From: Sudeep Holla <sudeep.holla@arm.com>
To: Jassi Brar <jassisinghbrar@gmail.com>
Cc: Viresh Kumar <viresh.kumar@linaro.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Arnd Bergmann <arnd@arndb.de>, Rob Herring <robh+dt@kernel.org>,
Frank Rowand <frowand.list@gmail.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Devicetree List <devicetree@vger.kernel.org>,
Sudeep Holla <sudeep.holla@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] dt-bindings: mailbox: add doorbell support to ARM MHU
Date: Wed, 3 Jun 2020 19:31:20 +0100 [thread overview]
Message-ID: <20200603183120.GE23722@bogus> (raw)
In-Reply-To: <CABb+yY30nmbBUzYG62xGEbrr7107h_Edyq3jKPheZAQ0Cvr9Yg@mail.gmail.com>
On Mon, May 18, 2020 at 11:05:03PM -0500, Jassi Brar wrote:
> On Mon, May 18, 2020 at 10:40 PM Viresh Kumar <viresh.kumar@linaro.org> wrote:
> >
> > On 18-05-20, 18:29, Bjorn Andersson wrote:
> > > On Thu 14 May 22:17 PDT 2020, Viresh Kumar wrote:
> > > > This stuff has been doing rounds on the mailing list since several years
> > > > now with no agreed conclusion by all the parties. And here is another
> > > > attempt to get some feedback from everyone involved to close this once
> > > > and for ever. Your comments will very much be appreciated.
> > > >
> > > > The ARM MHU is defined here in the TRM [1] for your reference, which
> > > > states following:
> > > >
> > > > "The MHU drives the signal using a 32-bit register, with all 32
> > > > bits logically ORed together. The MHU provides a set of
> > > > registers to enable software to set, clear, and check the status
> > > > of each of the bits of this register independently. The use of
> > > > 32 bits for each interrupt line enables software to provide more
> > > > information about the source of the interrupt. For example, each
> > > > bit of the register can be associated with a type of event that
> > > > can contribute to raising the interrupt."
> > > >
> > >
> > > Does this mean that there are 32 different signals and they are all ORed
> > > into the same interrupt line to trigger software action when something
> > > happens?
> > >
> > > Or does it mean that this register is used to pass multi-bit information
> > > and when any such information is passed an interrupt will be triggered?
> > > If so, what does that information mean? How is it tied into other Linux
> > > drivers/subsystems?
> >
> > I have started to believe the hardware is written badly at this point
> > :)
> >
> H/W is actually fine :) Its just that the driver is written to
> _also_ support a platform (my original) that doesn't have shmem and
> need to pass data via 32bit registers.
> Frankly, I am not against the doorbell mode, I am against implementing
> two modes in a driver. If it really helped (note the past tense) the
> SCMI, we could implement the driver only in doorbell mode but
> unfortunately SCMI would still be _broken_ for non-doorbell
> controllers.
Should be fine as the specification is designed to work with only shmem
for any data transfer and mailbox is just a signal mechanism. I won't
be too worried about that.
--
Regards,
Sudeep
next prev parent reply other threads:[~2020-06-03 18:31 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-15 5:17 [RFC] dt-bindings: mailbox: add doorbell support to ARM MHU Viresh Kumar
2020-05-15 16:46 ` Jassi Brar
2020-05-18 7:35 ` Viresh Kumar
2020-05-19 0:53 ` Jassi Brar
2020-05-19 4:39 ` Viresh Kumar
2020-05-19 1:29 ` Bjorn Andersson
2020-05-19 3:40 ` Viresh Kumar
2020-05-19 4:05 ` Jassi Brar
2020-06-03 18:31 ` Sudeep Holla [this message]
2020-06-03 18:42 ` Jassi Brar
2020-06-03 18:28 ` Sudeep Holla
2020-05-28 19:20 ` Rob Herring
2020-05-29 4:07 ` Viresh Kumar
2020-06-03 18:04 ` Sudeep Holla
2020-06-03 18:17 ` Sudeep Holla
2020-06-04 5:59 ` Viresh Kumar
2020-06-04 8:28 ` Sudeep Holla
2020-06-03 18:32 ` Jassi Brar
2020-06-04 9:20 ` Sudeep Holla
2020-06-04 15:15 ` Jassi Brar
2020-06-05 4:56 ` Sudeep Holla
2020-06-05 6:30 ` Jassi Brar
2020-06-05 8:58 ` Sudeep Holla
2020-06-05 15:42 ` Jassi Brar
2020-06-10 9:33 ` Viresh Kumar
2020-06-11 10:00 ` Sudeep Holla
2020-06-12 0:34 ` Jassi Brar
2020-06-12 5:28 ` Viresh Kumar
2020-09-08 9:14 ` Arnd Bergmann
2020-09-08 9:27 ` Viresh Kumar
2020-09-08 13:26 ` Sudeep Holla
2020-09-09 3:23 ` Jassi Brar
2020-09-09 4:46 ` Viresh Kumar
2020-09-09 9:31 ` Sudeep Holla
2020-05-29 5:20 ` Jassi Brar
2020-05-29 6:27 ` Viresh Kumar
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