Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Jon Hunter]

On 10/15/2012 02:16 PM, Richard Cochran wrote:
> From: hvaibhav@ti.com <hvaibhav@ti.com>
> 
> With recent changes in omap gpmc driver code, in case of DT
> boot mode, where bootloader does not configure gpmc cs space
> will result into kernel BUG() inside gpmc_mem_init() function,
> as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
> gpmc_config7[0].baseaddress is set to '0' on reset.

I am not sure I completely follow the logic here.

Won't this problem occur if the bootloader does not configure the gpmc
cs space AND we are not using DT?

Is the csvalid bit set because we are booting from the internal ROM?

I guess I don't see why csvalid bit being set and a base-address of 0x0
should not be allowed. That should be a valid combination.

One problem I see with gpmc_mem_init() is that it assumes that
BOOT_ROM_SPACE is 1MB for all devices starting at 0x0 apart from the
apollon board. For newer devices such as OMAP4, there is only 48KB of
internal ROM and only mapped to 0x0 when booting from internal ROM. So
this needs to be fixed.

How much internal ROM does the AM335x have and where is it mapped?

> This use-case is applicable for any board/EVM which doesn't have
> any peripheral connected to gpmc cs0, for example BeagleXM and
> BeagleBone, so DT boot mode fails.
> 
> This patch adds of_have_populated_dt() check before creating
> device, so that for DT boot mode, gpmc probe will not be called
> which is expected behavior, as gpmc is not supported yet from DT.

Yes, but we do actually still allow some platform devices to be probed
(such as dmtimers) when booting with DT that don't support DT yet. So
this change prevents us from using the gpmc on boards when booting with DT.

I am not convinced that this is addressing the underlying problem with
gpmc_mem_init().

Cheers
Jon

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Jon Hunter]

Hi Tony,

On 10/16/2012 12:48 PM, Tony Lindgren wrote:
> * Richard Cochran <richardcochran@gmail.com> [121015 12:18]:
>> From: hvaibhav@ti.com <hvaibhav@ti.com>
>>
>> With recent changes in omap gpmc driver code, in case of DT
>> boot mode, where bootloader does not configure gpmc cs space
>> will result into kernel BUG() inside gpmc_mem_init() function,
>> as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
>> gpmc_config7[0].baseaddress is set to '0' on reset.
>>
>> This use-case is applicable for any board/EVM which doesn't have
>> any peripheral connected to gpmc cs0, for example BeagleXM and
>> BeagleBone, so DT boot mode fails.
>>
>> This patch adds of_have_populated_dt() check before creating
>> device, so that for DT boot mode, gpmc probe will not be called
>> which is expected behavior, as gpmc is not supported yet from DT.
> 
> I'm applying this one into omap-for-v3.7-rc1/fixes-part2.
> 
> Next time, please also cc linux-omap@vger.kernel.org for series
> like this. I'm sure the people reading the omap list are interested
> in these.

This patch appears to be masking an underlying issue. How about 
something like the following ...

Cheers
Jon

>From 753a4928bf6f7baa4c001bdca3d15a85e999db4c Mon Sep 17 00:00:00 2001
From: Jon Hunter <jon-hunter@ti.com>
Date: Tue, 16 Oct 2012 15:22:58 -0500
Subject: [PATCH] ARM: OMAP2+: Allow kernel to boot even if GPMC fails to
 reserve memory

Currently, if the GPMC driver fails to reserve memory when probed we will
call BUG() and the kernel will not boot. Instead of calling BUG(), return
an error from probe and allow kernel to boot.

Tested on AM335x beagle bone board.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
---
 arch/arm/mach-omap2/gpmc.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c
index 5ac5cf3..8f0d3c8 100644
--- a/arch/arm/mach-omap2/gpmc.c
+++ b/arch/arm/mach-omap2/gpmc.c
@@ -868,9 +868,9 @@ static void __devexit gpmc_mem_exit(void)
 
 }
 
-static void __devinit gpmc_mem_init(void)
+static int __devinit gpmc_mem_init(void)
 {
-	int cs;
+	int cs, rc;
 	unsigned long boot_rom_space = 0;
 
