Luca Coelho <luca@xxxxxxxxx> writes:
> From: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>
>
> The shared area is a DMA memory allocated in the host and
> mapped so that the host and the CSME firmware can
> exchange data. It is mapped through a dedicated PCI device
> that is driven by the mei bus driver.
>
> The bus driver is in charge of allocating and mapping this
> memory. It also needs to configure the CSME firmware with
> a specific set of commands, so that the CSME firmware will
> know that this memory is meant to be used by its internal
> WLAN module.
>
> For this, the CSME firmware first needs to completely
> initialize its WLAN module and only then get the mapping
> request.
>
> The problem is that the mei bus enumeration completes
> before the WLAN is completely ready. This means that
> the WLAN module's initialization is racing with iwlmei's
> allocation and mapping flow.
>
> Testing showed a problem in resume flows where iwlmei
> was too fast and the DMA mapping failed.
>
> Add a retry mechanism to make sure that we will succeed
> to map the memory.
>
> Fixes: 2da4366f9e2c ("iwlwifi: mei: add the driver to allow cooperation with CSME")
> Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx>
> Fixes: bcbddc4f9d02 ("iwlwifi: mei: wait before mapping the shared area")
I'll move the latter Fixes before s-o-b tag.
> - /*
> - * The CSME firmware needs to boot the internal WLAN client. Wait here
> - * so that the DMA map request will succeed.
> - */
> - msleep(20);
> + do {
> + ret = iwl_mei_alloc_shared_mem(cldev);
> + if (!ret)
> + break;
> + /*
> + * The CSME firmware needs to boot the internal WLAN client.
> + * This can take time in certain configurations (usually
> + * upon resume and when the whole CSME firmware is shut down
> + * during suspend).
> + *
> + * Wait a bit before retrying and hope we'll succeed next time.
> + */
>
> - ret = iwl_mei_alloc_shared_mem(cldev);
> - if (ret)
> + dev_dbg(&cldev->dev,
> + "Couldn't allocate the shared memory: %d, attempt %d / %d\n",
> + ret, alloc_retry, ALLOC_SHARED_MEM_RETRY_MAX_NUM);
> + msleep(100);
> + alloc_retry--;
> + } while (alloc_retry);
Nitpicking, but this could have been:
while (alloc_retry--);
But no need to resend because of this.
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