linux-kernel - Re: [PATCH 04/20] bus: mhi: Cleanup the register definitions used in headers

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Date:   Thu, 3 Feb 2022 16:56:35 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Alex Elder <elder@...e.org>
Cc:     mhi@...ts.linux.dev, hemantk@...eaurora.org, bbhatt@...eaurora.org,
        quic_jhugo@...cinc.com, vinod.koul@...aro.org,
        bjorn.andersson@...aro.org, dmitry.baryshkov@...aro.org,
        skananth@...eaurora.org, vpernami@...eaurora.org,
        vbadigan@...eaurora.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/20] bus: mhi: Cleanup the register definitions used in
 headers

On Wed, Jan 05, 2022 at 06:23:52PM -0600, Alex Elder wrote:
> On 12/2/21 5:35 AM, Manivannan Sadhasivam wrote:
> > Cleanup includes:
> > 
> > 1. Moving the MHI register bit definitions to common.h header (only the
> >     register offsets differ between host and ep not the bit definitions)
> 
> The register offsets do differ, but the group of registers for the host
> differs from the group of registers for the endpoint by a fixed amount.
> (MHIREGLEN = 0x0000 for host, or 0x100 for endpoint; CRCBAP_LOWER is
> 0x0068 for host, 0x0168 for endpoint.)
> 
> In other words, can you instead use the same symbolic offsets, but
> have the endpoint add 0x0100 to them all?  It would make the fact
> that they're both referencing the same basic in-memory structure
> more obvious.
> 

Okay. I've used REG_ prefix for the register defines in common.h and used it on
host and ep internal.h.

> > 2. Using the GENMASK macro for masks
> > 3. Removing brackets for single values
> > 4. Using lowercase for hex values
> 
> Yay!!! For all three of the above.
> 
> More below.
> 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >   drivers/bus/mhi/common.h        | 129 ++++++++++++---
> >   drivers/bus/mhi/host/internal.h | 282 +++++++++++---------------------
> >   2 files changed, 207 insertions(+), 204 deletions(-)
> > 
> > diff --git a/drivers/bus/mhi/common.h b/drivers/bus/mhi/common.h
> > index 2ea438205617..c1272d61e54e 100644
> > --- a/drivers/bus/mhi/common.h
> > +++ b/drivers/bus/mhi/common.h
> > @@ -9,32 +9,123 @@
> >   #include <linux/mhi.h>
> > +/* MHI register bits */
> > +#define MHIREGLEN_MHIREGLEN_MASK		GENMASK(31, 0)
> > +#define MHIREGLEN_MHIREGLEN_SHIFT		0
> 
> Again, please eliminate all _SHIFT definitions where they define
> the low bit position of a mask.
> 
> Maybe you can add some underscores for readability?
> 
> Even if you don't do that, you could add a comment here or there to
> explain what certain abbreviations stand for, to make it easier to
> understand.  E.g., CHDB = channel doorbell, CCA = channel context
> array, BAP = base address pointer.
> 

I'll check on this.

Thanks,
Mani

> 					-Alex
> 
> 
> > +#define MHIVER_MHIVER_MASK			GENMASK(31, 0)
> > +#define MHIVER_MHIVER_SHIFT			0
> > +
> > +#define MHICFG_NHWER_MASK			GENMASK(31, 24)
> > +#define MHICFG_NHWER_SHIFT			24
> > +#define MHICFG_NER_MASK				GENMASK(23, 16)
> > +#define MHICFG_NER_SHIFT			16
> > +#define MHICFG_NHWCH_MASK			GENMASK(15, 8)
> > +#define MHICFG_NHWCH_SHIFT			8
> > +#define MHICFG_NCH_MASK				GENMASK(7, 0)
> > +#define MHICFG_NCH_SHIFT			0
> 
> . . .