 	/* never allocate the first page, to facilitate bug detection;
@@ -890,13 +890,17 @@ static void __devinit gpmc_mem_init(void)
 		if (!gpmc_cs_mem_enabled(cs))
 			continue;
 		gpmc_cs_get_memconf(cs, &base, &size);
-		if (gpmc_cs_insert_mem(cs, base, size) < 0)
-			BUG();
+		rc = gpmc_cs_insert_mem(cs, base, size);
+		if (IS_ERR_VALUE(rc))
+			return rc;
 	}
+
+	return 0;
 }
 
 static __devinit int gpmc_probe(struct platform_device *pdev)
 {
+	int rc;
 	u32 l;
 	struct resource *res;
 
@@ -936,7 +940,11 @@ static __devinit int gpmc_probe(struct platform_device *pdev)
 	dev_info(gpmc_dev, "GPMC revision %d.%d\n", GPMC_REVISION_MAJOR(l),
 		 GPMC_REVISION_MINOR(l));
 
-	gpmc_mem_init();
+	rc = gpmc_mem_init();
+	if (IS_ERR_VALUE(rc)) {
+		dev_err(gpmc_dev, "failed to reserve memory\n");
+		return rc;
+	}
 
 	if (IS_ERR_VALUE(gpmc_setup_irq()))
 		dev_warn(gpmc_dev, "gpmc_setup_irq failed\n");
-- 
1.7.9.5

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Tony Lindgren]

* Jon Hunter <jon-hunter@ti.com> [121016 14:00]:
> Hi Tony,
> 
> On 10/16/2012 12:48 PM, Tony Lindgren wrote:
> > * Richard Cochran <richardcochran@gmail.com> [121015 12:18]:
> >> From: hvaibhav@ti.com <hvaibhav@ti.com>
> >>
> >> With recent changes in omap gpmc driver code, in case of DT
> >> boot mode, where bootloader does not configure gpmc cs space
> >> will result into kernel BUG() inside gpmc_mem_init() function,
> >> as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
> >> gpmc_config7[0].baseaddress is set to '0' on reset.
> >>
> >> This use-case is applicable for any board/EVM which doesn't have
> >> any peripheral connected to gpmc cs0, for example BeagleXM and
> >> BeagleBone, so DT boot mode fails.
> >>
> >> This patch adds of_have_populated_dt() check before creating
> >> device, so that for DT boot mode, gpmc probe will not be called
> >> which is expected behavior, as gpmc is not supported yet from DT.
> > 
> > I'm applying this one into omap-for-v3.7-rc1/fixes-part2.
> > 
> > Next time, please also cc linux-omap@vger.kernel.org for series
> > like this. I'm sure the people reading the omap list are interested
> > in these.
> 
> This patch appears to be masking an underlying issue. How about 
> something like the following ...

OK that looks good to me. I'll drop the earlier fix and use
yours instead.

Regards,

Tony

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Jon Hunter]

On 10/16/2012 04:26 PM, Tony Lindgren wrote:
> * Jon Hunter <jon-hunter@ti.com> [121016 14:00]:
>> Hi Tony,
>>
>> On 10/16/2012 12:48 PM, Tony Lindgren wrote:
>>> * Richard Cochran <richardcochran@gmail.com> [121015 12:18]:
>>>> From: hvaibhav@ti.com <hvaibhav@ti.com>
>>>>
>>>> With recent changes in omap gpmc driver code, in case of DT
>>>> boot mode, where bootloader does not configure gpmc cs space
>>>> will result into kernel BUG() inside gpmc_mem_init() function,
>>>> as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
>>>> gpmc_config7[0].baseaddress is set to '0' on reset.
>>>>
>>>> This use-case is applicable for any board/EVM which doesn't have
>>>> any peripheral connected to gpmc cs0, for example BeagleXM and
>>>> BeagleBone, so DT boot mode fails.
>>>>
>>>> This patch adds of_have_populated_dt() check before creating
>>>> device, so that for DT boot mode, gpmc probe will not be called
>>>> which is expected behavior, as gpmc is not supported yet from DT.
>>>
>>> I'm applying this one into omap-for-v3.7-rc1/fixes-part2.
>>>
>>> Next time, please also cc linux-omap@vger.kernel.org for series
>>> like this. I'm sure the people reading the omap list are interested
>>> in these.
>>
>> This patch appears to be masking an underlying issue. How about 
>> something like the following ...
> 
> OK that looks good to me. I'll drop the earlier fix and use
> yours instead.

