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SubjectRe: [PATCH v5 1/2] bus: mhi: core: Introduce internal register poll helper function
Hi Mani,

On 2021-03-31 06:03 AM, Manivannan Sadhasivam wrote:
> On Mon, Mar 29, 2021 at 12:53:02PM -0700, Bhaumik Bhatt wrote:
>> Introduce helper function to allow MHI core driver to poll for
>> a value in a register field. This helps reach a common path to
>> read and poll register values along with a retry time interval.
>>
>> Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
>> ---
>> drivers/bus/mhi/core/internal.h | 3 +++
>> drivers/bus/mhi/core/main.c | 23 +++++++++++++++++++++++
>> 2 files changed, 26 insertions(+)
>>
>> diff --git a/drivers/bus/mhi/core/internal.h
>> b/drivers/bus/mhi/core/internal.h
>> index 6f80ec3..005286b 100644
>> --- a/drivers/bus/mhi/core/internal.h
>> +++ b/drivers/bus/mhi/core/internal.h
>> @@ -643,6 +643,9 @@ int __must_check mhi_read_reg(struct
>> mhi_controller *mhi_cntrl,
>> int __must_check mhi_read_reg_field(struct mhi_controller *mhi_cntrl,
>> void __iomem *base, u32 offset, u32 mask,
>> u32 shift, u32 *out);
>> +int __must_check mhi_poll_reg_field(struct mhi_controller *mhi_cntrl,
>> + void __iomem *base, u32 offset, u32 mask,
>> + u32 shift, u32 val, u32 delayus);
>> void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem
>> *base,
>> u32 offset, u32 val);
>> void mhi_write_reg_field(struct mhi_controller *mhi_cntrl, void
>> __iomem *base,
>> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
>> index 4e0131b..6f4b630 100644
>> --- a/drivers/bus/mhi/core/main.c
>> +++ b/drivers/bus/mhi/core/main.c
>> @@ -4,6 +4,7 @@
>> *
>> */
>>
>> +#include <linux/delay.h>
>> #include <linux/device.h>
>> #include <linux/dma-direction.h>
>> #include <linux/dma-mapping.h>
>> @@ -37,6 +38,28 @@ int __must_check mhi_read_reg_field(struct
>> mhi_controller *mhi_cntrl,
>> return 0;
>> }
>>
>> +int __must_check mhi_poll_reg_field(struct mhi_controller *mhi_cntrl,
>> + void __iomem *base, u32 offset,
>> + u32 mask, u32 shift, u32 val, u32 delayus)
>> +{
>> + int ret;
>> + u32 out, retry = (mhi_cntrl->timeout_ms * 1000) / delayus;
>> +
>> + while (retry--) {
>> + ret = mhi_read_reg_field(mhi_cntrl, base, offset, mask, shift,
>> + &out);
>> + if (ret)
>> + return ret;
>> +
>> + if (out == val)
>> + return 0;
>> +
>> + fsleep(delayus);
>> + }
>> +
>> + return -ENOENT;
>
> Maybe I'm too late on this one, but I don't think -ENOENT is the
> correct
> error code here. The error code will be returned only when the reg
> field
> value didn't change as expected, so in that case it should be -EINVAL
> or
> -ETIMEDOUT, no?
>
> Thanks,
> Mani
>

Thanks for pointing that out.

The intention of the error code was despite polling for whatever time
period,
we were unable to see the value changing as expected. I think the
-ETIMEDOUT
error code would be appropriate. Will upload a v6.

>> +}
>> +
>> void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem
>> *base,
>> u32 offset, u32 val)
>> {
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
>> Forum,
>> a Linux Foundation Collaborative Project
>>

Thanks,
Bhaumik
---
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
Forum,
a Linux Foundation Collaborative Project

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