RE: [<RFC RESEND PATCH v2> 0/3] WriteBooster Feature Support

[Avri Altman <Avri.Altman@wdc.com>]

Hi,
The code looks good to me and I encourage you to submit your patches.
I just want to make some general remarks:
 - The way you use the clock scaling to set WB on/off, is IMO, an elegant design choice.
 - You should add a platform capability for WB
 - As for setting user space configuration options - I think you've got it wrong.
   You should read it from  bSupportedWriteBoosterBufferUserSpaceReductionTypes
   (offset 0x55 in the device descriptor).
   This is a configurable parameter that the chipset vendor control and can set during provisioning.
 - I agree with your approach toward flush during runtime suspend (keep-vcc-on):
    it is the host's interest to assist the device with some extra idle time if needed for WB flush.
    This way you will assure consistent write performance.

Thanks,
Avri

> 
> 
> Still a RFC patch, because I'm still expecting some comments
> on the design.
> 
> v1 -> v2:
> - Addressed comments on v1
> 
> - Supports shared buffer mode only
> 
> - Didn't use exception event as suggested.
>   The reason being while testing I saw that the WriteBooster
>   available buffer remains at 0x1 for a longer time if flush is
>   enabled all the time as compared to an event-based enablement.
>   This essentially means that writes go to the WriteBooster buffer
>   more. Spec says that the if flush is enabled, the device would
>   flush when it sees the command queue empty. So I guess that'd trigger
>   flush more than an event based approach.
>   Anyway the Vcc would be turned-off during system suspend, so flush
>   would stop anyway.
>   In this patchset, I never turn-off flush.
>   Hence the RFC.
> 
> Asutosh Das (3):
>   scsi: ufs: add write booster feature support
>   ufs-qcom: scsi: configure write booster type
>   ufs: sysfs: add sysfs entries for write booster
> 
>  drivers/scsi/ufs/ufs-qcom.c  |   7 ++
>  drivers/scsi/ufs/ufs-sysfs.c |  39 ++++++-
>  drivers/scsi/ufs/ufs.h       |  37 ++++++-
>  drivers/scsi/ufs/ufshcd.c    | 238
> ++++++++++++++++++++++++++++++++++++++++++-
>  drivers/scsi/ufs/ufshcd.h    |   9 ++
>  5 files changed, 324 insertions(+), 6 deletions(-)
> 
> --
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