linux-kernel - Re: [RFC PATH 2/2] gpio: starfive-jh7100: Add StarFive JH7100 GPIO driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Mon, 26 Jul 2021 00:11:24 -0700
From:   Drew Fustini <drew@...gleboard.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Michael Walle <michael@...le.cc>, Rob Herring <robh+dt@...nel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Michael Zhu <michael.zhu@...rfivetech.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Fu Wei <tekkamanninja@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Huan Feng <huan.feng@...rfivetech.com>
Subject: Re: [RFC PATH 2/2] gpio: starfive-jh7100: Add StarFive JH7100 GPIO
 driver

On Fri, Jul 23, 2021 at 11:04:41PM +0200, Linus Walleij wrote:
> On Thu, Jul 1, 2021 at 8:39 AM Michael Walle <michael@...le.cc> wrote:
> > Am 2021-07-01 02:20, schrieb Drew Fustini:
> > > Add GPIO driver for the StarFive JH7100 SoC [1] used on the
> > > BeagleV Starlight JH7100 board [2].
> > >
> > > [1] https://github.com/starfive-tech/beaglev_doc/
> > > [2] https://github.com/beagleboard/beaglev-starlight
> > >
> > > Signed-off-by: Emil Renner Berthing <kernel@...il.dk>
> > > Signed-off-by: Huan Feng <huan.feng@...rfivetech.com>
> > > Signed-off-by: Drew Fustini <drew@...gleboard.org>
> >
> > Could this driver use GPIO_REGMAP and REGMAP_IRQ? See
> > drivers/gpio/gpio-sl28cpld.c for an example.
> 
> To me it looks just memory-mapped?
> 
> Good old gpio-mmio.c (select GPIO_GENERIC) should
> suffice I think.
> 
> Drew please look at drivers/gpio/gpio-ftgpio010.c for an example
> of GPIO_GENERIC calling bgpio_init() in probe().

Thank you for the suggestion. However, I am not sure that will work for
this SoC.

The GPIO registers are described in section 12 of JH7100 datasheet [1]
and I don't think they fit the expectation of gpio-mmio.c because there
is a seperate register for each GPIO line for output data value and
output enable.

There are 64 output data config registers which are 4 bytes wide. There
are 64 output enable config registers which are 4 bytes wide too. Output
data and output enable registers for a given GPIO pad are contiguous.
GPIO0_DOUT_CFG is 0x50 and GPIO0_DOEN_CFG is 0x54 while GPIO1_DOUT_CFG
is 0x58 and GPIO1_DOEN_CFG is 0x5C. The stride between GPIO pads is
effectively 8, which yields the formula: GPIOn_DOUT_CFG is 0x50+8n.
Similarly, GPIO0_DOEN_CFG is 0x54 and thus GPIOn_DOEN_CFG is 0x54+8n.

However, GPIO input data does use just one bit for each line. GPIODIN_0
at 0x48 covers GPIO[31:0] and GPIODIN_1 at 0x4c covers GPIO[63:32].

Thus the input could work with gpio-mmio but I am not sure how to
reconcile the register-per-gpio for the output value and output enable.

Is there way a way to adapt gpio-mmio for this situation?

Thanks,
Drew

[1] https://github.com/starfive-tech/beaglev_doc