Hi Tony, sorry but I realised now that in my patch that I need to
take care of releasing and memory and clocks that were acquired 
during the probe. Here is a V2. If you prefer I can create a delta
patch also with the previous. 

Cheers
Jon

>From 91f5234d567c07ce1579b50e52de1a1e06ce5c68 Mon Sep 17 00:00:00 2001
From: Jon Hunter <jon-hunter@ti.com>
Date: Tue, 16 Oct 2012 15:22:58 -0500
Subject: [PATCH V2] ARM: OMAP2+: Allow kernel to boot even if GPMC fails to
 reserve memory

Currently, if the GPMC driver fails to reserve memory when probed we will
call BUG() and the kernel will not boot. Instead of calling BUG(), return
an error from probe and allow kernel to boot.

Boot tested on AM335x beagle bone board and OMAP4430 Panda board.

V2 changes:
- Ensure that clock and memory resources are released on error.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
---
 arch/arm/mach-omap2/gpmc.c |   24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-omap2/gpmc.c b/arch/arm/mach-omap2/gpmc.c
index 5ac5cf3..92b5718 100644
--- a/arch/arm/mach-omap2/gpmc.c
+++ b/arch/arm/mach-omap2/gpmc.c
@@ -868,9 +868,9 @@ static void __devexit gpmc_mem_exit(void)
 
 }
 
-static void __devinit gpmc_mem_init(void)
+static int __devinit gpmc_mem_init(void)
 {
-	int cs;
+	int cs, rc;
 	unsigned long boot_rom_space = 0;
 
 	/* never allocate the first page, to facilitate bug detection;
@@ -890,13 +890,21 @@ static void __devinit gpmc_mem_init(void)
 		if (!gpmc_cs_mem_enabled(cs))
 			continue;
 		gpmc_cs_get_memconf(cs, &base, &size);
-		if (gpmc_cs_insert_mem(cs, base, size) < 0)
-			BUG();
+		rc = gpmc_cs_insert_mem(cs, base, size);
+		if (IS_ERR_VALUE(rc)) {
+			while (--cs >= 0)
+				if (gpmc_cs_mem_enabled(cs))
+					gpmc_cs_delete_mem(cs);
+			return rc;
+		}
 	}
+
+	return 0;
 }
 
 static __devinit int gpmc_probe(struct platform_device *pdev)
 {
+	int rc;
 	u32 l;
 	struct resource *res;
 
@@ -936,7 +944,13 @@ static __devinit int gpmc_probe(struct platform_device *pdev)
 	dev_info(gpmc_dev, "GPMC revision %d.%d\n", GPMC_REVISION_MAJOR(l),
 		 GPMC_REVISION_MINOR(l));
 
-	gpmc_mem_init();
+	rc = gpmc_mem_init();
+	if (IS_ERR_VALUE(rc)) {
+		clk_disable_unprepare(gpmc_l3_clk);
+		clk_put(gpmc_l3_clk);
+		dev_err(gpmc_dev, "failed to reserve memory\n");
+		return rc;
+	}
 
 	if (IS_ERR_VALUE(gpmc_setup_irq()))
 		dev_warn(gpmc_dev, "gpmc_setup_irq failed\n");
-- 
1.7.9.5
 

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Tony Lindgren]

