* Implementing NAND driver on a PrimeCell SMC PL350 series
@ 2013-01-11 5:49 Daniel Tang
2013-01-11 11:02 ` Ricard Wanderlof
0 siblings, 1 reply; 6+ messages in thread
From: Daniel Tang @ 2013-01-11 5:49 UTC (permalink / raw)
To: linux-mtd
Hi,
I'm trying to write a NAND driver for the PL350 memory controller.
The problem is that the memory controller abstracts quite a lot of the processes needed to access the NAND. For example, the controller handles all the hardware controlling (like dealing with the CLE and ALE lines). This makes it difficult to write a driver that integrates cleanly with the current NAND subsystem of the kernel.
The issue specifically is the cmd_ctrl function that my driver needs to provide. When the kernel needs to write a command and address, it calls the function multiple times to write all the information. E.g. set CLE, write command, set ALE, then write one byte of the page address at a time. The controller, on the other hand, needs all that information to be in a single write to the controller. It does this by embedding the command into the address and have the data value be the page address.
There is a flow chart on page 51 of the reference manual if this seems unclear (http://infocenter.arm.com/help/topic/com.arm.doc.ddi0380g/DDI0380G_smc_pl350_series_r2p1_trm.pdf).
Can anyone advise what would be the best way to implement the driver?
Thanks,
Daniel
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Implementing NAND driver on a PrimeCell SMC PL350 series
2013-01-11 5:49 Implementing NAND driver on a PrimeCell SMC PL350 series Daniel Tang
@ 2013-01-11 11:02 ` Ricard Wanderlof
2013-01-12 10:01 ` Daniel Tang
2013-01-14 17:57 ` Mike Dunn
0 siblings, 2 replies; 6+ messages in thread
From: Ricard Wanderlof @ 2013-01-11 11:02 UTC (permalink / raw)
To: Daniel Tang; +Cc: linux-mtd@lists.infradead.org
On Fri, 11 Jan 2013, Daniel Tang wrote:
> I'm trying to write a NAND driver for the PL350 memory controller.
>
> The problem is that the memory controller abstracts quite a lot of the
> processes needed to access the NAND. For example, the controller handles
> all the hardware controlling (like dealing with the CLE and ALE lines).
> This makes it difficult to write a driver that integrates cleanly with
> the current NAND subsystem of the kernel.
>
> The issue specifically is the cmd_ctrl function that my driver needs to
> provide. When the kernel needs to write a command and address, it calls
> the function multiple times to write all the information. E.g. set CLE,
> write command, set ALE, then write one byte of the page address at a
> time. The controller, on the other hand, needs all that information to
> be in a single write to the controller. It does this by embedding the
> command into the address and have the data value be the page address.
Have you looked among the existing NAND controller drivers in
drivers/mtd/nand to see if there's another driver which has similar
requirements which you could use as a starting point? It's not unusual for
NAND controllers to do some of the operations automatically, and the mtd
framework supports this by letting you replace higher-level functions with
functions from the driver, and not just the low-level functions such as
hwcontrol and read_byte.
/Ricard
--
Ricard Wolf Wanderlöf ricardw(at)axis.com
Axis Communications AB, Lund, Sweden www.axis.com
Phone +46 46 272 2016 Fax +46 46 13 61 30
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Implementing NAND driver on a PrimeCell SMC PL350 series
2013-01-11 11:02 ` Ricard Wanderlof
@ 2013-01-12 10:01 ` Daniel Tang
2013-01-12 11:19 ` Ricard Wanderlof
2013-01-14 17:57 ` Mike Dunn
1 sibling, 1 reply; 6+ messages in thread
From: Daniel Tang @ 2013-01-12 10:01 UTC (permalink / raw)
To: Ricard Wanderlof; +Cc: linux-mtd@lists.infradead.org
On 11/01/2013, at 10:02 PM, Ricard Wanderlof <ricard.wanderlof@axis.com> wrote:
>
> On Fri, 11 Jan 2013, Daniel Tang wrote:
>
>> I'm trying to write a NAND driver for the PL350 memory controller.
>>
>> The problem is that the memory controller abstracts quite a lot of the processes needed to access the NAND. For example, the controller handles all the hardware controlling (like dealing with the CLE and ALE lines). This makes it difficult to write a driver that integrates cleanly with the current NAND subsystem of the kernel.
>>
>> The issue specifically is the cmd_ctrl function that my driver needs to provide. When the kernel needs to write a command and address, it calls the function multiple times to write all the information. E.g. set CLE, write command, set ALE, then write one byte of the page address at a time. The controller, on the other hand, needs all that information to be in a single write to the controller. It does this by embedding the command into the address and have the data value be the page address.
>
> Have you looked among the existing NAND controller drivers in drivers/mtd/nand to see if there's another driver which has similar requirements which you could use as a starting point? It's not unusual for NAND controllers to do some of the operations automatically, and the mtd framework supports this by letting you replace higher-level functions with functions from the driver, and not just the low-level functions such as hwcontrol and read_byte.
>
> /Ricard
> --
> Ricard Wolf Wanderlöf ricardw(at)axis.com
> Axis Communications AB, Lund, Sweden www.axis.com
> Phone +46 46 272 2016 Fax +46 46 13 61 30
I didn't know high level functions could be overridden. Most of the drivers I looked through didn't override the 'nand_command' function for example, so I wasn't aware it was possible.
As per your advice, I also read through some of the other NAND drivers. Although they didn't have anything similar to what I need, I have a good idea of where to head.
