Re: [PATCH 2/2] watchdog: imx2_wdt: Add big-endian support

[Guenter Roeck <linux@roeck-us.net>]

On 03/25/2014 02:35 AM, Xiubo Li wrote:
> Signed-off-by: Xiubo Li <Li.Xiubo@freescale.com>
> ---

There is no explanation for this patch in the headline.

Ultimately there are four cases
	CPU	HW
	little	little
	little	big
	big	little
	big	big
Current code handles big/big as well as little/little, and you are adding
little/big to the list of supported combinations. Questions are
1) which combinations are possible ?
2) is big/little a combination which needs to be handled as well ?
	
The "big-endians" property is new and will have to be approved by the
DT maintainers. If in fact needed, I would suggest to use "big-endian"
as this seems to be more common.

Guenter


>   drivers/watchdog/imx2_wdt.c | 40 +++++++++++++++++++++++++++++++---------
>   1 file changed, 31 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
> index 1795922..c410981 100644
> --- a/drivers/watchdog/imx2_wdt.c
> +++ b/drivers/watchdog/imx2_wdt.c
> @@ -30,6 +30,7 @@
>   #include <linux/miscdevice.h>
>   #include <linux/module.h>
>   #include <linux/moduleparam.h>
> +#include <linux/of.h>
>   #include <linux/platform_device.h>
>   #include <linux/timer.h>
>   #include <linux/uaccess.h>
> @@ -64,9 +65,26 @@ static struct {
>   	void __iomem *base;
>   	unsigned timeout;
>   	unsigned long status;
> +	bool big_endian;
>   	struct timer_list timer;	/* Pings the watchdog when closed */
>   } imx2_wdt;
>
> +static inline u16 imx2_wdt_readw(void __iomem *addr)
> +{
> +	if (imx2_wdt.big_endian)
> +		return ioread16be(addr);
> +	else
> +		return ioread16(addr);
> +}
> +
> +static inline void imx2_wdt_writew(u16 val, void __iomem *addr)
> +{
> +	if (imx2_wdt.big_endian)
> +		iowrite16be(val, addr);
> +	else
> +		iowrite16(val, addr);
> +}
> +
>   static struct miscdevice imx2_wdt_miscdev;
>
>   static bool nowayout = WATCHDOG_NOWAYOUT;
> @@ -87,7 +105,7 @@ static const struct watchdog_info imx2_wdt_info = {
>
>   static inline void imx2_wdt_setup(void)
>   {
> -	u16 val = __raw_readw(imx2_wdt.base + IMX2_WDT_WCR);
> +	u16 val = imx2_wdt_readw(imx2_wdt.base + IMX2_WDT_WCR);
>
>   	/* Suspend timer in low power mode, write once-only */
>   	val |= IMX2_WDT_WCR_WDZST;
> @@ -100,17 +118,17 @@ static inline void imx2_wdt_setup(void)
>   	/* Set the watchdog's Time-Out value */
>   	val |= WDOG_SEC_TO_COUNT(imx2_wdt.timeout);
>
> -	__raw_writew(val, imx2_wdt.base + IMX2_WDT_WCR);
> +	imx2_wdt_writew(val, imx2_wdt.base + IMX2_WDT_WCR);
>
>   	/* enable the watchdog */
>   	val |= IMX2_WDT_WCR_WDE;
> -	__raw_writew(val, imx2_wdt.base + IMX2_WDT_WCR);
> +	imx2_wdt_writew(val, imx2_wdt.base + IMX2_WDT_WCR);
>   }
>
>   static inline void imx2_wdt_ping(void)
>   {
> -	__raw_writew(IMX2_WDT_SEQ1, imx2_wdt.base + IMX2_WDT_WSR);
> -	__raw_writew(IMX2_WDT_SEQ2, imx2_wdt.base + IMX2_WDT_WSR);
> +	imx2_wdt_writew(IMX2_WDT_SEQ1, imx2_wdt.base + IMX2_WDT_WSR);
> +	imx2_wdt_writew(IMX2_WDT_SEQ2, imx2_wdt.base + IMX2_WDT_WSR);
>   }
>
>   static void imx2_wdt_timer_ping(unsigned long arg)
> @@ -143,12 +161,12 @@ static void imx2_wdt_stop(void)
>
>   static void imx2_wdt_set_timeout(int new_timeout)
>   {
> -	u16 val = __raw_readw(imx2_wdt.base + IMX2_WDT_WCR);
> +	u16 val = imx2_wdt_readw(imx2_wdt.base + IMX2_WDT_WCR);
>
>   	/* set the new timeout value in the WSR */
>   	val &= ~IMX2_WDT_WCR_WT;
>   	val |= WDOG_SEC_TO_COUNT(new_timeout);
> -	__raw_writew(val, imx2_wdt.base + IMX2_WDT_WCR);
> +	imx2_wdt_writew(val, imx2_wdt.base + IMX2_WDT_WCR);
>   }
>
>   static int imx2_wdt_open(struct inode *inode, struct file *file)
> @@ -192,7 +210,7 @@ static long imx2_wdt_ioctl(struct file *file, unsigned int cmd,
>   		return put_user(0, p);
>
>   	case WDIOC_GETBOOTSTATUS:
> -		val = __raw_readw(imx2_wdt.base + IMX2_WDT_WRSR);
> +		val = imx2_wdt_readw(imx2_wdt.base + IMX2_WDT_WRSR);
>   		new_value = val & IMX2_WDT_WRSR_TOUT ? WDIOF_CARDRESET : 0;
>   		return put_user(new_value, p);
>
> @@ -257,8 +275,12 @@ static struct miscdevice imx2_wdt_miscdev = {
>
>   static int __init imx2_wdt_probe(struct platform_device *pdev)
>   {
> -	int ret;
> +	struct device_node *np = pdev->dev.of_node;
>   	struct resource *res;
> +	int ret;
> +
> +	if (np)
> +		imx2_wdt.big_endian = of_property_read_bool(np, "big-endians");
>
>   	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>   	imx2_wdt.base = devm_ioremap_resource(&pdev->dev, res);
>