[PATCH 02/11] omap2/3: Fix DEBUG_LL for omap zoom2/3

[Pandita, Vikram]

>-----Original Message-----
>From: linux-omap-owner at vger.kernel.org [mailto:linux-omap-
>owner at vger.kernel.org] On Behalf Of Pandita, Vikram
>Sent: Friday, April 30, 2010 4:37 PM
>To: Kevin Hilman; Tony Lindgren
>Cc: linux-arm-kernel at lists.infradead.org; linux-omap at vger.kernel.org; Pais,
>Allen
>Subject: RE: [PATCH 02/11] omap2/3: Fix DEBUG_LL for omap zoom2/3
>
>
>
>>-----Original Message-----
>>From: Kevin Hilman [mailto:khilman at deeprootsystems.com]
>>Sent: Friday, April 30, 2010 4:21 PM
>>To: Tony Lindgren
>>Cc: linux-arm-kernel at lists.infradead.org; Pandita, Vikram; linux-
>>omap at vger.kernel.org; Pais, Allen
>>Subject: Re: [PATCH 02/11] omap2/3: Fix DEBUG_LL for omap zoom2/3
>>
>>Tony Lindgren <tony at atomide.com> writes:
>>
>>> * Kevin Hilman <khilman at deeprootsystems.com> [100430 13:50]:
>>>> Tony Lindgren <tony at atomide.com> writes:
>>>>
>>>> > Zoom2 and 3 have UARTs only on the external debug board.
>>>> > GPMC needs to be mapped early to use it for DEBUG_LL.
>>>> >
>>>> > Additionally, 0xfb000000 overlaps with other areas, so
>>>> > use 0xfa400000 for the virtual address instead.
>>>> >
>>>> > Note that with the pending serial.c patches you need to
>>>> > set console=ttyS0,115200n8 as it will be the only UART
>>>> > mapped. To use DEBUG_LL, you need to pass also earlyprintk
>>>> > in cmdline.
>>>> >
>>>> > Cc: Allen Pais <allen.pais at ti.com>
>>>> > Cc: Vikram Pandita <vikram.pandita at ti.com>
>>>> > Signed-off-by: Tony Lindgren <tony at atomide.com>
>>>> > ---
>>>> >  arch/arm/kernel/head.S                         |   10 ++++++++++
>>>> >  arch/arm/mach-omap2/board-zoom-debugboard.c    |    2 +-
>>>> >  arch/arm/mach-omap2/include/mach/debug-macro.S |    4 ++--
>>>> >  arch/arm/mach-omap2/io.c                       |    9 +++++++++
>>>> >  arch/arm/plat-omap/include/plat/serial.h       |    2 +-
>>>> >  5 files changed, 23 insertions(+), 4 deletions(-)
>>>> >
>>>> > diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S
>>>> > index eb62bf9..fd870e1 100644
>>>> > --- a/arch/arm/kernel/head.S
>>>> > +++ b/arch/arm/kernel/head.S
>>>> > @@ -328,6 +328,16 @@ __create_page_tables:
>>>> >  	add	r0, r4, #0xd8000000 >> 18
>>>> >  	str	r3, [r0]
>>>> >  #endif
>>>> > +#if defined(CONFIG_MACH_OMAP_ZOOM2) ||
>>defined(CONFIG_MACH_OMAP_ZOOM3)
>>>> > +	/*
>>>> > +	 * Zoom2 and Zoom3 have UARTs only on the debug board.
>>>> > +	 * The debug board is connected to the GPMC.
>>>> > +	 */
>>>> > +	add	r0, r4, #0xfa000000 >> 18
>>>> > +	orr	r0, r0, #0x00400000 >> 18	@ ZOOM_UART_VIRT
>>>> > +	orr	r3, r7, #0x10000000		@ ZOOM_UART_BASE
>>>> > +	str	r3, [r0]
>>>> > +#endif
>>>>
>>>> I don't see why this part is needed.  The same mapping is done using
>>>> the .io_pg_offset in the machine description which is done just before
>>>> this in head.S
>>>
>>> That mapping does not cover the GPMC area where this UART is.
>>
>>Hmm, then shouldn't that be fixed?  I understood the .phys_io and and
>>.io_pg_offset fields of the mach_desc to be specifically for mapping
>>the early UART, and nothing else.
>
>Here is the problem -
>with current approach we need two mappings to happen and the
>MACHINE_START() code allows for only one via .io_pg_offset and .phys_io
>
>Why:
>Tony's approach is to pass the information about the debug uart number from
>the UART1 Scratchpad register.
>
>this introduces a dependency that
>UART1 registers also be mapped (virt<->phy).
>
>So for Tony's approach to work, .phys_io/.io_pg_offset continued to have
>0x4800000 based mapping and for external uart zoom3 port, create this extra
>mapping.
>
>So find a better way from compressed.S to pass the uart number to kernel,
>and we can solve the problem.

Reference to that dependency: 
Commit: 0c8219f0
<snip/start>
+/*
+ * Store the DEBUG_LL uart number into UART1 scratchpad register.
+ * See also debug-macro.S, and serial.c for related code.
+ *
+ * Please note that we currently assume that:
+ * - UART1 clocks are enabled for register access
+ * - UART1 scratchpad register can be used
+ */
+static void set_uart1_scratchpad(unsigned char port)
<snip/end>

>
>>
>>Kevin
>>
>
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