Subject: Re: [PATCH v2 4/4] remoteproc/k3-dsp: Add support for L2RAM loading on C66x DSPs

From: Mathieu Poirier <[email-masked]>
Date: Tue, 2 Jun 2020 15:42:18 -0600

On Wed, May 20, 2020 at 07:10:06PM -0500, Suman Anna wrote:
> The resets for the DSP processors on K3 SoCs are managed through the
> Power and Sleep Controller (PSC) module. Each DSP typically has two
> resets - a global module reset for powering on the device, and a local
> reset that affects only the CPU while allowing access to the other
> sub-modules within the DSP processor sub-systems.
> 
> The C66x DSPs have two levels of internal RAMs that can be used to
> boot from, and the firmware loading into these RAMs require the
> local reset to be asserted with the device powered on/enabled using
> the module reset. Enhance the K3 DSP remoteproc driver to add support
> for loading into the internal RAMs. The local reset is deasserted on
> SoC power-on-reset, so logic has to be added in probe in remoteproc
> mode to balance the remoteproc state-machine.
> 
> Note that the local resets are a no-op on C71x cores, and the hardware
> does not supporting loading into its internal RAMs.
> 
> Signed-off-by: Suman Anna <[email-masked]>
> ---
> v2:
>  - Dropped the local-reset no-op checks from k3_dsp_rproc_prepare/unprepare()
>    callbacks. The logic will be adjusted back in the C71 patch series.
>  - The C71 local reset references are also removed from the comments for the
>    k3_dsp_rproc_prepare() function.
> v1: https://patchwork.kernel.org/patch/11458579/
> 
>  drivers/remoteproc/ti_k3_dsp_remoteproc.c | 72 +++++++++++++++++++++++
>  1 file changed, 72 insertions(+)
> 

Reviewed-by: Mathieu Poirier <[email-masked]>

> diff --git a/drivers/remoteproc/ti_k3_dsp_remoteproc.c b/drivers/remoteproc/ti_k3_dsp_remoteproc.c
> index e4036f5992fe..610fbbf85ee6 100644
> --- a/drivers/remoteproc/ti_k3_dsp_remoteproc.c
> +++ b/drivers/remoteproc/ti_k3_dsp_remoteproc.c
> @@ -174,6 +174,9 @@ static int k3_dsp_rproc_reset(struct k3_dsp_rproc *kproc)
>  		return ret;
>  	}
>  
> +	if (kproc->data->uses_lreset)
> +		return ret;
> +
>  	ret = kproc->ti_sci->ops.dev_ops.put_device(kproc->ti_sci,
>  						    kproc->ti_sci_id);
>  	if (ret) {
> @@ -191,6 +194,9 @@ static int k3_dsp_rproc_release(struct k3_dsp_rproc *kproc)
>  	struct device *dev = kproc->dev;
>  	int ret;
>  
> +	if (kproc->data->uses_lreset)
> +		goto lreset;
> +
>  	ret = kproc->ti_sci->ops.dev_ops.get_device(kproc->ti_sci,
>  						    kproc->ti_sci_id);
>  	if (ret) {
> @@ -198,6 +204,7 @@ static int k3_dsp_rproc_release(struct k3_dsp_rproc *kproc)
>  		return ret;
>  	}
>  
> +lreset:
>  	ret = reset_control_deassert(kproc->reset);
>  	if (ret) {
>  		dev_err(dev, "local-reset deassert failed, ret = %d\n", ret);
> @@ -209,6 +216,53 @@ static int k3_dsp_rproc_release(struct k3_dsp_rproc *kproc)
>  	return ret;
>  }
>  
> +/*
> + * The C66x DSP cores have a local reset that affects only the CPU, and a
> + * generic module reset that powers on the device and allows the DSP internal
> + * memories to be accessed while the local reset is asserted. This function is
> + * used to release the global reset on C66x DSPs to allow loading into the DSP
> + * internal RAMs. The .prepare() ops is invoked by remoteproc core before any
> + * firmware loading, and is followed by the .start() ops after loading to
> + * actually let the C66x DSP cores run.
> + */
> +static int k3_dsp_rproc_prepare(struct rproc *rproc)
> +{
> +	struct k3_dsp_rproc *kproc = rproc->priv;
> +	struct device *dev = kproc->dev;
> +	int ret;
> +
> +	ret = kproc->ti_sci->ops.dev_ops.get_device(kproc->ti_sci,
> +						    kproc->ti_sci_id);
> +	if (ret)
> +		dev_err(dev, "module-reset deassert failed, cannot enable internal RAM loading, ret = %d\n",
> +			ret);
> +
> +	return ret;
> +}
> +
> +/*
> + * This function implements the .unprepare() ops and performs the complimentary
> + * operations to that of the .prepare() ops. The function is used to assert the
> + * global reset on applicable C66x cores. This completes the second portion of
> + * powering down the C66x DSP cores. The cores themselves are only halted in the
> + * .stop() callback through the local reset, and the .unprepare() ops is invoked
> + * by the remoteproc core after the remoteproc is stopped to balance the global
> + * reset.
> + */
> +static int k3_dsp_rproc_unprepare(struct rproc *rproc)
> +{
> +	struct k3_dsp_rproc *kproc = rproc->priv;
> +	struct device *dev = kproc->dev;
> +	int ret;
> +
> +	ret = kproc->ti_sci->ops.dev_ops.put_device(kproc->ti_sci,
> +						    kproc->ti_sci_id);
> +	if (ret)
> +		dev_err(dev, "module-reset assert failed, ret = %d\n", ret);
> +
> +	return ret;
> +}
> +
>  /*
>   * Power up the DSP remote processor.
>   *
> @@ -352,6 +406,8 @@ static void *k3_dsp_rproc_da_to_va(struct rproc *rproc, u64 da, size_t len)
>  }
>  
>  static const struct rproc_ops k3_dsp_rproc_ops = {
> +	.prepare	= k3_dsp_rproc_prepare,
> +	.unprepare	= k3_dsp_rproc_unprepare,
>  	.start		= k3_dsp_rproc_start,
>  	.stop		= k3_dsp_rproc_stop,
>  	.kick		= k3_dsp_rproc_kick,
> @@ -614,6 +670,22 @@ static int k3_dsp_rproc_probe(struct platform_device *pdev)
>  		goto release_tsp;
>  	}
>  
> +	/*
> +	 * ensure the DSP local reset is asserted to ensure the DSP doesn't
> +	 * execute bogus code in .prepare() when the module reset is released.
> +	 */
> +	if (data->uses_lreset) {
> +		ret = reset_control_status(kproc->reset);
> +		if (ret < 0) {
> +			dev_err(dev, "failed to get reset status, status = %d\n",
> +				ret);
> +			goto release_mem;
> +		} else if (ret == 0) {
> +			dev_warn(dev, "local reset is deasserted for device\n");
> +			k3_dsp_rproc_reset(kproc);
> +		}
> +	}
> +
>  	ret = rproc_add(rproc);
>  	if (ret) {
>  		dev_err(dev, "failed to add register device with remoteproc core, status = %d\n",
> -- 
> 2.26.0
> 

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