Re: [Qemu-devel] [PATCH v4 3/3] i.MX: Add an i.MX25 specific CCM class/instance.

[Peter Crosthwaite]

On Fri, Nov 27, 2015 at 11:54 AM, Jean-Christophe DUBOIS
<address@hidden> wrote:
> Le 27/11/2015 03:39, Peter Crosthwaite a écrit :
>
> On Wed, Nov 25, 2015 at 11:16 PM, Jean-Christophe Dubois
> <address@hidden> wrote:
>
> Signed-off-by: Jean-Christophe Dubois <address@hidden>
>
> This seems to slow down boot performance for i.MX25 Linux. Admittedly,
> the issue looks to be in timeout code for an unmodelled periph (NAND):
>
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1 at
> /home/pcrost/poky/build/tmp/work-shared/qemuarmv5imx/kernel-source/drivers/mtd/nand/mxc_nand.c:464
> wait_op_done+0xf0/0x114()
> timeout! useirq=0
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper Not tainted 4.2.1 #1
> Hardware name: Freescale i.MX25 (Device Tree Support)
> [<c000eec8>] (unwind_backtrace) from [<c000d2b0>] (show_stack+0x10/0x14)
> [<c000d2b0>] (show_stack) from [<c0019154>] (warn_slowpath_common+0x74/0xac)
> [<c0019154>] (warn_slowpath_common) from [<c00191bc>]
> (warn_slowpath_fmt+0x30/0x40)
> [<c00191bc>] (warn_slowpath_fmt) from [<c036eaa0>] (wait_op_done+0xf0/0x114)
> [<c036eaa0>] (wait_op_done) from [<c0369698>] (nand_scan_ident+0xdc/0x1560)
> [<c0369698>] (nand_scan_ident) from [<c036e6a8>] (mxcnd_probe+0x378/0x5c0)
> [<c036e6a8>] (mxcnd_probe) from [<c03081a4>] (platform_drv_probe+0x44/0xac)
> [<c03081a4>] (platform_drv_probe) from [<c0306654>]
> (driver_probe_device+0x180/0x2c4)
> [<c0306654>] (driver_probe_device) from [<c0306824>]
> (__driver_attach+0x8c/0x90)
> [<c0306824>] (__driver_attach) from [<c0304a80>]
> (bus_for_each_dev+0x70/0xa0)
> [<c0304a80>] (bus_for_each_dev) from [<c0305d08>]
> (bus_add_driver+0x188/0x210)
> [<c0305d08>] (bus_add_driver) from [<c03071d4>] (driver_register+0x78/0xf8)
> [<c03071d4>] (driver_register) from [<c00095e0>]
> (do_one_initcall+0x84/0x1f0)
> [<c00095e0>] (do_one_initcall) from [<c071bd24>]
> (kernel_init_freeable+0x108/0x1c8)
> [<c071bd24>] (kernel_init_freeable) from [<c0541a0c>] (kernel_init+0x8/0xec)
> [<c0541a0c>] (kernel_init) from [<c000a340>] (ret_from_fork+0x14/0x34)
> ---[ end trace 13248cb1a1bbcb9c ]---
>
> <<Delay happens here>>
>
> nand: No NAND device found
> ...
>
> Without this patch, the delay is around 2 seconds, with this patch it
> is 10+. Any idea what would cause it? Are you removing the NAND from
> DTS for your testing and do we not care about these errors paths?
>
> Regards,
> Peter
>
> The kernel I am testing with is 3.19.0 but without without DTS tree.
> Linux version 3.19.0 (address@hidden) (gcc version 4.6.3 (GCC) ) #2 Mon Jun
> 22 00:32:04 CEST 2015
>
> So I am not up to date on this side and I might not test the same devices as
> you do as I generated a "minimal" kernel for my test.
>

So the DTB+defconfig boot is actually in pretty good shape. That NAND
thing is the only real bootlog issue. All other missing peripherals
fail gracefully.

> Anyway, testing the timer code I found that running "sleep 60" on both PTF
> doesn't give the expected 60 seconds in "real world time":
>
> On i.MX31 (using i.MX31 CCM) => 47 seconds

> On i.MX25 (using i.MX31 CCM) => 52 seconds (before change. close enough?)

Confirmed this result, exactly the same here.

> On i.MX25 (using i.MX25 CCM) => 80 seconds
>
> Another indication, the bogomips:
>
> On i.MX31 (using i.MX31 CCM) => 78
> On i.MX25 (using i.MX31 CCM) => 87 (before change. close enough?)
> On i.MX25 (using i.MX25 CCM) => 133
>

I wouldn't worry about this, this is rarely accurate in QEMU.

Regards,
Peter

> So, yes, for some reason "time goes slower" after switching to i.MX25 CCM
> ... (but it was also going too fast before with i.MX31 CCM)
>
> As the CCM doesn't really provide any clock (just a clock value) something
> must not be right in the way the i.MX GPT timer is computing time.
>
> I need to look after this.
>
> JC
>
> ---
>
> Changes since v1:
>  * rework loging to match other i.MX drivers
>
> Changes since v2:
>  * We moved to an inheritance QOM scheme
>
> Changes since v3:
>  * Rework logging based on comments.
>
>  hw/arm/fsl-imx25.c          |   2 +-
>  hw/misc/Makefile.objs       |   1 +
>  hw/misc/imx25_ccm.c         | 276
> ++++++++++++++++++++++++++++++++++++++++++++
>  include/hw/arm/fsl-imx25.h  |   4 +-
>  include/hw/misc/imx25_ccm.h |  59 ++++++++++
>  5 files changed, 339 insertions(+), 3 deletions(-)
>  create mode 100644 hw/misc/imx25_ccm.c
>  create mode 100644 include/hw/misc/imx25_ccm.h
>
>