From: Suzuki K Poulose <Suzuki.Poulose@arm.com>
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, robert.walker@arm.com,
mike.leach@arm.com
Subject: Re: [PATCH 08/13] coresight: Add support for CLAIM tag protocol
Date: Thu, 16 Aug 2018 16:47:30 +0100 [thread overview]
Message-ID: <4aff79b4-593e-a19b-5e3f-de2a6d5bacb7@arm.com> (raw)
In-Reply-To: <20180814232053.GA5131@xps15>
On 15/08/18 00:20, Mathieu Poirier wrote:
> On Mon, Aug 06, 2018 at 02:41:50PM +0100, Suzuki K Poulose wrote:
>> Add support for the CLAIM tag protocol for negotiating the
>> device ownership with other agents trying to use the coresight
>> component (internal vs. external). The Coresight architecture
>> specifies CLAIM tags (managed via CLAIMSET CLAIMCLR registers)
>> to negotiate the ownership of the device. PSCI recommends the
>> reservation of the bits in CLAIM tags for self-hosted and external
>> debug use. This patch implements the protocol for claiming
>> the devices before they are actually used.
>
> I think the first paragraph of the cover letter (minus the reference to the
> documentation since you've included it below) would be perfect instead of the
> above.
>
>>
>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>> ---
>> drivers/hwtracing/coresight/coresight-priv.h | 7 +++
>> drivers/hwtracing/coresight/coresight.c | 85 ++++++++++++++++++++++++++++
>> include/linux/coresight.h | 20 +++++++
>> 3 files changed, 112 insertions(+)
>> +void coresight_disclaim_device_unlocked(void __iomem *base)
>> +{
>> +
>> + if (coresight_is_claimed_self_hosted(base))
>> + coresight_clear_claim_tags(base);
>> + else
>> + /*
>> + * Either we or the external agent doesn't follow
>> + * the protocol.
>> + */
>> + WARN_ON_ONCE(1);
>
> When writing "... or the external agent doesn't follow the protocol", I deduce
> that an external agent would have trampled our claim tag. I think this needs
> to be said explicitly in the comment.
>
>> +static inline int coresight_claim_device_unlocked(void __iomem *base)
>> +{
>> + return 0;
>> +}
>> +
>> +static inline int coresight_claim_device(void __iomem *base)
>> +{
>> + return 0;
>> +}
>
> Returning 0 would give a caller the impression the operation has succeeded when
> in fact it didn't. I think we should return an error code here.
Agreed on all points, will respin.
Suzuki
next prev parent reply other threads:[~2018-08-16 15:47 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-06 13:41 [PATCH 00/13] coresight: Implement device claim protocol Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 01/13] coresight: tmc-etr: Refactor for handling errors Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 02/13] coresight: tmc-etr: Handle errors enabling CATU Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 03/13] coresight: tmc-etb/etf: Prepare to handle errors enabling Suzuki K Poulose
2018-08-15 19:22 ` Mathieu Poirier
2018-08-16 14:47 ` Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 04/13] coresight: etm4x: Add support for handling errors Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 05/13] coresight: etm3: " Suzuki K Poulose
2018-08-15 19:34 ` Mathieu Poirier
2018-08-16 15:45 ` Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 06/13] coresight: etb10: Handle errors enabling the device Suzuki K Poulose
2018-08-14 17:40 ` Mathieu Poirier
2018-08-15 19:38 ` Mathieu Poirier
2018-08-16 15:46 ` Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 07/13] coresight: dynamic-replicator: Handle multiple connections Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 08/13] coresight: Add support for CLAIM tag protocol Suzuki K Poulose
2018-08-14 23:20 ` Mathieu Poirier
2018-08-16 15:47 ` Suzuki K Poulose [this message]
2018-08-06 13:41 ` [PATCH 09/13] coresight: etmx: Claim devices before use Suzuki K Poulose
2018-08-14 23:43 ` Mathieu Poirier
2018-08-06 13:41 ` [PATCH 10/13] coresight: funnel: " Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 11/13] coresight: catu: Claim device " Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 12/13] coresight: dynamic-replicator: Claim device for use Suzuki K Poulose
2018-08-06 13:41 ` [PATCH 13/13] coreisght: tmc: Claim device before use Suzuki K Poulose
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