Re: [PATCH] remoteproc: xlnx: reset virtio status during attach

["Shah, Tanmay" <tanmays@amd.com>]

On 9/30/2026 11:27 AM, Mathieu Poirier wrote:
> Hi,
> 
> On Thu, Sep 24, 2026 at 01:34:09PM -0700, Tanmay Shah wrote:
>> On AMD-Xilinx platforms cortex-A and cortex-R can be configured as
>> separate subsystems. In this case, both cores can boot independent of
>> each other. This is platform management firmware configuration to manage
> 
> I'm not sure to understand what the above sentence adds to the changelog.  I
> suggest either reworking or removing.
> 

Ack, I will remove it.

>> cores. In such a configuration, if Linux went through an uncontrolled
>> reboot during active rpmsg communication, then during next boot it can
>> find rpmsg virtio status not in the reset state. In such case it is
>> important to reset the virtio status during attach callback and wait
>> for the remote to handle virtio device reset. After reset, the remote
>> is expected to generate the notification to the host or the host will
>> eventually timeout and continue the normal boot flow.
>>
>> Assisted-by: LLM
>> Signed-off-by: Tanmay Shah <tanmay.shah@amd.com>
>> ---
>>  drivers/remoteproc/xlnx_r5_remoteproc.c | 74 +++++++++++++++++++++++++
>>  1 file changed, 74 insertions(+)
>>
>> diff --git a/drivers/remoteproc/xlnx_r5_remoteproc.c b/drivers/remoteproc/xlnx_r5_remoteproc.c
>> index 630621288430..6e7e2a5ea83c 100644
>> --- a/drivers/remoteproc/xlnx_r5_remoteproc.c
>> +++ b/drivers/remoteproc/xlnx_r5_remoteproc.c
>> @@ -6,6 +6,7 @@
>>  
>>  #include <linux/dma-mapping.h>
>>  #include <linux/firmware/xlnx-zynqmp.h>
>> +#include <linux/jiffies.h>
>>  #include <linux/kernel.h>
>>  #include <linux/mailbox_client.h>
>>  #include <linux/mailbox/zynqmp-ipi-message.h>
>> @@ -15,6 +16,7 @@
>>  #include <linux/of_reserved_mem.h>
>>  #include <linux/platform_device.h>
>>  #include <linux/remoteproc.h>
>> +#include <linux/wait.h>
>>  
>>  #include "remoteproc_internal.h"
>>  
>> @@ -33,6 +35,8 @@
>>  #define RSC_TBL_XLNX_MAGIC	((uint32_t)'x' << 24 | (uint32_t)'a' << 16 | \
>>  				 (uint32_t)'m' << 8 | (uint32_t)'p')
>>  
>> +#define RPROC_ATTACH_TIMEOUT_US (1000 * 1000)
>> +
> 
> Please see if you can use a kernel defined time constant instead of minting your
> own.
> 

Ack.

>>  /*
>>   * settings for RPU cluster mode which
>>   * reflects possible values of xlnx,cluster-mode dt-property
>> @@ -167,6 +171,9 @@ struct xlnx_rproc_crash_report {
>>   * @rsc_tbl_size: resource table size retrieved from remote
>>   * @pm_domain_id: RPU CPU power domain id
>>   * @ipi: pointer to mailbox information
>> + * @attach_wq: wait queue for attach-time vdev reset acknowledgment
> 
> I don't understand the explanation for @attach_wq - please rework.
> 
>> + * @waiting_for_attach_ack: whether attach is waiting for remote interrupt
>> + * @attach_ack: remote interrupt observed while attach wait is active
>>   */
>>  struct zynqmp_r5_core {
>>  	struct xlnx_rproc_crash_report *crash_report;
>> @@ -181,6 +188,9 @@ struct zynqmp_r5_core {
>>  	u32 rsc_tbl_size;
>>  	u32 pm_domain_id;
>>  	struct mbox_info *ipi;
>> +	wait_queue_head_t attach_wq;
>> +	bool waiting_for_attach_ack;
>> +	bool attach_ack;
>>  };
>>  
>>  /**
>> @@ -270,10 +280,17 @@ static void handle_event_notified(struct work_struct *work)
>>  static void zynqmp_r5_mb_rx_cb(struct mbox_client *cl, void *msg)
>>  {
>>  	struct zynqmp_ipi_message *ipi_msg, *buf_msg;
>> +	struct zynqmp_r5_core *r5_core;
>>  	struct mbox_info *ipi;
>>  	size_t len;
>>  
>>  	ipi = container_of(cl, struct mbox_info, mbox_cl);
>> +	r5_core = ipi->r5_core;
> 
> Is there really a chance that ipi->r5_core be NULL?
> 

Recently, INIT_WORK was moved before
mbox_request_channel_byname(mbox_cl, "rx"), In this case, if interrupt
occurs between requesting "rx" channel, and assigning r5_cores to ipi,
then r5_core can be NULL.

