From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: gregkh <gregkh@linuxfoundation.org>,
smohanad@codeaurora.org, Jeffrey Hugo <jhugo@codeaurora.org>,
Kalle Valo <kvalo@codeaurora.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
hemantk@codeaurora.org,
linux-arm-msm <linux-arm-msm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 05/16] bus: mhi: core: Add support for ringing channel/event ring doorbells
Date: Thu, 23 Jan 2020 18:31:51 +0530 [thread overview]
Message-ID: <20200123130151.GD8937@mani> (raw)
In-Reply-To: <CAK8P3a1ACFdUdEywEQRAJ=HRYOp+0Y051ffNgAgqvSgjOEGyMA@mail.gmail.com>
On Thu, Jan 23, 2020 at 01:44:32PM +0100, Arnd Bergmann wrote:
> On Thu, Jan 23, 2020 at 1:01 PM Manivannan Sadhasivam
> <manivannan.sadhasivam@linaro.org> wrote:
> > On Thu, Jan 23, 2020 at 12:39:06PM +0100, Arnd Bergmann wrote:
> > > On Thu, Jan 23, 2020 at 12:19 PM Manivannan Sadhasivam
> > > <manivannan.sadhasivam@linaro.org> wrote:
> > >
> > > > +int __must_check mhi_read_reg(struct mhi_controller *mhi_cntrl,
> > > > + void __iomem *base, u32 offset, u32 *out)
> > > > +{
> > > > + u32 tmp = readl_relaxed(base + offset);
> > > ....
> > > > +void mhi_write_reg(struct mhi_controller *mhi_cntrl, void __iomem *base,
> > > > + u32 offset, u32 val)
> > > > +{
> > > > + writel_relaxed(val, base + offset);
> > >
> > > Please avoid using _relaxed accessors by default, and use the regular
> > > ones instead. There are a number of things that can go wrong with
> > > the relaxed version, so ideally each caller should have a comment
> > > explaining why this instance is safe without the barriers and why it
> > > matters to not have it.
> > >
> > > If there are performance critical callers of mhi_read_reg/mhi_write_reg,
> > > you could add mhi_read_reg_relaxed/mhi_write_reg_relaxed for those
> > > and apply the same rules there.
> > >
> > > Usually most mmio accesses are only needed for reconfiguration or
> > > other slow paths.
> > >
> >
> > Fair point. I'll defer to readl/writel APIs and I also need to add
> > le32_to_cpu/cpu_to_le32 to them.
>
> What do you need the byteswap for? All of the above already
> assume that the registers are little-endian.
>
I thought the readl/writel are native endian... Now I read the macro
definitions once again and looks like these APIs are LE for all archs...
So it is not needed. Sorry for the confusion.
Thanks,
Mani
> Arnd
next prev parent reply other threads:[~2020-01-23 13:02 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-23 11:18 [PATCH 00/16] Add MHI bus support Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 01/16] docs: Add documentation for MHI bus Manivannan Sadhasivam
2020-01-23 12:58 ` Arnd Bergmann
2020-01-23 13:10 ` Manivannan Sadhasivam
2020-01-23 13:19 ` Arnd Bergmann
2020-01-23 13:30 ` Manivannan Sadhasivam
2020-01-23 14:52 ` Jeffrey Hugo
2020-01-23 16:41 ` Jeffrey Hugo
2020-01-27 12:02 ` Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 02/16] bus: mhi: core: Add support for registering MHI controllers Manivannan Sadhasivam
2020-01-23 11:33 ` Greg KH
2020-01-23 11:56 ` Manivannan Sadhasivam
2020-01-23 17:05 ` Jeffrey Hugo
2020-01-23 18:14 ` Greg KH
2020-01-26 23:58 ` Jeffrey Hugo
2020-01-28 7:19 ` Manivannan Sadhasivam
2020-01-27 11:56 ` Manivannan Sadhasivam
2020-01-27 14:52 ` Jeffrey Hugo
2020-01-28 6:37 ` Manivannan Sadhasivam
2020-01-28 7:24 ` Greg KH
2020-01-28 7:27 ` Manivannan Sadhasivam
2020-01-24 8:29 ` Greg KH
2020-01-24 14:24 ` Jeffrey Hugo
2020-01-24 17:47 ` Greg KH
2020-01-24 18:12 ` Jeffrey Hugo
2020-01-25 13:26 ` Greg KH
2020-01-26 21:00 ` Jeffrey Hugo
2020-01-27 7:02 ` Manivannan Sadhasivam
2020-01-27 7:11 ` Greg KH
2020-01-23 11:18 ` [PATCH 03/16] bus: mhi: core: Add support for registering MHI client drivers Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 04/16] bus: mhi: core: Add support for creating and destroying MHI devices Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 05/16] bus: mhi: core: Add support for ringing channel/event ring doorbells Manivannan Sadhasivam
2020-01-23 11:39 ` Arnd Bergmann
2020-01-23 12:00 ` Manivannan Sadhasivam
2020-01-23 12:44 ` Arnd Bergmann
2020-01-23 13:01 ` Manivannan Sadhasivam [this message]
2020-01-23 14:44 ` Jeffrey Hugo
2020-01-24 22:51 ` Jeffrey Hugo
2020-01-25 13:46 ` Greg KH
2020-01-27 7:10 ` Manivannan Sadhasivam
2020-01-27 7:21 ` Greg KH
2020-01-23 11:18 ` [PATCH 06/16] bus: mhi: core: Add support for PM state transitions Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 07/16] bus: mhi: core: Add support for basic PM operations Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 08/16] bus: mhi: core: Add support for downloading firmware over BHIe Manivannan Sadhasivam
2020-01-28 19:36 ` Jeffrey Hugo
2020-01-29 6:56 ` Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 09/16] bus: mhi: core: Add support for downloading RDDM image during panic Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 10/16] bus: mhi: core: Add support for processing events from client device Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 11/16] bus: mhi: core: Add support for data transfer Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 12/16] bus: mhi: core: Add uevent support for module autoloading Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 13/16] MAINTAINERS: Add entry for MHI bus Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 14/16] net: qrtr: Add MHI transport layer Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 15/16] net: qrtr: Do not depend on ARCH_QCOM Manivannan Sadhasivam
2020-01-23 11:18 ` [PATCH 16/16] soc: qcom: Do not depend on ARCH_QCOM for QMI helpers Manivannan Sadhasivam
2020-01-23 11:45 ` Arnd Bergmann
2020-01-23 12:03 ` Manivannan Sadhasivam
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