* Jon Hunter <jon-hunter@ti.com> [121017 07:43]:
> 
> On 10/16/2012 04:26 PM, Tony Lindgren wrote:
> > * Jon Hunter <jon-hunter@ti.com> [121016 14:00]:
> >> Hi Tony,
> >>
> >> On 10/16/2012 12:48 PM, Tony Lindgren wrote:
> >>> * Richard Cochran <richardcochran@gmail.com> [121015 12:18]:
> >>>> From: hvaibhav@ti.com <hvaibhav@ti.com>
> >>>>
> >>>> With recent changes in omap gpmc driver code, in case of DT
> >>>> boot mode, where bootloader does not configure gpmc cs space
> >>>> will result into kernel BUG() inside gpmc_mem_init() function,
> >>>> as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
> >>>> gpmc_config7[0].baseaddress is set to '0' on reset.
> >>>>
> >>>> This use-case is applicable for any board/EVM which doesn't have
> >>>> any peripheral connected to gpmc cs0, for example BeagleXM and
> >>>> BeagleBone, so DT boot mode fails.
> >>>>
> >>>> This patch adds of_have_populated_dt() check before creating
> >>>> device, so that for DT boot mode, gpmc probe will not be called
> >>>> which is expected behavior, as gpmc is not supported yet from DT.
> >>>
> >>> I'm applying this one into omap-for-v3.7-rc1/fixes-part2.
> >>>
> >>> Next time, please also cc linux-omap@vger.kernel.org for series
> >>> like this. I'm sure the people reading the omap list are interested
> >>> in these.
> >>
> >> This patch appears to be masking an underlying issue. How about 
> >> something like the following ...
> > 
> > OK that looks good to me. I'll drop the earlier fix and use
> > yours instead.
> 
> Hi Tony, sorry but I realised now that in my patch that I need to
> take care of releasing and memory and clocks that were acquired 
> during the probe. Here is a V2. If you prefer I can create a delta
> patch also with the previous. 

OK thanks I'll update it.

Regards,

Tony

RE: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Hiremath, Vaibhav]

On Wed, Oct 17, 2012 at 01:17:56, Hunter, Jon wrote:
> 
> On 10/15/2012 02:16 PM, Richard Cochran wrote:
> > From: hvaibhav@ti.com <hvaibhav@ti.com>
> > 
> > With recent changes in omap gpmc driver code, in case of DT
> > boot mode, where bootloader does not configure gpmc cs space
> > will result into kernel BUG() inside gpmc_mem_init() function,
> > as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
> > gpmc_config7[0].baseaddress is set to '0' on reset.
> 
> I am not sure I completely follow the logic here.
> 
> Won't this problem occur if the bootloader does not configure the gpmc
> cs space AND we are not using DT?
> 

That's what exactly the above comment describes.

> Is the csvalid bit set because we are booting from the internal ROM?
> 

As per TRM, the reset value of the CS0_valis bit is set to 0. I have pasted 
TRM statement below -

"Chip-select enable (reset value is 1 for CS[0] and 0 for CS[1-5])."

And same applies to OMAP3 family of devices.

> I guess I don't see why csvalid bit being set and a base-address of 0x0
> should not be allowed. That should be a valid combination.
> 

Yes, agreed.

> One problem I see with gpmc_mem_init() is that it assumes that
> BOOT_ROM_SPACE is 1MB for all devices starting at 0x0 apart from the
> apollon board. For newer devices such as OMAP4, there is only 48KB of
> internal ROM and only mapped to 0x0 when booting from internal ROM. So
> this needs to be fixed.
> 
> How much internal ROM does the AM335x have and where is it mapped?
> 

AM33xx memory map is something like,

Boot ROM  0x4000_0000 0x4001_FFFF 128KB
          0x4002_0000 0x4002_BFFF 48KB    32-bit Ex/R(1) - Public
Reserved  0x4002_C000 0x400F_FFFF 848KB   Reserved
Reserved  0x4010_0000 0x401F_FFFF 1MB     Reserved
Reserved  0x4020_0000 0x402E_FFFF 960KB   Reserved
Reserved  0x402f_0000 0x4020_03FF 64KB    Reserved
SRAM internal 0x402F_0400 0x402F_FFFF    32-bit Ex/R/W(1)


> > This use-case is applicable for any board/EVM which doesn't have
> > any peripheral connected to gpmc cs0, for example BeagleXM and
> > BeagleBone, so DT boot mode fails.
> > 
> > This patch adds of_have_populated_dt() check before creating
> > device, so that for DT boot mode, gpmc probe will not be called
> > which is expected behavior, as gpmc is not supported yet from DT.
> 
> Yes, but we do actually still allow some platform devices to be probed
> (such as dmtimers) when booting with DT that don't support DT yet. So
> this change prevents us from using the gpmc on boards when booting with DT.
> 

The idea here was,

In order to use GPMC in meaningful way, where some peripheral is connected 
to the GPMC, you must create platform_device for the probe to happen 
properly. Now all the devices I know so far, we have gpmc_smsc911x_init(), 
omap_nand_flash_init(), etc...
These api's are getting called only through machine_desc.init_xxx callbacks,
And in case of DT, we have centralized machine_desc definition for all 
platforms (board-generic.c). So even though you want to use GPMC for DT boot
mode, you can not make use of peripheral without changing board-files to 
change to create platform_device.

