linux-kernel - Re: [PATCH v2 3/4] soc: qcom: smem: Add qcom_smem_bust_hwspin_lock_by

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Date: Tue, 28 May 2024 16:55:52 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Chris Lew <quic_clew@...cinc.com>
Cc: Baolin Wang <baolin.wang@...ux.alibaba.com>, 
	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>, 
	Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, 
	Jonathan Corbet <corbet@....net>, Mathieu Poirier <mathieu.poirier@...aro.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	Konrad Dybcio <konrad.dybcio@...aro.org>, linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 3/4] soc: qcom: smem: Add
 qcom_smem_bust_hwspin_lock_by_host()

On Fri, May 24, 2024 at 06:26:42PM GMT, Chris Lew wrote:
> Add qcom_smem_bust_hwspin_lock_by_host to enable remoteproc to bust the
> hwspin_lock owned by smem. In the event the remoteproc crashes
> unexpectedly, the remoteproc driver can invoke this API to try and bust
> the hwspin_lock and release the lock if still held by the remoteproc
> device.
> 
> Signed-off-by: Chris Lew <quic_clew@...cinc.com>
> ---
>  drivers/soc/qcom/smem.c       | 28 ++++++++++++++++++++++++++++
>  include/linux/soc/qcom/smem.h |  2 ++
>  2 files changed, 30 insertions(+)
> 
> diff --git a/drivers/soc/qcom/smem.c b/drivers/soc/qcom/smem.c
> index 7191fa0c087f..683599990387 100644
> --- a/drivers/soc/qcom/smem.c
> +++ b/drivers/soc/qcom/smem.c
> @@ -359,6 +359,34 @@ static struct qcom_smem *__smem;
>  /* Timeout (ms) for the trylock of remote spinlocks */
>  #define HWSPINLOCK_TIMEOUT	1000
>  
> +/* The qcom hwspinlock id is always plus one from the smem host id */
> +#define SMEM_HOST_ID_TO_HWSPINLOCK_ID(__x) ((__x) + 1)
> +
> +/**
> + * qcom_smem_bust_hwspin_lock_by_host() - bust the smem hwspinlock for an smem host id
> + * @host:	remote processor id
> + *
> + * Busts the hwspin_lock for the given smem host id. This helper is intended for remoteproc drivers
> + * that manage remoteprocs with an equivalent smem driver instance in the remote firmware. Drivers
> + * can force a release of the smem hwspin_lock if the rproc unexpectedly goes into a bad state.

Please wrap these at 80 characters.

> + *
> + * Context: Process context.
> + *
> + * Returns: 0 on success, otherwise negative errno.
> + */
> +int qcom_smem_bust_hwspin_lock_by_host(unsigned host)
> +{
> +	if (!__smem)
> +		return -EPROBE_DEFER;

This would be called at a time where -EPROBE_DEFER isn't appropriate,
the client should invoke qcom_smem_is_available() at probe time to guard
against this.

> +
> +	/* This function is for remote procs, so ignore SMEM_HOST_APPS */
> +	if (host == SMEM_HOST_APPS ||host >= SMEM_HOST_COUNT)

Missing <space> after ||

Regards,
Bjorn

> +		return -EINVAL;
> +
> +	return hwspin_lock_bust(__smem->hwlock, SMEM_HOST_ID_TO_HWSPINLOCK_ID(host));
> +}
> +EXPORT_SYMBOL_GPL(qcom_smem_bust_hwspin_lock_by_host);
> +
>  /**
>   * qcom_smem_is_available() - Check if SMEM is available
>   *
> diff --git a/include/linux/soc/qcom/smem.h b/include/linux/soc/qcom/smem.h
> index a36a3b9d4929..959eea0812bb 100644
> --- a/include/linux/soc/qcom/smem.h
> +++ b/include/linux/soc/qcom/smem.h
> @@ -14,4 +14,6 @@ phys_addr_t qcom_smem_virt_to_phys(void *p);
>  
>  int qcom_smem_get_soc_id(u32 *id);
>  
> +int qcom_smem_bust_hwspin_lock_by_host(unsigned host);
> +
>  #endif
> 
> -- 
> 2.25.1
>