linux-kernel - Re: [PATCH v4 1/4] soc: mediatek: Refine scpsys to support multiple platform

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Date:	Mon, 15 Feb 2016 17:09:19 +0800
From:	James Liao <jamesjj.liao@...iatek.com>
To:	Matthias Brugger <matthias.bgg@...il.com>
CC:	Sascha Hauer <kernel@...gutronix.de>,
	Rob Herring <robh@...nel.org>,
	Kevin Hilman <khilman@...nel.org>,
	Daniel Kurtz <djkurtz@...omium.org>,
	<srv_heupstream@...iatek.com>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v4 1/4] soc: mediatek: Refine scpsys to support multiple
 platform

Hi Matthias,

On Wed, 2016-02-03 at 10:00 +0100, Matthias Brugger wrote:
> On 03/02/16 06:22, James Liao wrote:
> > On Tue, 2016-02-02 at 11:44 +0100, Matthias Brugger wrote:
> >> On 02/02/16 07:56, James Liao wrote:
> >>> On Sun, 2016-01-31 at 12:51 +0100, Matthias Brugger wrote:
> >>>>> On 20/01/16 07:08, James Liao wrote:
> >>>>>>> Refine scpsys driver common code to support multiple SoC / platform.
> >>>>>>>
> >>>>>>> Signed-off-by: James Liao<jamesjj.liao@...iatek.com>
> >>>>>>> ---
> >>>>>>>    drivers/soc/mediatek/mtk-scpsys.c | 418 ++++++++++++++++++++------------------
> >>>>>>>    drivers/soc/mediatek/mtk-scpsys.h |  55 +++++
> >>>>>>>    2 files changed, 270 insertions(+), 203 deletions(-)
> >>>>>>>    create mode 100644 drivers/soc/mediatek/mtk-scpsys.h
> >>>>>
> >>>>> In general this approach looks fine to me, comments below.
> >>>>>
> >>>>>>>
> >>>>>>> diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c
> >>>>>>> index 0221387..339adfc 100644
> >>>>>>> --- a/drivers/soc/mediatek/mtk-scpsys.c
> >>>>>>> +++ b/drivers/soc/mediatek/mtk-scpsys.c
> >>>>>>> @@ -11,29 +11,17 @@
> >>>>>>>     * GNU General Public License for more details.
> >>>>>>>     */
> >>>>>>>    #include <linux/clk.h>
> >>>>>>> -#include <linux/delay.h>
> >>>>>>> +#include <linux/init.h>
> >>>>>>>    #include <linux/io.h>
> >>>>>>> -#include <linux/kernel.h>
> >>>>>>>    #include <linux/mfd/syscon.h>
> >>>>>
> >>>>> When at it, do we need this include?
> >>> syscon_regmap_lookup_by_phandle() is declared in this head file.
> >>>
> >>>>>>> -#include <linux/init.h>
> >>>>>>>    #include <linux/of_device.h>
> >>>>>>>    #include <linux/platform_device.h>
> >>>>>>>    #include <linux/pm_domain.h>
> >>>>>>> -#include <linux/regmap.h>
> >>>>>>> -#include <linux/soc/mediatek/infracfg.h>
> >>>>>>>    #include <linux/regulator/consumer.h>
> >>>>>>> -#include <dt-bindings/power/mt8173-power.h>
> >>>>>>> +#include <linux/soc/mediatek/infracfg.h>
> >>>>>>> +
> >>>>>>> +#include "mtk-scpsys.h"
> >>>>>>>
> >>>>>>> -#define SPM_VDE_PWR_CON			0x0210
> >>>>>>> -#define SPM_MFG_PWR_CON			0x0214
> >>>>>>> -#define SPM_VEN_PWR_CON			0x0230
> >>>>>>> -#define SPM_ISP_PWR_CON			0x0238
> >>>>>>> -#define SPM_DIS_PWR_CON			0x023c
> >>>>>>> -#define SPM_VEN2_PWR_CON		0x0298
> >>>>>>> -#define SPM_AUDIO_PWR_CON		0x029c
> >>>>>>> -#define SPM_MFG_2D_PWR_CON		0x02c0
> >>>>>>> -#define SPM_MFG_ASYNC_PWR_CON		0x02c4
> >>>>>>> -#define SPM_USB_PWR_CON			0x02cc
> >>>>>
> >>>>> I would prefer to keep this defines and declare SoC specific ones where
> >>>>> necessary. It makes the code more readable.
> >>> Some register address may be reused by other modules among SoCs, so it's
> >>> not easy to maintain the defines when we implement multiple SoC drivers
> >>> in the same file. For example, offset 0x0298 is VEN2_PWR_CON on MT8173,
> >>> but it is MJC_PWR_CON on other chips.
> >>>
> >>
> >> So that sounds as if 0x0298 offset is MT8173 specific.
> >> I checked [VDE, MFG, VEN, IFR, ISP, DIS, DPY]_PWR_CON on mt8173, mt8135
> >> and mt6589 and they all have the same offset. So it doesn't seem as if
> >> the offset randomly changes for every SoC.
> >>
> >>> Furthermore, these register offsets are only used in scp_domain_data[],
> >>> and each element has its own power domain name. So I think it's enough
> >>> to know which power domain are using these registers and status bits.
> >>>
> >>
> >> Yes that's true, but it will make it easier for another person to
> >> understand the driver, especially if he want's to implement the driver
> >> for a new SoC.
> >
> > There are two kinds of conflicts may happen:
> >
> > 1. Different modules use the same register address.
> > 2. Different register addresses are used by the same module (on
> > different IC).
> >
> > Type 1. for example:
> >
> > 	#define SPM_BDP_PWR_CON			0x029c /* 2701 */
> > 	#define SPM_AUDIO_PWR_CON		0x029c /* 8173 */
> >
> > We can resolve this conflict easily, such as define these two register
> > name to the same register address.
> >
> > Type 2. for example:
> >
> > 	#define SPM_VDE_PWR_CON			0x0300 /* 6755 */
> > 	#define SPM_VDE_PWR_CON			0x0210 /* 8173 */
> >
> > We can not reuse the register defines in this case. We may need to name
> > the registers with its IC name, such as MT8173_SPM_VDE_PWR_CON and
> > MT6755_VDE_PWR_CON. But it will increase the maintain effort. That's why
> > I prefer to remove register defines if we implement multiple SoC's
> > scpsys in a single file.
> >
> >
> 
> Well type 2 for me is no problem at all. As stated in my last mail, 
> mt6755 would get the SoC name in the define (as a postfix preferably).
> I don't think that this will make a lot of pain regarding maintaining 
> it. Even less if we have the defines in alphabetic order.
> 
> I we see in the future that this converts to a mess, we always can get 
> rid of the defines quite easily.

OK, I'll add register names back in next patch.


Best regards,

James