Re: [PATCH v5 2/4] irqchip/gic-v3-its: add ability to save/restore ITS state

Marc Zyngier
2018-02-07T09:18:20Z

On 07/02/18 01:41, Derek Basehore wrote:
> Some platforms power off GIC logic in suspend, so we need to
> save/restore state. The distributor and redistributor registers need
> to be handled in platform code due to access permissions on those
> registers, but the ITS registers can be restored in the kernel.
>
> Signed-off-by: Derek Basehore <dbasehore@chromium.org>
> ---
> drivers/irqchip/irq-gic-v3-its.c | 99 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 99 insertions(+)
>
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index 06f025fd5726..5e63635e2a7b 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -33,6 +33,7 @@
> #include <linux/of_platform.h>
> #include <linux/percpu.h>
> #include <linux/slab.h>
> +#include <linux/syscore_ops.h>
>
> #include <linux/irqchip.h>
> #include <linux/irqchip/arm-gic-v3.h>
> @@ -46,6 +47,7 @@
> #define ITS_FLAGS_CMDQ_NEEDS_FLUSHING (1ULL << 0)
> #define ITS_FLAGS_WORKAROUND_CAVIUM_22375 (1ULL << 1)
> #define ITS_FLAGS_WORKAROUND_CAVIUM_23144 (1ULL << 2)
> +#define ITS_FLAGS_SAVE_SUSPEND_STATE (1ULL << 3)
>
> #define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING (1 << 0)
>
> @@ -101,6 +103,8 @@ struct its_node {
> struct its_collection *collections;
> struct fwnode_handle *fwnode_handle;
> u64 (*get_msi_base)(struct its_device *its_dev);
> + u64 cbaser_save;
> + u32 ctlr_save;
> struct list_head its_device_list;
> u64 flags;
> unsigned long list_nr;
> @@ -3042,6 +3046,96 @@ static void its_enable_quirks(struct its_node *its)
> gic_enable_quirks(iidr, its_quirks, its);
> }
>
> +static int its_save_disable(void)
> +{
> + struct its_node *its;
> + int err = 0;
> +
> + spin_lock(&its_lock);
> + list_for_each_entry(its, &its_nodes, entry) {
> + void __iomem *base;
> +
> + if (!(its->flags & ITS_FLAGS_SAVE_SUSPEND_STATE))
> + continue;
> +
> + base = its->base;
> + its->ctlr_save = readl_relaxed(base + GITS_CTLR);
> + err = its_force_quiescent(base);
> + if (err) {
> + pr_err("ITS failed to quiesce\n");
> + writel_relaxed(its->ctlr_save, base + GITS_CTLR);
> + goto err;
> + }
> +
> + its->cbaser_save = gits_read_cbaser(base + GITS_CBASER);
> + }
> +
> +err:
> + if (err) {
> + list_for_each_entry_continue_reverse(its, &its_nodes, entry) {
> + void __iomem *base;
> +
> + if (!(its->flags & ITS_FLAGS_SAVE_SUSPEND_STATE))
> + continue;
> +
> + base = its->base;
> + writel_relaxed(its->ctlr_save, base + GITS_CTLR);
> + }
> + }
> + spin_unlock(&its_lock);
> +
> + return err;
> +}
> +
> +static void its_restore_enable(void)
> +{
> + struct its_node *its;
> +
> + spin_lock(&its_lock);
> + list_for_each_entry(its, &its_nodes, entry) {
> + void __iomem *base;
> + int i;
> +
> + if (!(its->flags & ITS_FLAGS_SAVE_SUSPEND_STATE))
> + continue;
> +
> + base = its->base;
> +
> + /*
> + * Make sure that the ITS is disabled. There's not much we can
> + * do if this fails.
> + */
> + if (its_force_quiescent(base))
> + pr_err("ITS failed to quiesce on resume\n");

One thing we can do though is to abort the resume of this ITS, because
"When GITS_CTLR.Enabled == 1 or GITS_CTLR.Quiescent == 0, writing this
register is UNPREDICTABLE." (where "this register" is any of the
GITS_BASER<n>).

Printing the physical base address of the failing ITS can also help
people to debug their HW (my toy platform has 8 of them...).

> +
> + gits_write_cbaser(its->cbaser_save, base + GITS_CBASER);
> +
> + /*
> + * Writing CBASER resets CREADR to 0, so make CWRITER and
> + * cmd_write line up with it.
> + */
> + its->cmd_write = its->cmd_base;
> + gits_write_cwriter(0, base + GITS_CWRITER);
> +
> + /* Restore GITS_BASER from the value cache. */
> + for (i = 0; i < GITS_BASER_NR_REGS; i++) {
> + struct its_baser *baser = &its->tables[i];
> +
> + if (!(baser->val & GITS_BASER_VALID))
> + continue;
> +
> + its_write_baser(its, baser, baser->val);
> + }
> + writel_relaxed(its->ctlr_save, base + GITS_CTLR);
> + }
> + spin_unlock(&its_lock);
> +}
> +
> +static struct syscore_ops its_syscore_ops = {
> + .suspend = its_save_disable,
> + .resume = its_restore_enable,
> +};
> +
> static int its_init_domain(struct fwnode_handle *handle, struct its_node *its)
> {
> struct irq_domain *inner_domain;
> @@ -3261,6 +3355,9 @@ static int __init its_probe_one(struct resource *res,
> ctlr |= GITS_CTLR_ImDe;
> writel_relaxed(ctlr, its->base + GITS_CTLR);
>
> + if (fwnode_property_present(handle, "reset-on-suspend"))
> + its->flags |= ITS_FLAGS_SAVE_SUSPEND_STATE;
> +
> err = its_init_domain(handle, its);
> if (err)
> goto out_free_tables;
> @@ -3515,5 +3612,7 @@ int __init its_init(struct fwnode_handle *handle, struct rdists *rdists,
> }
> }
>
> + register_syscore_ops(&its_syscore_ops);
> +
> return 0;
> }
>

Otherwise starting to look OK.

Thanks,

M.
--
Jazz is not dead. It just smells funny...