Re: [PATCH v5 1/2] bus: mhi: core: Introduce internal register poll helper function

[Bhaumik Bhatt]

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@xxxxxxxxxxxxxx>
> > ---
> >  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