Re: [PATCH V3] ARM: tegra: Define Tegra20 CAR binding

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Hi Stephen,

On Wed, Feb 15, 2012 at 1:30 PM, Stephen Warren <swarren@xxxxxxxxxx> wrote:
> Simon Glass wrote at Wednesday, February 15, 2012 1:25 PM:
>> On Wed, Feb 15, 2012 at 11:14 AM, Stephen Warren <swarren@xxxxxxxxxx> wrote:
>> > Simon Glass wrote at Wednesday, February 15, 2012 11:45 AM:
>> >> On Wed, Feb 15, 2012 at 10:14 AM, Stephen Warren <swarren@xxxxxxxxxx> wrote:
>> >> > The Tegra20 CAR (Clock And Reset) Controller controls most aspects of
>> >> > most clocks within Tegra20. The device tree binding models this as a
>> >> > single monolithic clock provider, which exports ~130 clocks. This reduces
>> >> > the number of nodes needed in device tree to represent these clocks.
>> >> >
>> >> > This binding is only useful for Tegra20; the set of clocks that exists on
>> >> > Tegra30 is sufficiently different to merit its own binding.
>> >>
>> >> It seems there is a large common element - they are almost backwards
>> >> compatible. Should we not at least look at this now?
>> >
>> > I don't believe there's any need for the clock IDs for the two chips to
>> > align in any way. These are two different chips, with different sets of
>> > clocks, different tegra*.dtsi files, different clock "drivers" that define
>> > the available clocks, etc.
>> >
>> > And while as you say, there are a lot of similarities, there are also a
>> > number of differences within these first 96 clocks which make having
>> > things completely aligned impractical. I imagine you'd rather that
>> > Tegra30's binding follow Tegra30's CLK_OUT_ENB register layouts exactly,
>> > rather than attempting to align with Tegra20 even in the face of
>> > differences in HW.
>>
>> OK my question was really more about how you deal with multi-arch in
>> Linux / U-Boot. Does it make sense to ignore the commonality. Perhaps
>> instead the range from 96 to 160 should be reserved?
>
> I'm having a hard time seeing the problem here; the correct mapping from
> device tree clock ID values to clock objects will be selected based on
> the SoC version you're running on; there's no need to try and tie the
> clock IDs for the two SoCs together, and there's always a way to know
> which SoC version's numbering you should be dealing with at runtime.

At present in U-Boot we have exactly the same clock code for T20 and
T30, and the header file differences are in the reserved bits. I am
pointing this out in case it is of interest. But I think you are aware
of it, so please go ahead with the binding as you have it. So:

Acked-by: Simon Glass <sjg@xxxxxxxxxxxx>


diff -u ./arch/arm/include/asm/arch-tegra2/clock-tables.h
./arch/arm/include/asm/arch-tegra3/clock-tables.h
 /* The clocks supported by the hardware */
 enum periph_id {
 	PERIPH_ID_FIRST,
 	PERIPH_ID_CPU = PERIPH_ID_FIRST,
-	PERIPH_ID_RESERVED1,
-	PERIPH_ID_RESERVED2,
-	PERIPH_ID_AC97,
-	PERIPH_ID_RTC,
+	PERIPH_ID_COP,
+	PERIPH_ID_TRIGSYS,
+	PERIPH_ID_RESERVED3,
+	PERIPH_ID_RESERVED4,
 	PERIPH_ID_TMR,
 	PERIPH_ID_UART1,
 	PERIPH_ID_UART2,
@@ -50,7 +53,7 @@
 	PERIPH_ID_SDMMC4,

 	/* 16 */
-	PERIPH_ID_TWC,
+	PERIPH_ID_RESERVED16,
 	PERIPH_ID_PWM,
 	PERIPH_ID_I2S2,
 	PERIPH_ID_EPP,
@@ -61,12 +64,12 @@

 	/* 24 */
 	PERIPH_ID_3D,
-	PERIPH_ID_IDE,
+	PERIPH_ID_RESERVED24,
 	PERIPH_ID_DISP2,
 	PERIPH_ID_DISP1,
 	PERIPH_ID_HOST1X,
 	PERIPH_ID_VCP,
-	PERIPH_ID_RESERVED30,
+	PERIPH_ID_I2S0,
 	PERIPH_ID_CACHE2,

 	/* Middle word: 63:32 */
@@ -83,9 +86,9 @@
 	PERIPH_ID_KFUSE,
 	PERIPH_ID_SBC1,
 	PERIPH_ID_SNOR,
-	PERIPH_ID_SPI1,
+	PERIPH_ID_RESERVED43,
 	PERIPH_ID_SBC2,
-	PERIPH_ID_XIO,
+	PERIPH_ID_RESERVED45,
 	PERIPH_ID_SBC3,
 	PERIPH_ID_DVC_I2C,

@@ -122,17 +125,17 @@
 	/* 72 */
 	PERIPH_ID_AFI,
 	PERIPH_ID_CORESIGHT,
-	PERIPH_ID_RESERVED74,
+	PERIPH_ID_PCIEXCLK,
 	PERIPH_ID_AVPUCQ,
 	PERIPH_ID_RESERVED76,
 	PERIPH_ID_RESERVED77,
 	PERIPH_ID_RESERVED78,
-	PERIPH_ID_RESERVED79,
+	PERIPH_ID_DTV,

 	/* 80 */
-	PERIPH_ID_RESERVED80,
-	PERIPH_ID_RESERVED81,
-	PERIPH_ID_RESERVED82,
+	PERIPH_ID_NANDSPEED,
+	PERIPH_ID_I2CSLOW,
+	PERIPH_ID_DSIB,
 	PERIPH_ID_RESERVED83,
 	PERIPH_ID_IRAMA,
 	PERIPH_ID_IRAMB,
@@ -141,7 +144,76 @@

 	/* 88 */
 	PERIPH_ID_CRAM2,
...extra T30 things

Regards,
Simon

>
> --
> nvpublic
>
--
To unsubscribe from this list: send the line "unsubscribe linux-tegra" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[ARM Kernel]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Photo]     [Yosemite News]    [Yosemite Photos]     [Free Online Dating]     [Linux Kernel]     [Linux SCSI]     [XFree86]

Add to Google Powered by Linux