Re: [PATCH v1 8/9] mmc: sdhci-cadence: add Cadence SD6HC support

[Kathpalia, Tanmay]

On 5/22/2026 11:02 AM, Adrian Hunter wrote:
> On 21/05/2026 20:28, Kathpalia, Tanmay wrote:
> > Hi Adrian,
> >
> > Thanks for your feedback.
> >
> > On 5/19/2026 8:59 PM, Adrian Hunter wrote:
> > > On 11/05/2026 23:21, Tanmay Kathpalia wrote:
> > > > The Cadence SD6HC is the sixth-generation SD Host Controller used in
> > > > Agilex5 SoCs. Its PHY differs substantially from the SD4HC: it
> > > > requires per-speed-mode IO cell timing parameters and a DLL-based
> > > > delay line to achieve correct signal margins across all speed grades
> > > > from Default Speed to HS400.
> > > >
> > > > Support is implemented in a new sdhci-cadence6.c alongside the
> > > > existing v4 code, now in sdhci-cadence4.c. Shared structures and the
> > > > v6 function interface are declared in a new sdhci-cadence.h header.
> > > > The common driver paths select between v4 and v6 PHY operations based
> > > > on the SDHCI specification version reported by the controller.
> > > >
> > > > The new compatible string "cdns,sd6hc" identifies SD6HC hardware in
> > > > device tree.
> > > >
> > > > Signed-off-by: Tanmay Kathpalia <tanmay.kathpalia@xxxxxxxxxx>
> > > > ---
> > > >    MAINTAINERS                                   |    7 +
> > > >    drivers/mmc/host/Makefile                     |    3 +-
> > > >    drivers/mmc/host/sdhci-cadence.h              |  113 ++
> > > >    .../{sdhci-cadence.c => sdhci-cadence4.c}     |   92 +-
> > > >    drivers/mmc/host/sdhci-cadence6.c             | 1051 +++++++++++++++++
> > > >    5 files changed, 1228 insertions(+), 38 deletions(-)
> > > >    create mode 100644 drivers/mmc/host/sdhci-cadence.h
> > > >    rename drivers/mmc/host/{sdhci-cadence.c => sdhci-cadence4.c} (91%)
> > > >    create mode 100644 drivers/mmc/host/sdhci-cadence6.c
> > > The new file names seem slightly misleading since sdhci-cadence4.c
> > > is the main driver as well as supporting V4, whereas sdhci-cadence6.c
> > > is most of V6 support.
> > >
> > > There doesn't seem much to gain from having a separate sdhci-cadence6.c.
> > > Isn't it simpler to just put it all in 1 source file.
> > I believe keeping them separate improves maintainability for the
> > following reasons:
> >
> > 1. V4 and V6 PHY programming models are fundamentally different:
> >      a. SD4HC reads pre-computed delay values directly from DT and
> >      writes them one-to-one into PHY registers.
> >      b. SD6HC takes only a few timing parameters (IO cell delay, delay
> >      element size) from DT and derives all PHY and SDHC register
> >      programming values inside the driver through a calibration
> >      sequence.
> > 2. The V6 PHY logic alone is more than 1000 lines. Merging it into
> > the existing file would make sdhci-cadence4.c significantly harder
> > to review, and maintain.
> > 3. Keep code structure aligned with U-Boot, where V6 handling is
> > also separated.
> >
> > That said, I am open to merging into one file if you think that is
> > better for maintainability in this driver. I can do that in v2.
> At the very least, the file names need to be more explicit:
>
>    The core part of the driver:	sdhci-cadence-core.c
>    The V6 PHY implementation:	sdhci-cadence-phy-v6.c

Ack. I will rename the files accordingly in V2.