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SubjectRe: [PATCH 11/14] fsi: Improve master indexing
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On 8/9/23 02:08, Joel Stanley wrote:
> On Mon, 12 Jun 2023 at 19:57, Eddie James <eajames@linux.ibm.com> wrote:
>> Master indexing is problematic if a hub is rescanned while the
>> root master is being rescanned. Move the IDA free below the device
>> unregistration, lock the scan mutex in the probe function, and
>> request a specific idx in the hub driver.
> I've applied this series, but taking a closer look at this patch I
> think it can be improved. If you resend, just send this patch.
>
>> Signed-off-by: Eddie James <eajames@linux.ibm.com>
>> ---
>> drivers/fsi/fsi-core.c | 41 ++++++++++++++++++++++--------------
>> drivers/fsi/fsi-master-hub.c | 2 ++
>> 2 files changed, 27 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c
>> index ec4d02264391..503061a6740b 100644
>> --- a/drivers/fsi/fsi-core.c
>> +++ b/drivers/fsi/fsi-core.c
>> @@ -1327,46 +1327,55 @@ static struct class fsi_master_class = {
>> int fsi_master_register(struct fsi_master *master)
>> {
>> int rc;
>> - struct device_node *np;
>>
>> mutex_init(&master->scan_lock);
>> - master->idx = ida_alloc(&master_ida, GFP_KERNEL);
>> +
>> + if (master->idx) {
> Why do we allocate a new idx if there's already one?


At this point, the master driver (aspeed, hub, i2cr, whatever) might
just be requesting a certain index. It's not allocated yet, so it needs
to be allocated so that we don't get overlap.


>
>> + master->idx = ida_alloc_range(&master_ida, master->idx,
>> + master->idx, GFP_KERNEL);
> If we can't get one in the range we want, we ask for any? Should this
> print a warning?


Perhaps, we could also return error here if we decide that the requested
index is needed and not just wanted.


>
>> + if (master->idx < 0)
>> + master->idx = ida_alloc(&master_ida, GFP_KERNEL);
>> + } else {
> If ixd was zero, we create one. This is the "normal" case?


Yes, the assumption is: zero is the default due to zero-alloc'd master
structures.


>
>> + master->idx = ida_alloc(&master_ida, GFP_KERNEL);
>> + }
>> +
> We check the same error condition again.


Yes I might be able to make this cleaner...


>
>> if (master->idx < 0)
>> return master->idx;
>> - dev_set_name(&master->dev, "fsi%d", master->idx);
>> + if (!dev_name(&master->dev))
>> + dev_set_name(&master->dev, "fsi%d", master->idx);
>> +
>> master->dev.class = &fsi_master_class;
>>
>> + mutex_lock(&master->scan_lock);
>> rc = device_register(&master->dev);
>> if (rc) {
>> ida_free(&master_ida, master->idx);
>> - return rc;
>> - }
>> + } else {
>> + struct device_node *np = dev_of_node(&master->dev);
> This change looks a bit different to the idx changes. What's happening here?


This is just restructuring to get the lock before the scan. It could be
a separate commit, yea.

Thanks for the review!

Eddie


>> - np = dev_of_node(&master->dev);
>> - if (!of_property_read_bool(np, "no-scan-on-init")) {
>> - mutex_lock(&master->scan_lock);
>> - fsi_master_scan(master);
>> - mutex_unlock(&master->scan_lock);
>> + if (!of_property_read_bool(np, "no-scan-on-init"))
>> + fsi_master_scan(master);
>> }
>>
>> - return 0;
>> + mutex_unlock(&master->scan_lock);
>> + return rc;
>> }
>> EXPORT_SYMBOL_GPL(fsi_master_register);
>>
>> void fsi_master_unregister(struct fsi_master *master)
>> {
>> - trace_fsi_master_unregister(master);
>> + int idx = master->idx;
>>
>> - if (master->idx >= 0) {
>> - ida_free(&master_ida, master->idx);
>> - master->idx = -1;
>> - }
>> + trace_fsi_master_unregister(master);
>>
>> mutex_lock(&master->scan_lock);
>> fsi_master_unscan(master);
>> + master->n_links = 0;
>> mutex_unlock(&master->scan_lock);
>> +
>> device_unregister(&master->dev);
>> + ida_free(&master_ida, idx);
>> }
>> EXPORT_SYMBOL_GPL(fsi_master_unregister);
>>
>> diff --git a/drivers/fsi/fsi-master-hub.c b/drivers/fsi/fsi-master-hub.c
>> index 6d8b6e8854e5..36da643b3201 100644
>> --- a/drivers/fsi/fsi-master-hub.c
>> +++ b/drivers/fsi/fsi-master-hub.c
>> @@ -12,6 +12,7 @@
>> #include <linux/slab.h>
>>
>> #include "fsi-master.h"
>> +#include "fsi-slave.h"
>>
>> #define FSI_ENGID_HUB_MASTER 0x1c
>>
>> @@ -229,6 +230,7 @@ static int hub_master_probe(struct device *dev)
>> hub->master.dev.release = hub_master_release;
>> hub->master.dev.of_node = of_node_get(dev_of_node(dev));
>>
>> + hub->master.idx = fsi_dev->slave->link + 1;
>> hub->master.n_links = links;
>> hub->master.read = hub_master_read;
>> hub->master.write = hub_master_write;
>> --
>> 2.31.1
>>

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