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linux/drivers/net/dsa/b53/b53_mmap.c
Arnd Bergmann 5eca2914f3 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 55e7f6abe1 ("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 <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
2016-06-29 05:07:12 -04:00

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/*
* B53 register access through memory mapped registers
*
* Copyright (C) 2012-2013 Jonas Gorski <jogo@openwrt.org>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <linux/kernel.h>
#include <linux/kconfig.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/platform_data/b53.h>
#include "b53_priv.h"
struct b53_mmap_priv {
void __iomem *regs;
};
static int b53_mmap_read8(struct b53_device *dev, u8 page, u8 reg, u8 *val)
{
u8 __iomem *regs = dev->priv;
*val = readb(regs + (page << 8) + reg);
return 0;
}
static int b53_mmap_read16(struct b53_device *dev, u8 page, u8 reg, u16 *val)
{
u8 __iomem *regs = dev->priv;
if (WARN_ON(reg % 2))
return -EINVAL;
if (dev->pdata && dev->pdata->big_endian)
*val = ioread16be(regs + (page << 8) + reg);
else
*val = readw(regs + (page << 8) + reg);
return 0;
}
static int b53_mmap_read32(struct b53_device *dev, u8 page, u8 reg, u32 *val)
{
u8 __iomem *regs = dev->priv;
if (WARN_ON(reg % 4))
return -EINVAL;
if (dev->pdata && dev->pdata->big_endian)
*val = ioread32be(regs + (page << 8) + reg);
else
*val = readl(regs + (page << 8) + reg);
return 0;
}
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;
if (reg % 4) {
u16 lo;
u32 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;
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;
}
return 0;
}
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;
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;
return 0;
}
static int b53_mmap_write8(struct b53_device *dev, u8 page, u8 reg, u8 value)
{
u8 __iomem *regs = dev->priv;
writeb(value, regs + (page << 8) + reg);
return 0;
}
static int b53_mmap_write16(struct b53_device *dev, u8 page, u8 reg,
u16 value)
{
u8 __iomem *regs = dev->priv;
if (WARN_ON(reg % 2))
return -EINVAL;
if (dev->pdata && dev->pdata->big_endian)
iowrite16be(value, regs + (page << 8) + reg);
else
writew(value, regs + (page << 8) + reg);
return 0;
}
static int b53_mmap_write32(struct b53_device *dev, u8 page, u8 reg,
u32 value)
{
u8 __iomem *regs = dev->priv;
if (WARN_ON(reg % 4))
return -EINVAL;
if (dev->pdata && dev->pdata->big_endian)
iowrite32be(value, regs + (page << 8) + reg);
else
writel(value, regs + (page << 8) + reg);
return 0;
}
static int b53_mmap_write48(struct b53_device *dev, u8 page, u8 reg,
u64 value)
{
if (WARN_ON(reg % 2))
return -EINVAL;
if (reg % 4) {
u32 hi = (u32)(value >> 16);
u16 lo = (u16)value;
b53_mmap_write16(dev, page, reg, lo);
b53_mmap_write32(dev, page, reg + 2, hi);
} else {
u16 hi = (u16)(value >> 32);
u32 lo = (u32)value;
b53_mmap_write32(dev, page, reg, lo);
b53_mmap_write16(dev, page, reg + 4, hi);
}
return 0;
}
static int b53_mmap_write64(struct b53_device *dev, u8 page, u8 reg,
u64 value)
{
u32 hi, lo;
hi = upper_32_bits(value);
lo = lower_32_bits(value);
if (WARN_ON(reg % 4))
return -EINVAL;
b53_mmap_write32(dev, page, reg, lo);
b53_mmap_write32(dev, page, reg + 4, hi);
return 0;
}
static struct b53_io_ops b53_mmap_ops = {
.read8 = b53_mmap_read8,
.read16 = b53_mmap_read16,
.read32 = b53_mmap_read32,
.read48 = b53_mmap_read48,
.read64 = b53_mmap_read64,
.write8 = b53_mmap_write8,
.write16 = b53_mmap_write16,
.write32 = b53_mmap_write32,
.write48 = b53_mmap_write48,
.write64 = b53_mmap_write64,
};
static int b53_mmap_probe(struct platform_device *pdev)
{
struct b53_platform_data *pdata = pdev->dev.platform_data;
struct b53_device *dev;
if (!pdata)
return -EINVAL;
dev = b53_switch_alloc(&pdev->dev, &b53_mmap_ops, pdata->regs);
if (!dev)
return -ENOMEM;
if (pdata)
dev->pdata = pdata;
platform_set_drvdata(pdev, dev);
return b53_switch_register(dev);
}
static int b53_mmap_remove(struct platform_device *pdev)
{
struct b53_device *dev = platform_get_drvdata(pdev);
if (dev)
b53_switch_remove(dev);
return 0;
}
static const struct of_device_id b53_mmap_of_table[] = {
{ .compatible = "brcm,bcm3384-switch" },
{ .compatible = "brcm,bcm6328-switch" },
{ .compatible = "brcm,bcm6368-switch" },
{ .compatible = "brcm,bcm63xx-switch" },
{ /* sentinel */ },
};
static struct platform_driver b53_mmap_driver = {
.probe = b53_mmap_probe,
.remove = b53_mmap_remove,
.driver = {
.name = "b53-switch",
.of_match_table = b53_mmap_of_table,
},
};
module_platform_driver(b53_mmap_driver);
MODULE_AUTHOR("Jonas Gorski <jogo@openwrt.org>");
MODULE_DESCRIPTION("B53 MMAP access driver");
MODULE_LICENSE("Dual BSD/GPL");
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