[PATCH 08/10] powerpc/xive: take into account '/ibm,plat-res-int-priorities'

[Cédric Le Goater]

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 <clg at 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) {
>