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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 8 Oct 2020, Bertrand Marquis wrote:
> > 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 ?

That not quite platform specific but we could add a printk to
xen/arch/arm/shutdown.c:machine_restart if we are still alive after
100ms.

I'll commit this patch as is and maybe send another one for
machine_restart.


> > 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
> > 
> > 
>