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SubjectRe: [PATCH v3 12/15] scsi: ufs: reduce the interrupts for power mode change requests
From
> 2015-09-02 19:13 GMT+09:00 Yaniv Gardi <ygardi@codeaurora.org>:
>> DME commands such as Hibern8 enter/exit and gear switch generate 2
>> completion interrupts, one for confirmation that command is received
>> by local UniPro and 2nd one is the final confirmation after
>> communication
>> with remote UniPro. Currently both of these completions are registered
>> as interrupt events which is not quite necessary and instead we can
>> just wait for the interrupt of 2nd completion, this should reduce
>> the number of interrupts and could reduce the unnecessary CPU wakeups
>> to handle extra interrupts.
>>
>> Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
>> Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>
>>
>> ---
>> drivers/scsi/ufs/ufshcd.c | 41
>> +++++++++++++++++++++++++++--------------
>> 1 file changed, 27 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>> index f2d4301..fc2a52d 100644
>> --- a/drivers/scsi/ufs/ufshcd.c
>> +++ b/drivers/scsi/ufs/ufshcd.c
>> @@ -986,13 +986,15 @@ ufshcd_wait_for_uic_cmd(struct ufs_hba *hba,
>> struct uic_command *uic_cmd)
>> * __ufshcd_send_uic_cmd - Send UIC commands and retrieve the result
>> * @hba: per adapter instance
>> * @uic_cmd: UIC command
>> + * @completion: initialize the completion only if this is set to true
>> *
>> * Identical to ufshcd_send_uic_cmd() expect mutex. Must be called
>> * with mutex held and host_lock locked.
>> * Returns 0 only if success.
>> */
>> static int
>> -__ufshcd_send_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd)
>> +__ufshcd_send_uic_cmd(struct ufs_hba *hba, struct uic_command *uic_cmd,
>> + bool completion)
>> {
>> if (!ufshcd_ready_for_uic_cmd(hba)) {
>> dev_err(hba->dev,
>> @@ -1000,7 +1002,8 @@ __ufshcd_send_uic_cmd(struct ufs_hba *hba, struct
>> uic_command *uic_cmd)
>> return -EIO;
>> }
>>
>> - init_completion(&uic_cmd->done);
>> + if (completion)
>> + init_completion(&uic_cmd->done);
>>
>> ufshcd_dispatch_uic_cmd(hba, uic_cmd);
>>
>> @@ -1025,7 +1028,7 @@ ufshcd_send_uic_cmd(struct ufs_hba *hba, struct
>> uic_command *uic_cmd)
>> ufshcd_add_delay_before_dme_cmd(hba);
>>
>> spin_lock_irqsave(hba->host->host_lock, flags);
>> - ret = __ufshcd_send_uic_cmd(hba, uic_cmd);
>> + ret = __ufshcd_send_uic_cmd(hba, uic_cmd, true);
>> spin_unlock_irqrestore(hba->host->host_lock, flags);
>> if (!ret)
>> ret = ufshcd_wait_for_uic_cmd(hba, uic_cmd);
>> @@ -2346,6 +2349,7 @@ static int ufshcd_uic_pwr_ctrl(struct ufs_hba
>> *hba, struct uic_command *cmd)
>> unsigned long flags;
>> u8 status;
>> int ret;
>> + bool reenable_intr = false;
>>
>> mutex_lock(&hba->uic_cmd_mutex);
>> init_completion(&uic_async_done);
>> @@ -2353,15 +2357,17 @@ static int ufshcd_uic_pwr_ctrl(struct ufs_hba
>> *hba, struct uic_command *cmd)
>>
>> spin_lock_irqsave(hba->host->host_lock, flags);
>> hba->uic_async_done = &uic_async_done;
>> - ret = __ufshcd_send_uic_cmd(hba, cmd);
>> - spin_unlock_irqrestore(hba->host->host_lock, flags);
>> - if (ret) {
>> - dev_err(hba->dev,
>> - "pwr ctrl cmd 0x%x with mode 0x%x uic error
>> %d\n",
>> - cmd->command, cmd->argument3, ret);
>> - goto out;
>> + if (ufshcd_readl(hba, REG_INTERRUPT_ENABLE) & UIC_COMMAND_COMPL)
>> {
>> + ufshcd_disable_intr(hba, UIC_COMMAND_COMPL);
>> + /*
>> + * Make sure UIC command completion interrupt is
>> disabled before
>> + * issuing UIC command.
>> + */
>> + wmb();
>> + reenable_intr = true;
>> }
>> - ret = ufshcd_wait_for_uic_cmd(hba, cmd);
>> + ret = __ufshcd_send_uic_cmd(hba, cmd, false);
>> + spin_unlock_irqrestore(hba->host->host_lock, flags);
>> if (ret) {
>> dev_err(hba->dev,
>> "pwr ctrl cmd 0x%x with mode 0x%x uic error
>> %d\n",
>> @@ -2387,7 +2393,10 @@ static int ufshcd_uic_pwr_ctrl(struct ufs_hba
>> *hba, struct uic_command *cmd)
>> }
>> out:
>> spin_lock_irqsave(hba->host->host_lock, flags);
>> + hba->active_uic_cmd = NULL;
>> hba->uic_async_done = NULL;
>> + if (reenable_intr)
>> + ufshcd_enable_intr(hba, UIC_COMMAND_COMPL);
>> spin_unlock_irqrestore(hba->host->host_lock, flags);
>> mutex_unlock(&hba->uic_cmd_mutex);
>>
>> @@ -3812,16 +3821,20 @@ static void ufshcd_sl_intr(struct ufs_hba *hba,
>> u32 intr_status)
>> */
>> static irqreturn_t ufshcd_intr(int irq, void *__hba)
>> {
>> - u32 intr_status;
>> + u32 intr_status, enabled_intr_status;
>> irqreturn_t retval = IRQ_NONE;
>> struct ufs_hba *hba = __hba;
>>
>> spin_lock(hba->host->host_lock);
>> intr_status = ufshcd_readl(hba, REG_INTERRUPT_STATUS);
>> + enabled_intr_status =
>> + intr_status & ufshcd_readl(hba, REG_INTERRUPT_ENABLE);
>
> Is it better to store interrupt mask to new member field in ufs_hba
> when ufshcd_{enable,disable}_intr() is called and avoid register
> read every interrupt? Because register read is much slower than
> normal memory read and we don't want to slow high IOPS workload.
>

Mita, this is a good idea, but it would require a little bit more
of code changing, which requires more testing to make sure no new issues
appear.
I would add this as a future note, but currently, i think there is no
major hit in performance. if you insist on changing it in this patch, it
might
delay the entire patch-set which i hope doesn't happen. do you agree?


>>
>> - if (intr_status) {
>> + if (intr_status)
>> ufshcd_writel(hba, intr_status, REG_INTERRUPT_STATUS);
>> - ufshcd_sl_intr(hba, intr_status);
>> +
>> + if (enabled_intr_status) {
>> + ufshcd_sl_intr(hba, enabled_intr_status);
>> retval = IRQ_HANDLED;
>> }
>> spin_unlock(hba->host->host_lock);
>> --
>> 1.8.5.2
>>
>> --
>> QUALCOMM ISRAEL, on behalf of Qualcomm Innovation Center, Inc. is a
>> member of Code Aurora Forum, hosted by The Linux Foundation
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>




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