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SubjectRe: [PATCH 1/3] bus: mhi: core: Handle syserr during power_up
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On 4/7/2020 12:26 AM, Manivannan Sadhasivam wrote:
> On Mon, Apr 06, 2020 at 03:04:35PM -0600, Jeffrey Hugo wrote:
>> The MHI device may be in the syserr state when we attempt to init it in
>> power_up(). Since we have no local state, the handling is simple -
>> reset the device and wait for it to transition out of the reset state.
>>
>> Signed-off-by: Jeffrey Hugo <jhugo@codeaurora.org>
>> ---
>> drivers/bus/mhi/core/pm.c | 20 ++++++++++++++++++++
>> 1 file changed, 20 insertions(+)
>>
>> diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
>> index 52690cb..cd6ba23 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>
>> @@ -760,6 +761,7 @@ static void mhi_deassert_dev_wake(struct mhi_controller *mhi_cntrl,
>>
>> int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
>> {
>> + enum mhi_state state;
>> enum mhi_ee_type current_ee;
>> enum dev_st_transition next_state;
>> struct device *dev = &mhi_cntrl->mhi_dev->dev;
>> @@ -829,6 +831,24 @@ int mhi_async_power_up(struct mhi_controller *mhi_cntrl)
>> goto error_bhi_offset;
>> }
>>
>> + state = mhi_get_mhi_state(mhi_cntrl);
>> + if (state == MHI_STATE_SYS_ERR) {
>> + mhi_set_mhi_state(mhi_cntrl, MHI_STATE_RESET);
>> + ret = readl_poll_timeout(mhi_cntrl->regs + MHICTRL, val,
>> + !(val & MHICTRL_RESET_MASK), 1000,
>
> Hmm. Do we really need a max 1ms delay between each read? I'd prefer to have
> 100ns to reduce the wait time.


I assume you mean 100us since that's the units of the parameter, and
usleep_range is the actual delay mechanism. Please correct me if that
is a bad assumption.

I chose 1ms to try to avoid flooding the bus, since on one system we
care about, the round trip time was observed to be ~1ms. However, that
is fairly arbitrary, so a factor of 10 reduction don't seem like a
significant issue.

>
>> + mhi_cntrl->timeout_ms * 1000);
>> + if (ret) {
>> + dev_info(dev, "Failed to reset syserr\n");
>
> dev_info(dev, "Failed to reset MHI due to syserr state\n"); ?
>

Ah yes, that is clearer. Thanks

--
Jeffrey Hugo
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

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