 ("dsa: b53: fix big-endian register access"), however it now came back in a different randconfig build that happens to have different inlining decisions in the compiler. The mistake that gcc makes here is that it thinks the second call to readl() might fail because the address 'reg + 4' is not a multiple of four despite having knowing that 'reg' itself is a multiple of four. By open-coding the two reads without the redundant alignment check, we can avoid the warning and produce slightly better object code, but get slightly longer source code instead. Signed-off-by: Arnd Bergmann Signed-off-by: David S. Miller --- drivers/net/dsa/b53/b53_mmap.c | 30 ++++++++++++++++++++++++------ 1 file changed, 24 insertions(+), 6 deletions(-) diff --git a/drivers/net/dsa/b53/b53_mmap.c b/drivers/net/dsa/b53/b53_mmap.c index b70daf9174d4..21f1068b0804 100644 --- a/drivers/net/dsa/b53/b53_mmap.c +++ b/drivers/net/dsa/b53/b53_mmap.c @@ -70,6 +70,8 @@ static int b53_mmap_read32(struct b53_device *dev, u8 page, u8 reg, u32 *val) static int b53_mmap_read48(struct b53_device *dev, u8 page, u8 reg, u64 *val) { + u8 __iomem *regs = dev->priv; + if (WARN_ON(reg % 2)) return -EINVAL; @@ -77,16 +79,26 @@ static int b53_mmap_read48(struct b53_device *dev, u8 page, u8 reg, u64 *val) u16 lo; u32 hi; - b53_mmap_read16(dev, page, reg, &lo); - b53_mmap_read32(dev, page, reg + 2, &hi); + if (dev->pdata && dev->pdata->big_endian) { + lo = ioread16be(regs + (page << 8) + reg); + hi = ioread32be(regs + (page << 8) + reg + 2); + } else { + lo = readw(regs + (page << 8) + reg); + hi = readl(regs + (page << 8) + reg + 2); + } *val = ((u64)hi << 16) | lo; } else { u32 lo; u16 hi; - b53_mmap_read32(dev, page, reg, &lo); - b53_mmap_read16(dev, page, reg + 4, &hi); + if (dev->pdata && dev->pdata->big_endian) { + lo = ioread32be(regs + (page << 8) + reg); + hi = ioread16be(regs + (page << 8) + reg + 4); + } else { + lo = readl(regs + (page << 8) + reg); + hi = readw(regs + (page << 8) + reg + 4); + } *val = ((u64)hi << 32) | lo; } @@ -96,13 +108,19 @@ static int b53_mmap_read48(struct b53_device *dev, u8 page, u8 reg, u64 *val) static int b53_mmap_read64(struct b53_device *dev, u8 page, u8 reg, u64 *val) { + u8 __iomem *regs = dev->priv; u32 hi, lo; if (WARN_ON(reg % 4)) return -EINVAL; - b53_mmap_read32(dev, page, reg, &lo); - b53_mmap_read32(dev, page, reg + 4, &hi); + if (dev->pdata && dev->pdata->big_endian) { + lo = ioread32be(regs + (page << 8) + reg); + hi = ioread32be(regs + (page << 8) + reg + 4); + } else { + lo = readl(regs + (page << 8) + reg); + hi = readl(regs + (page << 8) + reg + 4); + } *val = ((u64)hi << 32) | lo; -- 2.20.1