linux-kernel - Re: [PATCH] spi: intel: Update help text of PCI driver

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Date:   Thu, 9 Feb 2023 11:16:36 -0300
From:   Mauro Lima <mauro.lima@...ypsium.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:     broonie@...nel.org, michael@...le.cc, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spi: intel: Update help text of PCI driver

Hi Mika,

On Thu, Feb 9, 2023 at 2:39 AM Mika Westerberg
<mika.westerberg@...ux.intel.com> wrote:
>
> Hi,
>
> On Wed, Feb 08, 2023 at 02:52:53PM -0300, Mauro Lima wrote:
> > Modern intel hardware uses controllers that work in hardware
> > sequencing mode. In this mode, the controller exposes a subset
> > of operations, like read, write and erase, making it easier
> > and less error-prone for use.
> > On the other hand, most of the controllers handled by the
> > platform driver use software sequencing that exposes the
> > entire set of opcodes i.e. include the low-level operations
> > available from the controller.
> >
> > Since the PCI driver works with modern controllers, remove the
> > DANGEROUS tag from it.
> > Update the driver's help text and leave the DANGEROUS tag of
> > the platform driver.
>
> This is not done in this commit. You just update the help texts, right?
Yes, you are right, I will update it.

> > Signed-off-by: Mauro Lima <mauro.lima@...ypsium.com>
> > ---
> >  For the record of the base commit:
> >
> >  Given that the PCI driver handles controllers that only work with
> >  hardware sequencing, we can remove the dangerous tag.
> >  This patch is the second part of Mika's suggestion [1].
> >  The first part was accepted in [2].
> >
> >  [1] https://lore.kernel.org/r/Y1d9glOgHsQlZe2L@black.fi.intel.com/
> >  [2] https://lore.kernel.org/linux-spi/20230201205455.550308-1-mauro.lima@eclypsium.com/
> >
> >  This patch continues the work addressing the comments in the previous
> >  patch adding information about hardware and software sequencing.
> >  Discussion: https://lore.kernel.org/r/20230206183143.75274-1-mauro.lima@eclypsium.com/
> >
> >  drivers/spi/Kconfig | 21 +++++++++++++--------
> >  1 file changed, 13 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> > index 3a362c450cb6..9eb3c72d7cd8 100644
> > --- a/drivers/spi/Kconfig
> > +++ b/drivers/spi/Kconfig
> > @@ -454,13 +454,16 @@ config SPI_INTEL_PCI
> >       select SPI_INTEL
> >       help
> >         This enables PCI support for the Intel PCH/PCU SPI controller in
> > -       master mode. This controller is present in modern Intel hardware
> > -       and is used to hold BIOS and other persistent settings. This
> > -       driver only supports hardware sequencing mode. Using this
> > -       driver it is possible to upgrade BIOS directly from Linux.
> > +       master mode. This controller is used to hold BIOS and other
> > +       persistent settings. Controllers present in modern Intel hardware
> > +       only work in hardware sequencing mode, this means that the
> > +       controller exposes a subset of operations that makes it easier
> > +       and safer to use. Using this driver it is possible to upgrade BIOS
>
> I would remove the "easier" part because from user perspective there is
> really no difference.
Will do, thanks.

> > +       directly from Linux.
> >
> > -       Say N here unless you know what you are doing. Overwriting the
> > -       SPI flash may render the system unbootable.
> > +       Say N here unless you want to overwrite the flash memory and
>
> Putting it like this surely scares all distro folks from ever enabling
> this ;-)
>
>   "Say N here unless you want to overwrite the flash memory.."
>
> At least to me this means that if you enable this option your flash
> memory will be overwritten.
Do you have a suggestion for the "Say N here" text? Maybe remove it
since this is safe for use now? I found it difficult to rephrase it

> > +       know what you are doing or you want to read the memory's content.
> > +       Overwriting the SPI flash may render the system unbootable.
> >
> >         To compile this driver as a module, choose M here: the module
> >         will be called spi-intel-pci.
> > @@ -473,8 +476,10 @@ config SPI_INTEL_PLATFORM
> >       help
> >         This enables platform support for the Intel PCH/PCU SPI
> >         controller in master mode that is used to hold BIOS and other
> > -       persistent settings. Most of these controllers are using
> > -       software sequencing mode. Using this driver it is possible to
> > +       persistent settings. Most of these controllers work in
> > +       software sequencing mode, which means that the controller
> > +       exposes the full set of operations that supports, making it
> > +       more complex for use. Using this driver it is possible to
>
> Here,
>
> exposes the low level SPI-NOR opcodes to the software
Ok
>
> I think is better. Also here too drop the "complex" as it looks similar
> from user perspective.
I agree
> >         upgrade BIOS directly from Linux.
> >
> >         Say N here unless you know what you are doing. Overwriting the
> >
> > base-commit: 7db738b5fea4533fa217dfb05c506c15bd0964d9
> > --
> > 2.39.1

Thanks