Re: [PATCH for rc] ufs: core: Configure MCQ after link startup

[Bart Van Assche <bvanassche@acm.org>]

On 12/18/25 11:32 PM, Peter Wang (王信友) wrote:
> It seems strange to me that ufshcd_mcq_enable is called before
> ufshcd_link_startup.
> 
> In driver development, configuration (config) should generally
> be done before enabling (enable) the hardware.
> Reason:
> Configuring first ensures the hardware operates correctly and
> avoids unexpected behavior or safety issues.
> 
> Typical steps:
> 1. Set registers/parameters
> 2. Initialize resources
> 3. Configure interrupts/DMA
> 4. Enable the hardware
> 
> So, do you also consider moving ufshcd_mcq_enable after
> ufshcd_config_mcq?

This has been considered but unfortunately the UFSHCI register set
definition makes this impossible. hba->host->can_queue must be set
before scsi_add_host() is called. hba->host->can_queue is derived
from the controller capabilities register (CAP). MCQ must be enabled
before NUTRS is extracted from the CAP register. Otherwise NUTRS is
reported as 32 - 1 instead of 64 - 1 (assuming that the host
controller supports 64 outstanding commands in MCQ mode).

Thanks,

Bart.