Re: [PATCH] ARM: dts: dra7-evm: add parallel NOR flash support

[Roger Quadros <rogerq@ti.com>]

+Sourav for QSPI and Balaji for mmc

On 07/30/2014 10:40 PM, Pekon Gupta wrote:
> Hi Roger,
> 
> On Tue, Jul 29, 2014 at 5:45 PM, Roger Quadros <rogerq@ti.com> wrote:
>> On 07/23/2014 01:58 PM, Pekon Gupta wrote:
>>> This patch adds support for parallel NOR device (S29GL512S10) present on J6-EVM.
>>> The Flash device is connected to GPMC controller on chip-select[0] and accessed
>>> as memory-mapped device. It has data-witdh=x16, capacity-64MBytes(512Mbits) and
>>> is CFI compatible.
>>> As multiple devices are share GPMC pins on this board, so following board
>>> settings are required to detect NOR device:
>>>      SW5.1 (NAND_BOOTn) = OFF (logic-1)
>>>      SW5.2 (NOR_BOOTn)  = ON  (logic-0) /* Active-low */
>>>      SW5.3 (eMMC_BOOTn) = OFF (logic-1)
>>>      SW5.4 (QSPI_BOOTn) = OFF (logic-1)
>>
>> Why does NOR have any dependency on states of eMMC_BOOTn and QSPI_BOOTn?
>>
> If you see the schematics of J6-EVM, GPMC data and control lines are shared
> between NAND, NOR, eMMC (and probably QSPI also).
> I don't have access to TI's hardaware or board schematics anymore, so
> please double check.

I just took a deeper look in the schematics.
It has nothing to do with GPMC Data and control lines but with the address lines.
The GPMC address lines are muxed on the same pins of the SoC as QSPI and MMC2.
i.e. A13-A18,CS2 for QSPI and A19-A27,CS1 for MMC2

NAND can probably work simultaneously with QSPI and MMC2 but for NOR case, QSPI and MMC2
need to be disabled.

This is starting to look ugly where apart from changing the DIP switch the DTS has to be
hand modified to support a certain case.

Lets leave the most usable configuration for default case i.e. NAND, QSPI and MMC2 enabled and keep NOR information in the dts but keep it disabled with a note that if NOR is enabled then NAND, QSPI, and MMC2 nodes need to be disabled.

I will resend this patch with the relevant changes.

cheers,
-roger

> 
>>>
>>> Also to maintain NAND Boot functionality, following setting are kept as default
>>> - NAND status="enabled"
>>> - NOR status="disabled"
>>
>> Too bad they designed the hardware so that either NOR or NAND can be used at a time.
>> Better to mention about this limitation by stating that CS0 is shared between NOR and NAND
>> and only one can be used at a time.
>>
> NAND/NOR/eMMC/QSPI effectively all are storage devices, so users may
> not use all of
> them at once, so may be to optimize usage of pins they added multiple
> devices on CS0.
> Sorry, I may not be able to re-spin this patch anytime soon, as I have
> no access to TI
> resources so request you to please re-send it with appropriate commit
> log change as you wish.
> 
>>>
>>> Signed-off-by: Pekon Gupta <pekon@ti.com>
>>> ---
>>>
>>> /* Flash read/write access tested after enabling NOR sub-node in DT */
>>>    linux#> flash_erase /dev/mtd9 0 0
>>>    linux#> dd if=/dev/urandom of=/tmp/source.hex  bs=1c count=2048
>>>    linux#> mtd_debug write /dev/mtd9 0x0 2048 /tmp/source.hex
>>>    linux#> mtd_debug read  /dev/mtd9 0x0 2048 /tmp/destination.hex
>>>    linux#> diff /tmp/source.hex  /tmp/destination.hex
>>>
>>>
>>>  arch/arm/boot/dts/dra7-evm.dts | 141 ++++++++++++++++++++++++++++++++++++++++-
>>>  1 file changed, 140 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/arm/boot/dts/dra7-evm.dts b/arch/arm/boot/dts/dra7-evm.dts
>>> index 4adc280..1ee9727 100644
>>> --- a/arch/arm/boot/dts/dra7-evm.dts
>>> +++ b/arch/arm/boot/dts/dra7-evm.dts
>>> @@ -151,6 +151,66 @@
>>>                       0xd0    (PIN_OUTPUT | MUX_MODE0)        /* gpmc_be0n_cle */
>>>               >;
>>>       };
>>> +
>>> +     nor_flash_x16: nor_flash_x16 {
>>> +             /* On DRA7 EVM, NOR_BOOTn comes from DIP switch
>>> +              * So NOR flash requires following switch settings:
>>> +              * SW5.1 (NAND_BOOTn) = OFF (logic-1)
>>> +              * SW5.2 (NOR_BOOTn)  = ON  (logic-0) Active-low
>>> +              * SW5.3 (eMMC_BOOTn) = OFF (logic-1)
>>> +              * SW5.4 (QSPI_BOOTn) = OFF (logic-1)
>>> +              */
>>
>> The only requirement for NOR_BOOTn is SW5.2 = ON and SW5.1 (NAND_BOOTn) = OFF.
>>
> As mentioned above, please check board schematics
> IIRC, GPMC lines pass through various levels of on-board
> bi-directional multiplexers,
> And 'select' lines of these multiplexers are controlled indirectly via
> these xxx_BOOTn switches.
> 
> [...]
> 
>>>  &i2c1 {
>>> @@ -417,8 +477,9 @@
>>>       status = "okay";
>>>       pinctrl-names = "default";
>>>       pinctrl-0 = <&nand_flash_x16>;
>>> -     ranges = <0 0 0 0x01000000>;    /* minimum GPMC partition = 16MB */
>>> +     ranges = <0 0 0x08000000 0x04000000>;   /* address offset=128MB, range=512Mb=64MB */
>>>       nand@0,0 {
>>> +             status = "okay";
>>
>> Not needed. If it is not explicitly disabled it is always enabled by default.
>>
> Yes, but good to have clarity in DTS, as most users will just copy-paste TI-EVM
> DTS and then tweak it for their own custom board DTS. So better to have this
> mentioned explicitely.
> 
> 
> with regards, pekon
>