Re: [PATCH v3] xen/rpi4: implement watchdog-based reset

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

> On 7 Oct 2020, at 23:38, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> 
> The preferred method to reboot RPi4 is PSCI. If it is not available,
> touching the watchdog is required to be able to reboot the board.
> 
> The implementation is based on
> drivers/watchdog/bcm2835_wdt.c:__bcm2835_restart in Linux v5.9-rc7.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
> Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>

Maybe a printk if reset was not successful ?

Cheers
Bertrand

> CC: roman@xxxxxxxxxx
> ---
> Changes in v3:
> - fix typo in commit message
> - dprintk -> printk
> ---
> xen/arch/arm/platforms/brcm-raspberry-pi.c | 61 ++++++++++++++++++++++
> 1 file changed, 61 insertions(+)
> 
> diff --git a/xen/arch/arm/platforms/brcm-raspberry-pi.c 
> b/xen/arch/arm/platforms/brcm-raspberry-pi.c
> index f5ae58a7d5..811b40b1a6 100644
> --- a/xen/arch/arm/platforms/brcm-raspberry-pi.c
> +++ b/xen/arch/arm/platforms/brcm-raspberry-pi.c
> @@ -17,6 +17,10 @@
>  * GNU General Public License for more details.
>  */
> 
> +#include <xen/delay.h>
> +#include <xen/mm.h>
> +#include <xen/vmap.h>
> +#include <asm/io.h>
> #include <asm/platform.h>
> 
> static const char *const rpi4_dt_compat[] __initconst =
> @@ -37,12 +41,69 @@ static const struct dt_device_match rpi4_blacklist_dev[] 
> __initconst =
>      * The aux peripheral also shares a page with the aux UART.
>      */
>     DT_MATCH_COMPATIBLE("brcm,bcm2835-aux"),
> +    /* Special device used for rebooting */
> +    DT_MATCH_COMPATIBLE("brcm,bcm2835-pm"),
>     { /* sentinel */ },
> };
> 
> +
> +#define PM_PASSWORD                 0x5a000000
> +#define PM_RSTC                     0x1c
> +#define PM_WDOG                     0x24
> +#define PM_RSTC_WRCFG_FULL_RESET    0x00000020
> +#define PM_RSTC_WRCFG_CLR           0xffffffcf
> +
> +static void __iomem *rpi4_map_watchdog(void)
> +{
> +    void __iomem *base;
> +    struct dt_device_node *node;
> +    paddr_t start, len;
> +    int ret;
> +
> +    node = dt_find_compatible_node(NULL, NULL, "brcm,bcm2835-pm");
> +    if ( !node )
> +        return NULL;
> +
> +    ret = dt_device_get_address(node, 0, &start, &len);
> +    if ( ret )
> +    {
> +        printk("Cannot read watchdog register address\n");
> +        return NULL;
> +    }
> +
> +    base = ioremap_nocache(start & PAGE_MASK, PAGE_SIZE);
> +    if ( !base )
> +    {
> +        printk("Unable to map watchdog register!\n");
> +        return NULL;
> +    }
> +
> +    return base;
> +}
> +
> +static void rpi4_reset(void)
> +{
> +    uint32_t val;
> +    void __iomem *base = rpi4_map_watchdog();
> +
> +    if ( !base )
> +        return;
> +
> +    /* use a timeout of 10 ticks (~150us) */
> +    writel(10 | PM_PASSWORD, base + PM_WDOG);
> +    val = readl(base + PM_RSTC);
> +    val &= PM_RSTC_WRCFG_CLR;
> +    val |= PM_PASSWORD | PM_RSTC_WRCFG_FULL_RESET;
> +    writel(val, base + PM_RSTC);
> +
> +    /* No sleeping, possibly atomic. */
> +    mdelay(1);
> +}
> +
> PLATFORM_START(rpi4, "Raspberry Pi 4")
>     .compatible     = rpi4_dt_compat,
>     .blacklist_dev  = rpi4_blacklist_dev,
> +    .reset = rpi4_reset,
>     .dma_bitsize    = 30,
> PLATFORM_END
> 
> -- 
> 2.17.1
> 
>