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SubjectRe: [PATCH v3 4/7] bus: mhi: core: Add support to stop or start channel data transfers
On 2020-12-02 04:33 PM, Hemant Kumar wrote:
> Hi Bhaumik,
>
> On 12/2/20 3:40 PM, Bhaumik Bhatt wrote:
>> Some MHI client drivers may want to request a pause or halt of
>> data transfer activity on their channels. Support for this does
>> not exist and must be introduced, wherein the channel context is
>> not reset or cleared but only the STOP channel command is issued.
>> This would need to be paired with an API that allows resuming the
>> data transfer activity on channels by use of the START channel
>> command. This API assumes that the context information is already
>
> is it a better option to make sure channel context is setup as this is
> an exported API. Hence check for channel context bail out in case
> channel context is not setup with an err msg ?
>
This is a better method, yes. Addressed in v4.
>> setup. Enable this using two new APIs, mhi_start_transfer() and
>> mhi_stop_transfer().
>>
>> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
>> ---
>> drivers/bus/mhi/core/main.c | 41
>> +++++++++++++++++++++++++++++++++++++++++
>> include/linux/mhi.h | 19 +++++++++++++++++++
>> 2 files changed, 60 insertions(+)
>>
>> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
>> index 4cc5ced..2e4b34a 100644
>> --- a/drivers/bus/mhi/core/main.c
>> +++ b/drivers/bus/mhi/core/main.c
>> @@ -1552,6 +1552,47 @@ void mhi_unprepare_from_transfer(struct
>> mhi_device *mhi_dev)
>> }
>> EXPORT_SYMBOL_GPL(mhi_unprepare_from_transfer);
>> +static int mhi_update_transfer_state(struct mhi_device *mhi_dev,
>> + enum mhi_ch_state_type to_state)
>> +{
>> + struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
>> + struct mhi_chan *mhi_chan;
>> + int dir, ret;
>> +
>> + for (dir = 0; dir < 2; dir++) {
>> + mhi_chan = dir ? mhi_dev->ul_chan : mhi_dev->dl_chan;
>> +
>> + if (!mhi_chan)
>> + continue;
>> +
>> + /*
>> + * Bail out if one of the channels fail as client will reset
>> + * both upon failure
>> + */
>> + mutex_lock(&mhi_chan->mutex);
>> + ret = mhi_update_channel_state(mhi_cntrl, mhi_chan, to_state);
>> + if (ret) {
>> + mutex_unlock(&mhi_chan->mutex);
>> + return ret;
>> + }
>> + mutex_unlock(&mhi_chan->mutex);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +int mhi_stop_transfer(struct mhi_device *mhi_dev)
>> +{
>> + return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_STOP);
>> +}
>> +EXPORT_SYMBOL_GPL(mhi_stop_transfer);
>> +
>> +int mhi_start_transfer(struct mhi_device *mhi_dev)
>> +{
>> + return mhi_update_transfer_state(mhi_dev, MHI_CH_STATE_TYPE_START);
>> +}
>> +EXPORT_SYMBOL_GPL(mhi_start_transfer);
>> +
>> int mhi_poll(struct mhi_device *mhi_dev, u32 budget)
>> {
>> struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
>> diff --git a/include/linux/mhi.h b/include/linux/mhi.h
>> index aa9757e..35779a0 100644
>> --- a/include/linux/mhi.h
>> +++ b/include/linux/mhi.h
>> @@ -704,6 +704,25 @@ int mhi_prepare_for_transfer(struct mhi_device
>> *mhi_dev);
>> void mhi_unprepare_from_transfer(struct mhi_device *mhi_dev);
>> /**
>> + * mhi_stop_transfer - Pauses ongoing channel activity by issuing the
>> STOP
>> + * channel command to both UL and DL channels.
>> This command
>> + * does not reset the channel context and the
>> client drivers
>> + * can issue mhi_start_transfer to resume
>> activity.
>> + * @mhi_dev: Device associated with the channels
>> + */
>> +int mhi_stop_transfer(struct mhi_device *mhi_dev);
>> +
>> +/**
>> + * mhi_start_transfer - Resumes channel activity by issuing the START
>> channel
>> + * command to both UL and DL channels. This
>> command assumes
>> + * the channel context is already setup and the
>> client
>> + * drivers can issue mhi_stop_transfer to pause
>> activity if
>> + * required.
>> + * @mhi_dev: Device associated with the channels
>> + */
>> +int mhi_start_transfer(struct mhi_device *mhi_dev);
>> +
>> +/**
>> * mhi_poll - Poll for any available data in DL direction
>> * @mhi_dev: Device associated with the channels
>> * @budget: # of events to process
>>
> Overall change looks good.
>
> Thanks,
> Hemant

Thanks,
Bhaumik
---
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Forum,
a Linux Foundation Collaborative Project

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