On 08/09/2017 06:02 AM, David Gibson wrote:
> On Tue, Aug 08, 2017 at 10:56:18AM +0200, Cédric Le Goater wrote:
>> '/ibm,plat-res-int-priorities' contains a list of priorities that the
>> hypervisor has reserved for its own use. Scan these ranges to choose
>> the lowest unused priority for the xive spapr backend.
>>
>> Signed-off-by: Cédric Le Goater <c...@kaod.org>
>> ---
>> arch/powerpc/sysdev/xive/spapr.c | 62
>> +++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 61 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/powerpc/sysdev/xive/spapr.c
>> b/arch/powerpc/sysdev/xive/spapr.c
>> index 7fc40047c23d..220331986bd8 100644
>> --- a/arch/powerpc/sysdev/xive/spapr.c
>> +++ b/arch/powerpc/sysdev/xive/spapr.c
>> @@ -532,13 +532,70 @@ static const struct xive_ops xive_spapr_ops = {
>> .name = "spapr",
>> };
>>
>> +/*
>> + * get max priority from "/ibm,plat-res-int-priorities"
>> + */
>> +static bool xive_get_max_prio(u8 *max_prio)
>> +{
>> + struct device_node *rootdn;
>> + const __be32 *reg;
>> + u32 len;
>> + int prio, found;
>> +
>> + rootdn = of_find_node_by_path("/");
>> + if (!rootdn) {
>> + pr_err("not root node found !\n");
>> + return false;
>> + }
>> +
>> + reg = of_get_property(rootdn, "ibm,plat-res-int-priorities", &len);
>> + if (!reg) {
>> + pr_err("Failed to read 'ibm,plat-res-int-priorities'
>> property\n");
>> + return false;
>> + }
>> +
>> + if (len % (2 * sizeof(u32)) != 0) {
>> + pr_err("invalid 'ibm,plat-res-int-priorities' property\n");
>> + return false;
>> + }
>> +
>> + /* HW supports priorities in the range [0-7] and 0xFF is a
>> + * wildcard priority used to mask. We scan the ranges reserved
>> + * by the hypervisor to find the lowest priority we can use.
>> + */
>> + found = 0xFF;
>> + for (prio = 0; prio < 8; prio++) {
>> + int reserved = 0;
>> + int i;
>> +
>> + for (i = 0; i < len / (2 * sizeof(u32)); i++) {
>> + int base = be32_to_cpu(reg[2 * i]);
>> + int range = be32_to_cpu(reg[2 * i + 1]);
>> +
>> + if (prio >= base && prio < base + range)
>> + reserved++;
>> + }
>> +
>> + if (!reserved)
>> + found = prio;
>
> So you continue the loop here, rather than using break. Which means
> found will be the highest valued priority that's not reserved. Is
> that what you intended? The commit message says you find the lowest
> unused, but do lower numbers mean higher priorities or the other way around?
yes. I should probably add a statement on how the priorities are
ordered : the most privileged is the lowest value.
Thanks,
C.
>> + }
>> +
>> + if (found == 0xFF) {
>> + pr_err("no valid priority found in
>> 'ibm,plat-res-int-priorities'\n");
>> + return false;
>> + }
>> +
>> + *max_prio = found;
>> + return true;
>> +}
>> +
>> bool xive_spapr_init(void)
>> {
>> struct device_node *np;
>> struct resource r;
>> void __iomem *tima;
>> struct property *prop;
>> - u8 max_prio = 7;
>> + u8 max_prio;
>> u32 val;
>> u32 len;
>> const __be32 *reg;
>> @@ -566,6 +623,9 @@ bool xive_spapr_init(void)
>> return false;
>> }
>>
>> + if (!xive_get_max_prio(&max_prio))
>> + return false;
>> +
>> /* Feed the IRQ number allocator with the ranges given in the DT */
>> reg = of_get_property(np, "ibm,xive-lisn-ranges", &len);
>> if (!reg) {
>