Does it make sense?

> I am not convinced that this is addressing the underlying problem with
> gpmc_mem_init().
> 

The patch you submitted is cleanup patch and is required irrespective of 
this patch. I believe this patch is just makes sure that, if you are booting 
from DT and you do not have meaningful DT node for GPMC and peripheral 
interfaced to it, no point in probing it. 

Does it make any sense???


On other hand, Your patch is anyway required, as that I would consider as 
cleanup of existing code (in error handling).

Thanks,
Vaibhav

> Cheers
> Jon
> 

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Jon Hunter]

On 10/18/2012 11:16 AM, Hiremath, Vaibhav wrote:
> On Wed, Oct 17, 2012 at 01:17:56, Hunter, Jon wrote:
>>
>> On 10/15/2012 02:16 PM, Richard Cochran wrote:
>>> From: hvaibhav@ti.com <hvaibhav@ti.com>
>>>
>>> With recent changes in omap gpmc driver code, in case of DT
>>> boot mode, where bootloader does not configure gpmc cs space
>>> will result into kernel BUG() inside gpmc_mem_init() function,
>>> as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
>>> gpmc_config7[0].baseaddress is set to '0' on reset.
>>
>> I am not sure I completely follow the logic here.
>>
>> Won't this problem occur if the bootloader does not configure the gpmc
>> cs space AND we are not using DT?
>>
> 
> That's what exactly the above comment describes.

Hmm ... you said "in the case of DT", but I am saying even "in the case
WITHOUT DT" this can happen. So I think the subject is mis-leading.

>> Is the csvalid bit set because we are booting from the internal ROM?
>>
> 
> As per TRM, the reset value of the CS0_valis bit is set to 0. I have pasted 
> TRM statement below -
> 
> "Chip-select enable (reset value is 1 for CS[0] and 0 for CS[1-5])."

The above two sentences don't see to agree ...

> And same applies to OMAP3 family of devices.

For which boot-modes? All or just the gpmc boot-modes?

My omap3430 beagle has been booting with DT fine for some time and I
have not encountered this problem even on the latest kernel with the
gpmc driver present.

>> I guess I don't see why csvalid bit being set and a base-address of 0x0
>> should not be allowed. That should be a valid combination.
>>
> 
> Yes, agreed.
> 
>> One problem I see with gpmc_mem_init() is that it assumes that
>> BOOT_ROM_SPACE is 1MB for all devices starting at 0x0 apart from the
>> apollon board. For newer devices such as OMAP4, there is only 48KB of
>> internal ROM and only mapped to 0x0 when booting from internal ROM. So
>> this needs to be fixed.
>>
>> How much internal ROM does the AM335x have and where is it mapped?
>>
> 
> AM33xx memory map is something like,
> 
> Boot ROM  0x4000_0000 0x4001_FFFF 128KB
>           0x4002_0000 0x4002_BFFF 48KB    32-bit Ex/R(1) - Public
> Reserved  0x4002_C000 0x400F_FFFF 848KB   Reserved
> Reserved  0x4010_0000 0x401F_FFFF 1MB     Reserved
> Reserved  0x4020_0000 0x402E_FFFF 960KB   Reserved
> Reserved  0x402f_0000 0x4020_03FF 64KB    Reserved
> SRAM internal 0x402F_0400 0x402F_FFFF    32-bit Ex/R/W(1)

Does the boot ROM get mapped to 0x0, when booting from ROM?

>>> This use-case is applicable for any board/EVM which doesn't have
>>> any peripheral connected to gpmc cs0, for example BeagleXM and
>>> BeagleBone, so DT boot mode fails.
>>>
>>> This patch adds of_have_populated_dt() check before creating
>>> device, so that for DT boot mode, gpmc probe will not be called
>>> which is expected behavior, as gpmc is not supported yet from DT.
>>
>> Yes, but we do actually still allow some platform devices to be probed
>> (such as dmtimers) when booting with DT that don't support DT yet. So
>> this change prevents us from using the gpmc on boards when booting with DT.
>>
> 
> The idea here was,
> 
> In order to use GPMC in meaningful way, where some peripheral is connected 
> to the GPMC, you must create platform_device for the probe to happen 
> properly. Now all the devices I know so far, we have gpmc_smsc911x_init(), 
> omap_nand_flash_init(), etc...
> These api's are getting called only through machine_desc.init_xxx callbacks,
> And in case of DT, we have centralized machine_desc definition for all 
> platforms (board-generic.c). So even though you want to use GPMC for DT boot
> mode, you can not make use of peripheral without changing board-files to 
> change to create platform_device.
> 
> Does it make sense?

