From: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
To: Joel Stanley <joel@jms.id.au>
Cc: devicetree <devicetree@vger.kernel.org>,
Ryan Chen <ryan_chen@aspeedtech.com>,
Andy Shevchenko <andriy.shevchenko@intel.com>,
Arnd Bergmann <arnd@arndb.de>, Andrew Jeffery <andrew@aj.id.au>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
OpenBMC Maillist <openbmc@lists.ozlabs.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
James Feist <james.feist@linux.intel.com>,
Vernon Mauery <vernon.mauery@linux.intel.com>,
Robin Murphy <robin.murphy@arm.com>,
Haiyue Wang <haiyue.wang@linux.intel.com>
Subject: Re: [PATCH v10 06/12] peci: Add a PECI adapter driver for Aspeed AST24xx/AST25xx
Date: Tue, 15 Jan 2019 15:36:43 -0800 [thread overview]
Message-ID: <17179a43-9ac7-366a-bfe6-044e80875a06@linux.intel.com> (raw)
In-Reply-To: <CACPK8XdBSYHB+S8Sp8Y=J0cK9D=coa+coQj3S7TEFs9DJ8Ljxg@mail.gmail.com>
On 1/15/2019 3:14 PM, Joel Stanley wrote:
> On Tue, 15 Jan 2019 at 09:49, Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> wrote:
>>>> + /**
>>>> + * We check that the regmap works on this very first access,
>>>> + * but as this is an MMIO-backed regmap, subsequent regmap
>>>> + * access is not going to fail and we skip error checks from
>>>> + * this point.
>>>
>>> Why do you use a regmap for this driver? AFAICT it has exclusive
>>> ownership over the register range it uses, which is sometimes a reason
>>> to use a regmap over a mmio region.
>>>
>>> I'm not sure if you've ever disassembled drivers/base/regmap/regmap.o,
>>> but if you do you will find that a single mmio read turns into
>>> hundreds of instructions.
>>>
>>
>> No specific reason. regmap makes some overhead as you mentioned but it
>> also provides some advantages on access simplification, endianness
>> handling and register dump at run time. I would not insist using of
>> regmap if you prefer using of raw readl and writel. Do you want replace
>> regmap with readl and writel in this driver?
>
> I think that would be best.
>
> You raise some good points about the regmap API, and you're not alone
> in using it for these reasons. We should look in to providing a
> suitable API without the overhead, or making regmap more efficient for
> the mmio case.
>
Okay. I'll rewrite this driver code using readl and writel instead of
regmap mmio. Thanks again for your review!
Regards,
Jae
next prev parent reply other threads:[~2019-01-15 23:36 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-07 21:41 [PATCH v10 00/12] PECI device driver introduction Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 01/12] dt-bindings: Add a document of PECI subsystem Jae Hyun Yoo
2019-01-14 5:34 ` Joel Stanley
2019-01-07 21:41 ` [PATCH v10 02/12] Documentation: ioctl: Add ioctl numbers for " Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 03/12] peci: Add support for PECI bus driver core Jae Hyun Yoo
2019-01-14 11:13 ` Joel Stanley
2019-01-14 22:38 ` Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 04/12] dt-bindings: Add a document of PECI adapter driver for ASPEED AST24xx/25xx SoCs Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 05/12] ARM: dts: aspeed: peci: Add PECI node Jae Hyun Yoo
2019-01-14 5:45 ` Joel Stanley
2019-01-14 22:12 ` Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 06/12] peci: Add a PECI adapter driver for Aspeed AST24xx/AST25xx Jae Hyun Yoo
2019-01-14 11:37 ` Joel Stanley
2019-01-14 22:49 ` Jae Hyun Yoo
2019-01-15 23:14 ` Joel Stanley
2019-01-15 23:36 ` Jae Hyun Yoo [this message]
2019-01-07 21:41 ` [PATCH v10 07/12] dt-bindings: mfd: Add a document for PECI client driver Jae Hyun Yoo
2019-01-14 11:39 ` Joel Stanley
2019-01-07 21:41 ` [PATCH v10 08/12] mfd: intel-peci-client: Add " Jae Hyun Yoo
2019-01-14 11:42 ` Joel Stanley
2019-01-14 23:03 ` Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 09/12] Documentation: hwmon: Add documents for PECI hwmon client drivers Jae Hyun Yoo
2019-01-14 11:43 ` Joel Stanley
2019-01-14 22:54 ` Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 10/12] hwmon: Add PECI cputemp driver Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 11/12] hwmon: Add PECI dimmtemp driver Jae Hyun Yoo
2019-01-07 21:41 ` [PATCH v10 12/12] Add maintainers for the PECI subsystem Jae Hyun Yoo
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