[U-Boot] [PATCH] ATA: Squash warnings in mxc_ata.

Stefano Babic
2011-09-23T09:27:36Z

On 09/23/2011 11:12 AM, Marek Vasut wrote:

Hi Marek,

> mxc_ata.c: In function ?set_ata_bus_timing?:
> mxc_ata.c:118: warning: dereferencing type-punned pointer will break
> strict-aliasing rules
> mxc_ata.c:125: warning: dereferencing type-punned pointer will break
> strict-aliasing rules
> mxc_ata.c:129: warning: dereferencing type-punned pointer will break
> strict-aliasing rules
>
> Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
> Cc: Stefano Babic <sbabic@denx.de>
> ---
> drivers/block/mxc_ata.c | 10 +++++++---
> 1 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/block/mxc_ata.c b/drivers/block/mxc_ata.c
> index f22f4f4..d94ec9c 100644
> --- a/drivers/block/mxc_ata.c
> +++ b/drivers/block/mxc_ata.c
> @@ -98,6 +98,7 @@ static void set_ata_bus_timing(unsigned char mode)
> {
> uint32_t val;
> uint32_t T = 1000000000 / mxc_get_clock(MXC_IPG_CLK);
> + uint32_t reg;
>
> struct mxc_ata_config_regs *ata_regs;
> ata_regs = (struct mxc_ata_config_regs *)CONFIG_SYS_ATA_BASE_ADDR;
> @@ -106,22 +107,25 @@ static void set_ata_bus_timing(unsigned char mode)
> return;
>
> /* Write TIME_OFF/ON/1/2W */
> + reg = (uint32_t)&ata_regs->time_off;

You drop the warnings using casting, but is it correct ? time_off is
defined as u8 (correctly, because this is the size of the register). If
you write 32bit, you risk to overwrite the time_on, time_1 and time_2w
registers.
Why do not use writeb ?

> val = (3 << REG2OFF(&ata_regs->time_off)) |
> (3 << REG2OFF(&ata_regs->time_on)) |
> (((pio_t1[mode] + T) / T) << REG2OFF(&ata_regs->time_1)) |
> (((pio_t2_8[mode] + T) / T) << REG2OFF(&ata_regs->time_2w));
> - writel(val, &ata_regs->time_off);
> + writel(val, reg);

Understood. You *want* to write all registers in one shot. However this
is hackish. Or you write each register separetely, or you use a union to
access the register block with a 32 bit access. Everybody reading
"writel(val, &ata_regs->time_off)" expects that time_off is 32bit wide.