Sure, if you are using one of the generic machine configurations for DT.
However, while this migration happens people may create their own custom
machine configurations for DT for testing things like smsc911x.

>> I am not convinced that this is addressing the underlying problem with
>> gpmc_mem_init().
>>
> 
> The patch you submitted is cleanup patch and is required irrespective of 
> this patch. I believe this patch is just makes sure that, if you are booting 
> from DT and you do not have meaningful DT node for GPMC and peripheral 
> interfaced to it, no point in probing it. 
> 
> Does it make any sense???

Yes, but do you also see the bug that is hiding in gpmc_mem_init()?

My point is to highlight this and not hide it, so that we can fix it
now. Otherwise if we wait until we enable the gpmc driver with DT and
this could hinder the DT migration later.

Jon

RE: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Hiremath, Vaibhav]

On Thu, Oct 18, 2012 at 22:12:07, Hunter, Jon wrote:
> 
> On 10/18/2012 11:16 AM, Hiremath, Vaibhav wrote:
> > On Wed, Oct 17, 2012 at 01:17:56, Hunter, Jon wrote:
> >>
> >> On 10/15/2012 02:16 PM, Richard Cochran wrote:
> >>> From: hvaibhav@ti.com <hvaibhav@ti.com>
> >>>
> >>> With recent changes in omap gpmc driver code, in case of DT
> >>> boot mode, where bootloader does not configure gpmc cs space
> >>> will result into kernel BUG() inside gpmc_mem_init() function,
> >>> as gpmc cs0 gpmc_config7[0].csvalid bit is set to '1' and
> >>> gpmc_config7[0].baseaddress is set to '0' on reset.
> >>
> >> I am not sure I completely follow the logic here.
> >>
> >> Won't this problem occur if the bootloader does not configure the gpmc
> >> cs space AND we are not using DT?
> >>
> > 
> > That's what exactly the above comment describes.
> 
> Hmm ... you said "in the case of DT", but I am saying even "in the case
> WITHOUT DT" this can happen. So I think the subject is mis-leading.
> 

Ok, may be my above statement was confusing. But the bottom line is,
We should GPMC without any pre-configuration (either at u-boot or ROM) will 
have this issue.


> >> Is the csvalid bit set because we are booting from the internal ROM?
> >>
> > 
> > As per TRM, the reset value of the CS0_valis bit is set to 0. I have pasted 
> > TRM statement below -
> > 
> > "Chip-select enable (reset value is 1 for CS[0] and 0 for CS[1-5])."
> 
> The above two sentences don't see to agree ...

Oops, it was typo mistake. I meant "is set to '1'"

> 
> > And same applies to OMAP3 family of devices.
> 
> For which boot-modes? All or just the gpmc boot-modes?
> 

That's reset value, and I believe it is applicable for all boot modes.

> My omap3430 beagle has been booting with DT fine for some time and I
> have not encountered this problem even on the latest kernel with the
> gpmc driver present.
> 

OMAp3430 beagle board has NAND flash available over GPMC-CS0 interface.

> >> I guess I don't see why csvalid bit being set and a base-address of 0x0
> >> should not be allowed. That should be a valid combination.
> >>
> > 
> > Yes, agreed.
> > 
> >> One problem I see with gpmc_mem_init() is that it assumes that
> >> BOOT_ROM_SPACE is 1MB for all devices starting at 0x0 apart from the
> >> apollon board. For newer devices such as OMAP4, there is only 48KB of
> >> internal ROM and only mapped to 0x0 when booting from internal ROM. So
> >> this needs to be fixed.
> >>
> >> How much internal ROM does the AM335x have and where is it mapped?
> >>
> > 
> > AM33xx memory map is something like,
> > 
> > Boot ROM  0x4000_0000 0x4001_FFFF 128KB
> >           0x4002_0000 0x4002_BFFF 48KB    32-bit Ex/R(1) - Public
> > Reserved  0x4002_C000 0x400F_FFFF 848KB   Reserved
> > Reserved  0x4010_0000 0x401F_FFFF 1MB     Reserved
> > Reserved  0x4020_0000 0x402E_FFFF 960KB   Reserved
> > Reserved  0x402f_0000 0x4020_03FF 64KB    Reserved
> > SRAM internal 0x402F_0400 0x402F_FFFF    32-bit Ex/R/W(1)
> 
> Does the boot ROM get mapped to 0x0, when booting from ROM?
> 

I expect, it should be same as OMAP4.