Thanks,
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Implementing NAND driver on a PrimeCell SMC PL350 series
2013-01-12 10:01 ` Daniel Tang
@ 2013-01-12 11:19 ` Ricard Wanderlof
2013-01-13 12:57 ` alessandro.maro
0 siblings, 1 reply; 6+ messages in thread
From: Ricard Wanderlof @ 2013-01-12 11:19 UTC (permalink / raw)
To: Daniel Tang; +Cc: linux-mtd@lists.infradead.org
On Sat, 12 Jan 2013, Daniel Tang wrote:
> I didn't know high level functions could be overridden. Most of the
> drivers I looked through didn't override the 'nand_command' function for
> example, so I wasn't aware it was possible.
A long time ago, the functions in nand_base.c were marked with things like
"REPLACABLE" or somesuch to show that they could be replaced with
user-defined functions.
I guess you have to read through things like nand_scan_defaults() e.g.
/* check, if a user supplied command function given */
if (chip->cmdfunc == NULL)
chip->cmdfunc = nand_command;
etc to get an idea of what to replace.
Of course, if the existing driver framwork is not flexible enough for
your needs, patches are always welcome.
> As per your advice, I also read through some of the other NAND drivers.
> Although they didn't have anything similar to what I need, I have a good
> idea of where to head.
Ok, good!
/Ricard
--
Ricard Wolf Wanderlöf ricardw(at)axis.com
Axis Communications AB, Lund, Sweden www.axis.com
Phone +46 46 272 2016 Fax +46 46 13 61 30
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: Implementing NAND driver on a PrimeCell SMC PL350 series
2013-01-12 11:19 ` Ricard Wanderlof
@ 2013-01-13 12:57 ` alessandro.maro
0 siblings, 0 replies; 6+ messages in thread
From: alessandro.maro @ 2013-01-13 12:57 UTC (permalink / raw)
To: ricard.wanderlof; +Cc: dt.tangr, linux-mtd
Inviato da iPhone
Il giorno 12/gen/2013, alle ore 12:25, "Ricard Wanderlof" <ricard.wanderlof@axis.com> ha scritto:
>
> On Sat, 12 Jan 2013, Daniel Tang wrote:
>
>> I didn't know high level functions could be overridden. Most of the drivers I looked through didn't override the 'nand_command' function for example, so I wasn't aware it was possible.
>
> A long time ago, the functions in nand_base.c were marked with things like "REPLACABLE" or somesuch to show that they could be replaced with user-defined functions.
>
> I guess you have to read through things like nand_scan_defaults() e.g.
>
> /* check, if a user supplied command function given */
> if (chip->cmdfunc == NULL)
> chip->cmdfunc = nand_command;
>
> etc to get an idea of what to replace.
>
> Of course, if the existing driver framwork is not flexible enough for your needs, patches are always welcome.
>
>> As per your advice, I also read through some of the other NAND drivers. Although they didn't have anything similar to what I need, I have a good idea of where to head.
>
> Ok, good!
>
> /Ricard
> --
> Ricard Wolf Wanderlöf ricardw(at)axis.com
> Axis Communications AB, Lund, Sweden www.axis.com
> Phone +46 46 272 2016 Fax +46 46 13 61 30
>
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Implementing NAND driver on a PrimeCell SMC PL350 series
2013-01-11 11:02 ` Ricard Wanderlof
2013-01-12 10:01 ` Daniel Tang
@ 2013-01-14 17:57 ` Mike Dunn
1 sibling, 0 replies; 6+ messages in thread
From: Mike Dunn @ 2013-01-14 17:57 UTC (permalink / raw)
To: linux-mtd
On 01/11/2013 03:02 AM, Ricard Wanderlof wrote:
>
> On Fri, 11 Jan 2013, Daniel Tang wrote:
>
>> I'm trying to write a NAND driver for the PL350 memory controller.
>>
>> The problem is that the memory controller abstracts quite a lot of the
>> processes needed to access the NAND. For example, the controller handles all
>> the hardware controlling (like dealing with the CLE and ALE lines). This makes
>> it difficult to write a driver that integrates cleanly with the current NAND
>> subsystem of the kernel.
>>
>> The issue specifically is the cmd_ctrl function that my driver needs to
>> provide. When the kernel needs to write a command and address, it calls the
>> function multiple times to write all the information. E.g. set CLE, write
>> command, set ALE, then write one byte of the page address at a time. The
>> controller, on the other hand, needs all that information to be in a single
>> write to the controller. It does this by embedding the command into the
>> address and have the data value be the page address.
>
> Have you looked among the existing NAND controller drivers in drivers/mtd/nand
> to see if there's another driver which has similar requirements which you could
> use as a starting point? It's not unusual for NAND controllers to do some of the
> operations automatically, and the mtd framework supports this by letting you
> replace higher-level functions with functions from the driver, and not just the
> low-level functions such as hwcontrol and read_byte.
You might find it helpful to take a look at docg4.c in particular. This device
is a nand wrapped in a proprietary controller, which sounds similiar to your
hardware. This device does not have control of low-level lines either.
Hope this helps,
Mike
^ permalink raw reply [flat|nested] 6+ messages in thread
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2013-01-11 5:49 Implementing NAND driver on a PrimeCell SMC PL350 series Daniel Tang
2013-01-11 11:02 ` Ricard Wanderlof
2013-01-12 10:01 ` Daniel Tang
2013-01-12 11:19 ` Ricard Wanderlof
2013-01-13 12:57 ` alessandro.maro
2013-01-14 17:57 ` Mike Dunn
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