>> +
>> +	if (r5_core && READ_ONCE(r5_core->waiting_for_attach_ack)) {
>> +		WRITE_ONCE(r5_core->attach_ack, true);
> 
> Why use READ_ONCE/WRITE_ONCE here - what does it give you?
> 

I think this was added by AI agent, and I think it is to maintain atomic
nature of variable access. But if you prefer to protect these variables
via locks I will do that. These variables are shared between attach()
context and IPI interrupt, so I think they should be protected somehow.

>> +		wake_up(&r5_core->attach_wq);
>> +	}
> 
> If @rsc->status has been set to 0 in zynqmp_r5_attach() and an IPI is received
> before ->kick(), the core may erroneously think the remote processor is
> acknowleging the reset.
> 

Ack. Probably need to set these flags after kick(). I will do that.

>>  
>>  	/* copy data from ipi buffer to r5_core if IPI is buffered. */
>>  	ipi_msg = (struct zynqmp_ipi_message *)msg;
>> @@ -820,6 +837,62 @@ static int zynqmp_r5_get_rsc_table_va(struct zynqmp_r5_core *r5_core)
>>  
>>  static int zynqmp_r5_attach(struct rproc *rproc)
>>  {
>> +	struct zynqmp_r5_core *r5_core = rproc->priv;
>> +	struct device *dev = &rproc->dev;
>> +	bool wait_for_remote = false;
>> +	struct fw_rsc_vdev *rsc;
>> +	struct fw_rsc_hdr *hdr;
>> +	int i, offset, avail;
>> +	long time_left;
>> +
>> +	if (!rproc->table_ptr)
>> +		goto attach_success;
>> +
>> +	for (i = 0; i < rproc->table_ptr->num; i++) {
>> +		offset = rproc->table_ptr->offset[i];
>> +		hdr = (void *)rproc->table_ptr + offset;
>> +		avail = rproc->table_sz - offset - sizeof(*hdr);
>> +		rsc = (void *)hdr + sizeof(*hdr);
>> +
>> +		/* make sure table isn't truncated */
>> +		if (avail < 0) {
>> +			dev_err(dev, "rsc table is truncated\n");
>> +			return -EINVAL;
>> +		}
>> +
>> +		if (hdr->type != RSC_VDEV)
>> +			continue;
>> +
>> +		/*
>> +		 * reset vdev status, in case previous run didn't leave it in
>> +		 * a clean state.
>> +		 */
>> +		if (rsc->status) {
>> +			rsc->status = 0;
>> +			wait_for_remote = true;
>> +			break;
>> +		}
>> +	}
>> +
>> +	if (wait_for_remote) {
>> +		WRITE_ONCE(r5_core->attach_ack, false);
>> +		WRITE_ONCE(r5_core->waiting_for_attach_ack, true);
>> +	}
> 
> Again, I would like to understand the motivation behind using WRITE_ONCE()
> here...  I just don't see what kind of re-ordering issue you need to guard
> against.
> 

Ack. I will remove and introduce locks if that plan works.

>> +
>> +	/* kick remote to notify about attach */
>> +	rproc->ops->kick(rproc, 0);
> 
> Will older FW be able to deal with this properly?
> 
>> +
>> +	if (wait_for_remote) {
>> +		time_left = wait_event_timeout(r5_core->attach_wq,
>> +					       READ_ONCE(r5_core->attach_ack),
>> +					       usecs_to_jiffies(RPROC_ATTACH_TIMEOUT_US));
> 
> The condition where the driver is removed or the remoteproc shut down needs also
> needs to be handled as a break out condition.
> 

So this whole feature will be helpful only if linux gets rebooted
without proper cleanup. If driver is removed, it will call detach() via
zynqmp_cluster_exit(). If machine goes throug 'reboot' command, then the
driver has 'shutdown' callback registered which will call 'detach()'
operation. In these cases the remoteproc reset is guranteed and the
status will be 0 on next boot.

But if linux didn't get chance to execute above callbacks, only then the
status will be left non-zero on reboot.

> Thanks,
> Mathieu
> 
>> +		WRITE_ONCE(r5_core->waiting_for_attach_ack, false);
>> +
>> +		if (!time_left)
>> +			dev_warn(dev, "timeout waiting for remote vdev reset ack\n");
>> +	}
>> +
>> +attach_success:
>>  	dev_dbg(&rproc->dev, "rproc %d attached\n", rproc->index);
>>  
>>  	return 0;
>> @@ -920,6 +993,7 @@ static struct zynqmp_r5_core *zynqmp_r5_alloc_rproc_core(struct device *cdev)
>>  	r5_core = r5_rproc->priv;
>>  	r5_core->dev = cdev;
>>  	r5_core->np = dev_of_node(cdev);
>> +	init_waitqueue_head(&r5_core->attach_wq);
>>  	if (!r5_core->np) {
>>  		dev_err(cdev, "can't get device node for r5 core\n");
>>  		ret = -EINVAL;
>>
>> base-commit: 5f639b3018c0026a5341949724b4b921cf3a3d5d
>> -- 
>> 2.43.0
>>