Messages in this thread | | | Date | Fri, 19 Feb 2021 10:05:54 -0800 | From | Bhaumik Bhatt <> | Subject | Re: [PATCH] bus: mhi: core: Move to polling method to wait for MHI ready |
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On 2021-02-19 06:55 AM, Jeffrey Hugo wrote: > On 2/18/2021 7:18 PM, Bhaumik Bhatt wrote: >> In certain devices, it is likely that there is no incoming MHI >> interrupt for a transition to MHI READY state. One such example >> is the move from Pass Through to an SBL or AMSS execution >> environment. In order to facilitate faster bootup times as there >> is no need to wait until timeout_ms completes, MHI host can poll >> every 25 milliseconds to check if device has entered MHI READY >> until a maximum timeout of twice the timeout_ms is reached. >> >> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org> >> --- >> drivers/bus/mhi/core/pm.c | 32 ++++++++++++++++---------------- >> 1 file changed, 16 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c >> index 65ebca8..ec0060c 100644 >> --- a/drivers/bus/mhi/core/pm.c >> +++ b/drivers/bus/mhi/core/pm.c >> @@ -9,6 +9,7 @@ >> #include <linux/dma-direction.h> >> #include <linux/dma-mapping.h> >> #include <linux/interrupt.h> >> +#include <linux/iopoll.h> >> #include <linux/list.h> >> #include <linux/mhi.h> >> #include <linux/module.h> >> @@ -157,30 +158,29 @@ int mhi_ready_state_transition(struct >> mhi_controller *mhi_cntrl) >> struct mhi_event *mhi_event; >> enum mhi_pm_state cur_state; >> struct device *dev = &mhi_cntrl->mhi_dev->dev; >> - u32 reset = 1, ready = 0; >> + u32 reset, ready; >> int ret, i; >> - /* Wait for RESET to be cleared and READY bit to be set by the >> device */ >> - wait_event_timeout(mhi_cntrl->state_event, >> - MHI_PM_IN_FATAL_STATE(mhi_cntrl->pm_state) || >> - mhi_read_reg_field(mhi_cntrl, base, MHICTRL, >> - MHICTRL_RESET_MASK, >> - MHICTRL_RESET_SHIFT, &reset) || >> - mhi_read_reg_field(mhi_cntrl, base, MHISTATUS, >> - MHISTATUS_READY_MASK, >> - MHISTATUS_READY_SHIFT, &ready) || >> - (!reset && ready), >> - msecs_to_jiffies(mhi_cntrl->timeout_ms)); >> - >> /* Check if device entered error state */ >> if (MHI_PM_IN_FATAL_STATE(mhi_cntrl->pm_state)) { >> dev_err(dev, "Device link is not accessible\n"); >> return -EIO; >> } >> - /* Timeout if device did not transition to ready state */ >> - if (reset || !ready) { >> - dev_err(dev, "Device Ready timeout\n"); >> + /* Wait for RESET to be cleared and READY bit to be set by the >> device */ >> + ret = readl_relaxed_poll_timeout(base + MHICTRL, reset, >> + !(reset & MHICTRL_RESET_MASK), 25000, >> + mhi_cntrl->timeout_ms * 1000); >> + if (ret) { >> + dev_err(dev, "Device failed to clear MHI Reset\n"); >> + return -ETIMEDOUT; >> + } >> + >> + ret = readl_relaxed_poll_timeout(base + MHISTATUS, ready, >> + (ready & MHISTATUS_READY_MASK), 25000, >> + mhi_cntrl->timeout_ms * 1000); >> + if (ret) { >> + dev_err(dev, "Device failed to enter MHI Ready\n"); >> return -ETIMEDOUT; >> } >> > > I think this gets a NACK from me. > > mhi_read_reg_field() uses the controller defined accessor method > read_reg(). readl_relaxed_poll_timeout() does not. If, say, MHI was > implemented over I2C, direct readl() accesses wouldn't be valid, and > this would break. > > Also, if the link ever goes down in the middle if the timeout, the > controller read_reg() should detect that, but > readl_relaxed_poll_timeout() would not. > > I'm fine with this concept, but I think the implementation needs to be > adjusted. I agree. I will think on this and plan it around the controller defined method.
Thanks, Bhaumik --- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
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