> >>> This use-case is applicable for any board/EVM which doesn't have
> >>> any peripheral connected to gpmc cs0, for example BeagleXM and
> >>> BeagleBone, so DT boot mode fails.
> >>>
> >>> This patch adds of_have_populated_dt() check before creating
> >>> device, so that for DT boot mode, gpmc probe will not be called
> >>> which is expected behavior, as gpmc is not supported yet from DT.
> >>
> >> Yes, but we do actually still allow some platform devices to be probed
> >> (such as dmtimers) when booting with DT that don't support DT yet. So
> >> this change prevents us from using the gpmc on boards when booting with DT.
> >>
> > 
> > The idea here was,
> > 
> > In order to use GPMC in meaningful way, where some peripheral is connected 
> > to the GPMC, you must create platform_device for the probe to happen 
> > properly. Now all the devices I know so far, we have gpmc_smsc911x_init(), 
> > omap_nand_flash_init(), etc...
> > These api's are getting called only through machine_desc.init_xxx callbacks,
> > And in case of DT, we have centralized machine_desc definition for all 
> > platforms (board-generic.c). So even though you want to use GPMC for DT boot
> > mode, you can not make use of peripheral without changing board-files to 
> > change to create platform_device.
> > 
> > Does it make sense?
> 
> Sure, if you are using one of the generic machine configurations for DT.
> However, while this migration happens people may create their own custom
> machine configurations for DT for testing things like smsc911x.
> 

If we want to think about all such use-cases, then yes, this patch is not 
required.

> >> I am not convinced that this is addressing the underlying problem with
> >> gpmc_mem_init().
> >>
> > 
> > The patch you submitted is cleanup patch and is required irrespective of 
> > this patch. I believe this patch is just makes sure that, if you are booting 
> > from DT and you do not have meaningful DT node for GPMC and peripheral 
> > interfaced to it, no point in probing it. 
> > 
> > Does it make any sense???
> 
> Yes, but do you also see the bug that is hiding in gpmc_mem_init()?
> 
> My point is to highlight this and not hide it, so that we can fix it
> now. Otherwise if we wait until we enable the gpmc driver with DT and
> this could hinder the DT migration later.
> 

As I already mentioned in my previous response, your patch is required 
irrespective of this patch. I would consider your patch as a cleanup patch.


Both the patches are independent, your patch is handling the error path 
properly, whereas, my patch makes sure that you don't unnecessarily probe 
GPMC if you are booting from DT and GPMC node is not present, as described 
above.


Thanks,
Vaibhav

> Jon
> 
> 

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Jon Hunter]

On 10/18/2012 01:04 PM, Hiremath, Vaibhav wrote:
> On Thu, Oct 18, 2012 at 22:12:07, Hunter, Jon wrote:

...

>> Yes, but do you also see the bug that is hiding in gpmc_mem_init()?
>>
>> My point is to highlight this and not hide it, so that we can fix it
>> now. Otherwise if we wait until we enable the gpmc driver with DT and
>> this could hinder the DT migration later.
>>
> 
> As I already mentioned in my previous response, your patch is required 
> irrespective of this patch. I would consider your patch as a cleanup patch.
> 
> 
> Both the patches are independent, your patch is handling the error path 
> properly, whereas, my patch makes sure that you don't unnecessarily probe 
> GPMC if you are booting from DT and GPMC node is not present, as described 
> above.

Your patch hides a bug. That's my point. How do you expect am335x ever
to support gpmc devices if this bug is not addressed?

So I think that you are over-simplifying it when you say that my patch
is just a clean-up patch. I agree that it is adding appropriate error
handling, but it also highlights the presence of a bug by allowing the
probe to fail.

