linux-kernel - Re: [PATCH v1 14/17] scsi: ufs: tune UniPro parameters to optimize hibern8 exit time

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Date:	Mon, 26 Oct 2015 14:32:45 -0000
From:	ygardi@...eaurora.org
To:	"Akinobu Mita" <akinobu.mita@...il.com>
Cc:	"Yaniv Gardi" <ygardi@...eaurora.org>,
	"Jej B" <james.bottomley@...senpartnership.com>,
	"Paul Bolle" <pebolle@...cali.nl>,
	"Christoph Hellwig" <hch@...radead.org>,
	"LKML" <linux-kernel@...r.kernel.org>,
	"linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	linux-arm-msm@...r.kernel.org, "Santosh Y" <santoshsy@...il.com>,
	linux-scsi-owner@...r.kernel.org,
	"Subhash Jadavani" <subhashj@...eaurora.org>,
	"Gilad Broner" <gbroner@...eaurora.org>,
	"Dolev Raviv" <draviv@...eaurora.org>,
	"Vinayak Holikatti" <vinholikatti@...il.com>,
	"James E.J. Bottomley" <jbottomley@...n.com>
Subject: Re: [PATCH v1 14/17] scsi: ufs: tune UniPro parameters to optimize
 hibern8 exit time

> 2015-09-13 23:52 GMT+09:00 Yaniv Gardi <ygardi@...eaurora.org>:
>> Optimal values of local UniPro parameters like PA_Hibern8Time &
>> PA_TActivate can help reduce the hibern8 exit latency. If both host and
>> device supports UniPro ver1.6 or later, these parameters will be
>> automatically tuned during link startup itself. But if either host or
>> device doesn't support UniPro ver 1.6 or later, we have to manually
>> tune them. But to keep manual tuning logic simple, we will only do
>> manual tuning if local unipro version doesn't support ver1.6 or later.
>>
>> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
>> Signed-off-by: Yaniv Gardi <ygardi@...eaurora.org>
>>
>> ---
>>  drivers/scsi/ufs/ufshcd.c | 121
>> ++++++++++++++++++++++++++++++++++++++++++++++
>>  drivers/scsi/ufs/ufshcd.h |   1 +
>>  drivers/scsi/ufs/ufshci.h |   2 +
>>  drivers/scsi/ufs/unipro.h |  21 ++++++++
>>  4 files changed, 145 insertions(+)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index a8659a9..0938d6c 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -596,6 +596,34 @@ static inline int ufshcd_is_hba_active(struct
>> ufs_hba *hba)
>>         return (ufshcd_readl(hba, REG_CONTROLLER_ENABLE) & 0x1) ? 0 : 1;
>>  }
>>
>> +u32 ufshcd_get_local_unipro_ver(struct ufs_hba *hba)
>> +{
>> +       /* HCI version 1.0 and 1.1 supports UniPro 1.41 */
>> +       if ((hba->ufs_version == UFSHCI_VERSION_10) ||
>> +           (hba->ufs_version == UFSHCI_VERSION_11))
>> +               return UFS_UNIPRO_VER_1_41;
>> +       else
>> +               return UFS_UNIPRO_VER_1_6;
>> +}
>> +EXPORT_SYMBOL(ufshcd_get_local_unipro_ver);
>> +
>> +static bool ufshcd_is_unipro_pa_params_tuning_req(struct ufs_hba *hba)
>> +{
>> +       /*
>> +        * If both host and device support UniPro ver1.6 or later, PA
>> layer
>> +        * parameters tuning happens during link startup itself.
>> +        *
>> +        * We can manually tune PA layer parameters if either host or
>> device
>> +        * doesn't support UniPro ver 1.6 or later. But to keep manual
>> tuning
>> +        * logic simple, we will only do manual tuning if local unipro
>> version
>> +        * doesn't support ver1.6 or later.
>> +        */
>> +       if (ufshcd_get_local_unipro_ver(hba) < UFS_UNIPRO_VER_1_6)
>> +               return true;
>> +       else
>> +               return false;
>> +}
>> +
>>  static void ufshcd_ungate_work(struct work_struct *work)
>>  {
>>         int ret;
>> @@ -4826,6 +4854,98 @@ out:
>>  }
>>
>>  /**
>> + * ufshcd_tune_pa_tactivate - Tunes PA_TActivate of local UniPro
>> + * @hba: per-adapter instance
>> + *
>> + * PA_TActivate parameter can be tuned manually if UniPro version is
>> less than
>> + * 1.61. PA_TActivate needs to be greater than or equal to peerM-PHY's
>> + * RX_MIN_ACTIVATETIME_CAPABILITY attribute. This optimal value can
>> help reduce
>> + * the hibern8 exit latency.
>> + *
>> + * Returns zero on success, non-zero error value on failure.
>> + */
>> +static int ufshcd_tune_pa_tactivate(struct ufs_hba *hba)
>> +{
>> +       int ret = 0;
>> +       u32 peer_rx_min_activatetime = 0, tuned_pa_tactivate;
>> +
>> +       if (!ufshcd_is_unipro_pa_params_tuning_req(hba))
>> +               return 0;
>
> This ufshcd_tune_pa_tactivate() is called only when
> ufshcd_is_unipro_pa_params_tuning_req() returns true.  Is this
> second check needed?
>


i could think of having this second check for any future call to
ufshcd_tune_pa_tactivate() which is not protected with a wrapping check
like in this case.
but i guess every call to ufshcd_tune_pa_tactivate()
will use ufshcd_tune_unipro_params() so we are good.
i will remove the 2nd check






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