On 29/08/2023 15:24, Bartosz Golaszewski wrote:
>>> +phys_addr_t qcom_shm_bridge_to_phys_addr(void *vaddr)
>>> +{
>>> + struct qcom_shm_bridge_chunk *chunk;
>>> + struct qcom_shm_bridge_pool *pool;
>>> +
>>> + guard(spinlock_irqsave)(&qcom_shm_bridge_chunks_lock);
>>> +
>>> + chunk = radix_tree_lookup(&qcom_shm_bridge_chunks,
>>> + (unsigned long)vaddr);
>>> + if (!chunk)
>>> + return 0;
>>> +
>>> + pool = chunk->parent;
>>> +
>>> + guard(spinlock_irqsave)(&pool->lock);
>>
>> Why both locks are spinlocks? The locks are used quite a lot.
>
> I'm not sure what to answer. The first one protects the global chunk
> mapping stored in the radix tree. The second one protects a single
> memory pool from concurrent access. Both can be modified from any
> context, hence spinlocks.
Not much PREEMPT friendly, although indeed protected code is small. At
least here, I did not check other places.
>
>>
>>> +
>>> + return gen_pool_virt_to_phys(pool->genpool, (unsigned long)vaddr);
>>> +}
>>> +EXPORT_SYMBOL_GPL(qcom_shm_bridge_to_phys_addr);
>>> +
>>> +static int qcom_shm_bridge_probe(struct platform_device *pdev)
>>> +{
>>> + struct qcom_shm_bridge_pool *default_pool;
>>> + struct device *dev = &pdev->dev;
>>> + int ret;
>>> +
>>> + /*
>>> + * We need to wait for the SCM device to be created and bound to the
>>> + * SCM driver.
>>> + */
>>> + if (!qcom_scm_is_available())
>>> + return -EPROBE_DEFER;
>>
>> I think we miss here (and in all other drivers) device links to qcm.
>>
>
> Well, SCM, once probed, cannot be unbound. What would device links
> guarantee above that?
Runtime PM, probe ordering (dependencies) detection.
>
>>> +
>>> + ret = qcom_scm_enable_shm_bridge();
>>> + if (ret)
>>> + return dev_err_probe(dev, ret,
>>> + "Failed to enable the SHM bridge\n");
>>> +
>>> + default_pool = qcom_shm_bridge_pool_new_for_dev(
>>> + dev, qcom_shm_bridge_default_pool_size);
>>> + if (IS_ERR(default_pool))
>>> + return dev_err_probe(dev, PTR_ERR(default_pool),
>>> + "Failed to create the default SHM Bridge pool\n");
>>> +
>>> + WRITE_ONCE(qcom_shm_bridge_default_pool, default_pool);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static const struct of_device_id qcom_shm_bridge_of_match[] = {
>>> + { .compatible = "qcom,shm-bridge", },
>>> + { }
>>> +};
>>> +
>>> +static struct platform_driver qcom_shm_bridge_driver = {
>>> + .driver = {
>>> + .name = "qcom-shm-bridge",
>>> + .of_match_table = qcom_shm_bridge_of_match,
>>> + /*
>>> + * Once enabled, the SHM Bridge feature cannot be disabled so
>>> + * there's no reason to ever unbind the driver.
>>> + */
>>> + .suppress_bind_attrs = true,
>>> + },
>>> + .probe = qcom_shm_bridge_probe,
>>> +};
>>> +
>>> +static int __init qcom_shm_bridge_init(void)
>>> +{
>>> + return platform_driver_register(&qcom_shm_bridge_driver);
>>> +}
>>> +subsys_initcall(qcom_shm_bridge_init);
>>
>> Why this is part of subsystem? Should be rather device_initcall... or
>> simply module (and a tristate).
>>
>
> We want it to get up as soon as possible (right after SCM, because SCM
> is the first user).
Then probably should be populated/spawned by SCM.
Best regards,
Krzysztof
