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From: Sergei Shtylyov <>
To: Chris Brandt <>,
	Rob Herring <>,
	"" <>
Cc: Mark Rutland <>,
	"" <>,
	Philipp Zabel <>,
	Mason Yang <>,
	"" <>
Subject: Re: [PATCH RFC 0/2] Add Renesas RPC-IF support
Date: Wed, 11 Dec 2019 19:08:51 +0300	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>


On 12/11/2019 05:33 PM, Chris Brandt wrote:

>> Here's a set of 2 patches against Linus' repo. Renesas Reduced Pin Count
>> Interface (RPC-IF) allows a SPI flash or HyperFlash connected to the SoC to
>> be accessed via the external address space read mode or the manual mode.
> Looking at this driver, all it is are APIs. Meaning another driver is 
> needed to sit in between the MTD layer and this HW driver layer.

   Between the hardware and SPI, and between the hardware and HyperFlash
infrastructure. There's a lot of the common hardware code common between
these 2 driver areas.

> In the driver that I did, if the "RPC" HW is going to be used to control
> a SPI Flash device, it registered a spi controller and then the MTD 
> layer could access the device just like any other SPI controller driver. No
> additional drivers are needed.

   We're already been thru that with Mason's patch -- I don't want the code
duplicated between 2 drivers.

> Looking at the hyperbus driver that is in drivers/mtd/hyperbus/, it 
> seems that if the "RPC" HW is going to be used to control HyperFlash, then 

   Sure. But the code controlling RPC hardware is largely the same b/w 2 cases.

> all you would need to do is register a hyperbus controller using 
> hyperbus_register_device(). Then the MTD layer could read/write the flash using 
> normal MTD CFI interface.

   That's what I do (the current realization makes too many assumptions about
the HF hardware (both direct read and write). 

> Why do you think you need another layer in between the HW driver and the
> MTD layer?

   Because we don't want any duplicated code. Also, think about DT -- it
describes the hardware, not the driver configuration.

> Is your goal to make a multi-layered system where the HW jumps back and forth
> in between operating modes at runtime? I'm not sure of the use case for all of
> this.

   My goal is to prevent the code duplication (and keep DT sane too).

> Chris

MBR, Sergei

  reply	other threads:[~2019-12-11 16:08 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-10 19:34 [PATCH RFC 0/2] Add Renesas RPC-IF support Sergei Shtylyov
2019-12-10 19:37 ` [PATCH RFC 1/2] dt-bindings: memory: document Renesas RPC-IF bindings Sergei Shtylyov
2019-12-19 20:38   ` Rob Herring
2019-12-10 19:39 ` [PATCH RFC 2/2] memory: add Renesas RPC-IF driver Sergei Shtylyov
2019-12-11  9:58   ` Philipp Zabel
2020-02-10 10:21   ` Behme Dirk (CM/ESO2)
     [not found]     ` <5760bcdb-e44b-6f18-7262-9526684e5780-V5te9oGctAVWk0Htik3J/>
2020-02-22 20:42       ` Sergei Shtylyov
     [not found]         ` <5603f393-554d-e2a8-c2d8-6bafc20f4169-M4DtvfQ/>
2020-02-24  5:46           ` Behme Dirk (CM/ESO2)
     [not found]             ` <cba1e2ec-4896-23ef-ef7b-0f80d4310127-V5te9oGctAVWk0Htik3J/>
2020-02-24 17:28               ` Chris Brandt
2020-02-24 18:59             ` Sergei Shtylyov
2020-02-25  9:33               ` Behme Dirk (CM/ESO2)
     [not found]                 ` <3a182ac7-8d41-cdc7-2b87-7c503f68a426-V5te9oGctAVWk0Htik3J/>
2020-02-25 20:41                   ` Sergei Shtylyov
     [not found]                     ` <f21a9444-9541-6558-f5f5-ca0b733768ff-M4DtvfQ/>
2020-02-26  9:54                       ` Behme Dirk (CM/ESO2)
2020-02-27 20:32                         ` Sergei Shtylyov
2019-12-11 14:33 ` [PATCH RFC 0/2] Add Renesas RPC-IF support Chris Brandt
2019-12-11 16:08   ` Sergei Shtylyov [this message]
2019-12-11 16:20   ` Sergei Shtylyov

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