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

[James Liao <jamesjj.liao-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>]

Hi Matthias,

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-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
> >>> > >---
> >>> > >   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.


Best regards,

James


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