Anyway, I don't care to debate this any further, we just need to fix
gpmc_mem_init().

Jon

RE: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Hiremath, Vaibhav]

On Fri, Oct 19, 2012 at 00:00:31, Hunter, Jon wrote:
> 
> On 10/18/2012 01:04 PM, Hiremath, Vaibhav wrote:
> > On Thu, Oct 18, 2012 at 22:12:07, Hunter, Jon wrote:
> 
> ...
> 
> >> Yes, but do you also see the bug that is hiding in gpmc_mem_init()?
> >>
> >> My point is to highlight this and not hide it, so that we can fix it
> >> now. Otherwise if we wait until we enable the gpmc driver with DT and
> >> this could hinder the DT migration later.
> >>
> > 
> > As I already mentioned in my previous response, your patch is required 
> > irrespective of this patch. I would consider your patch as a cleanup patch.
> > 
> > 
> > Both the patches are independent, your patch is handling the error path 
> > properly, whereas, my patch makes sure that you don't unnecessarily probe 
> > GPMC if you are booting from DT and GPMC node is not present, as described 
> > above.
> 
> Your patch hides a bug. That's my point. How do you expect am335x ever
> to support gpmc devices if this bug is not addressed?
> 

Jon,
May be my commit description was mis-leading to you.
I am not commenting anything on your bug-fix, but do not agree that it is 
anything to do with hiding a bug.

I only agree with you on one point, if someone wants to change the board-
file to use GPMC with DT boot mode, then he will not be able to use it.

> So I think that you are over-simplifying it when you say that my patch
> is just a clean-up patch. I agree that it is adding appropriate error
> handling, but it also highlights the presence of a bug by allowing the
> probe to fail.
> 
> Anyway, I don't care to debate this any further, 

Me neither...

> we just need to fix
> gpmc_mem_init().
> 

Agreed, and that's what your patch rightly doing it.

Thanks,
Vaibhav

> Jon
> 

Re: [PATCH 1/5] ARM: OMAP2+: gpmc: Fix kernel BUG for DT boot mode

[Jon Hunter]

On 10/18/2012 01:39 PM, Hiremath, Vaibhav wrote:
> On Fri, Oct 19, 2012 at 00:00:31, Hunter, Jon wrote:
>>
>> On 10/18/2012 01:04 PM, Hiremath, Vaibhav wrote:
>>> On Thu, Oct 18, 2012 at 22:12:07, Hunter, Jon wrote:
>>
>> ...
>>
>>>> Yes, but do you also see the bug that is hiding in gpmc_mem_init()?
>>>>
>>>> My point is to highlight this and not hide it, so that we can fix it
>>>> now. Otherwise if we wait until we enable the gpmc driver with DT and
>>>> this could hinder the DT migration later.
>>>>
>>>
>>> As I already mentioned in my previous response, your patch is required 
>>> irrespective of this patch. I would consider your patch as a cleanup patch.
>>>
>>>
>>> Both the patches are independent, your patch is handling the error path 
>>> properly, whereas, my patch makes sure that you don't unnecessarily probe 
>>> GPMC if you are booting from DT and GPMC node is not present, as described 
>>> above.
>>
>> Your patch hides a bug. That's my point. How do you expect am335x ever
>> to support gpmc devices if this bug is not addressed?
>>
> 
> Jon,
> May be my commit description was mis-leading to you.
> I am not commenting anything on your bug-fix, but do not agree that it is 
> anything to do with hiding a bug.

So we can agree is disagree on that ;-)

> I only agree with you on one point, if someone wants to change the board-
> file to use GPMC with DT boot mode, then he will not be able to use it.
> 
>> So I think that you are over-simplifying it when you say that my patch
>> is just a clean-up patch. I agree that it is adding appropriate error
>> handling, but it also highlights the presence of a bug by allowing the
>> probe to fail.
>>
>> Anyway, I don't care to debate this any further, 
> 
> Me neither...
> 
>> we just need to fix
>> gpmc_mem_init().
>>
> 
> Agreed, and that's what your patch rightly doing it.

No. My patch does not fix the _actual_ bug, it is still there. Why do
you think that the probe is still failing for am335x? Without fixing it
am335x will never be able to support gpmc. So gpmc_mem_init() still
needs to be fixed.

Jon