Re: [PATCH v3 1/3] bus: mhi: core: Introduce internal register poll helper function

Bhaumik Bhatt
2021-03-10T22:58:06Z

On 2021-03-10 10:57 AM, Jeffrey Hugo wrote:
> On 2/23/2021 8:44 PM, 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..249ae26 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 = -ENOENT;
Make this 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 -EIO;
>
> I generally dislike recoding return codes. Do you believe it adds
> value here? I'm concerned that if I'm debugging an error, I'll get
> EIO, which I trace to here, but then I don't know what the actual
> error from mhi_read_reg_field() was.
>
Thanks for pointing out. I don't think its necessary to recode and I can
go back
to returning whatever the reg_field API returns. I have added the
proposed changes
here which help fix a potential bug that we'd return 0 if read is
successful but
polling fails.
>> +
>> + if (out == val)
>> + return 0;
>> +
>> + udelay(delayus);
>> + }
>> +
>> + return ret;
return -ENOENT; to signify failure to find the entry after poll duration
completes
>> +}
>> +
>> void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem
>> *base,
>> u32 offset, u32 val)
>> {
>>

Thanks,
Bhaumik
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