From: Damien Le Moal <Damien.LeMoal@wdc.com>
To: Anup Patel <anup@brainfault.org>
Cc: linux-riscv <linux-riscv@lists.infradead.org>,
Anup Patel <Anup.Patel@wdc.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>
Subject: Re: [PATCH 08/10] riscv: Add Kendryte K210 device tree
Date: Mon, 2 Mar 2020 05:08:42 +0000 [thread overview]
Message-ID: <BYAPR04MB58160D1A2B74D22332E498C1E7E70@BYAPR04MB5816.namprd04.prod.outlook.com> (raw)
In-Reply-To: CAAhSdy2eGOifb6Ov6hfy=-QsjvFCKgZqqX1tiq1Z=wFrLpz9CA@mail.gmail.com
On 2020/03/02 14:05, Anup Patel wrote:
> On Mon, Mar 2, 2020 at 10:21 AM Damien Le Moal <Damien.LeMoal@wdc.com> wrote:
>>
>> On 2020/03/02 13:22, Anup Patel wrote:
>>> On Mon, Mar 2, 2020 at 9:46 AM Damien Le Moal <Damien.LeMoal@wdc.com> wrote:
>>>>
>>>> On 2020/03/02 13:07, Anup Patel wrote:
>>>> [...]
>>>>>> + sram0: memory@80000000 {
>>>>>> + device_type = "memory";
>>>>>> + reg = <0x80000000 0x400000>;
>>>>>> + };
>>>>>> +
>>>>>> + sram1: memory@80400000 {
>>>>>> + device_type = "memory";
>>>>>> + reg = <0x80400000 0x200000>;
>>>>>> + };
>>>>>> +
>>>>>> + kpu_sram: memory@80600000 {
>>>>>> + device_type = "memory";
>>>>>> + reg = <0x80600000 0x200000>;
>>>>>> + };
>>>>>
>>>>> No need to have separate DT node for each RAM bank. This can be
>>>>> express as single DT node as follows:
>>>>>
>>>>> sram: memory@80000000 {
>>>>> device_type = "memory";
>>>>> reg = <0x80000000 0x400000>,
>>>>> <0x80400000 0x200000>,
>>>>> <0x80600000 0x200000>;
>>>>> };
>>>>
>>>> This is to match the U-boot device tree that Sean wrote. So I would rather keep
>>>> it like this. And strictly speaking, if one wants to add a driver for the KPU,
>>>> having the kpu memory segment for it separate makes it easy to reference it from
>>>> a kpu device entry. But granted, the two sram segments can be declared with a
>>>> single memory entry.
>>>
>>> But, that's not the preferred way of describing memory banks on the
>>> same machine.
>>> Usually, we create multiple memory DT nodes for NUMA systems.
>>>
>>> You can also refer various ARM/ARM64 DTS files.
>>
>> Oops... Sent an answer to this to the wrong email... Here it is again:
>>
>> Yes, I understand. But in the case of the K210, that last 2MB segment is really
>> special as by default it is not usable as regular SRAM. I think it may be better
>> to reflect that in the device tree. The K210 soc_early_init() call back can
>> probe for that special entry too to see if it has to be turned on for use as
>> regular memory or not (i.e. if a kpu driver will use it).
>>
>> Since booting Linux with 6MB of memory will be even more challenging than with
>> 8, I agree that we may never see the case of a kpu driver being used. But I
>> personally like making that special case clear in the device tree. No strong
>> objection to your simplification though. So if you really object, I will go with it.
>>
>
> I understand that it is helping you to distinguish last 2MB segment but this is
> also possible using with single memory DT node as follows:
>
> sram: memory@80000000 {
> device_type = "memory";
> reg = <0x80000000 0x400000>,
> <0x80400000 0x200000>,
> <0x80600000 0x200000>;
> reg-names = "sram0", "sram1", "kpu_sram";
> };
Nice trick. I did not know about it. Will use that then !
>
> The K210 soc_early_init() can do the following:
> 1. Find memory DT node having device_type = "memory"
> 2. Find bank number for "kpu_sram" based on "reg-names DT property
> 3. Get based address of KPU SRAM from "reg" property based on bank
> number found in step2 above.
>
> The reg-names is a standard DT property used to distinguish multiple
> memory regions of device. Same can be used to distinguish multiple
> banks of memory DT node.
>
> I am not adamant on having single memory DT node but just wanted
> to let you know that this is not a preferred way for non-NUMA system.
Understood. Will use your proposed syntax.
>
> Regards,
> Anup
>
--
Damien Le Moal
Western Digital Research
next prev parent reply other threads:[~2020-03-02 5:08 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-12 10:34 [PATCH 00/10] Kendryte k210 SoC boards support Damien Le Moal
2020-02-12 10:34 ` [PATCH 01/10] riscv: Fix gitignore Damien Le Moal
2020-02-20 0:15 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 02/10] riscv: Force flat memory model with no-mmu Damien Le Moal
2020-02-14 20:18 ` Sean Anderson
2020-02-15 2:15 ` Damien Le Moal
2020-02-15 2:26 ` Sean Anderson
2020-02-15 2:40 ` Damien Le Moal
2020-03-02 3:48 ` Anup Patel
2020-03-04 18:38 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 03/10] riscv: Unaligned load/store handling for M_MODE Damien Le Moal
2020-03-02 3:57 ` Anup Patel
2020-03-04 19:28 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 04/10] riscv: Add BUILTIN_DTB support Damien Le Moal
2020-03-02 3:58 ` Anup Patel
2020-03-04 19:28 ` Palmer Dabbelt
2020-03-05 4:58 ` Anup Patel
2020-03-05 5:14 ` Damien Le Moal
2020-03-05 5:37 ` Anup Patel
2020-03-05 6:13 ` Damien Le Moal
2020-03-08 6:10 ` Anup Patel
2020-03-05 8:18 ` Atish Patra
2020-03-07 0:02 ` Sean Anderson
2020-03-07 1:51 ` Atish Patra
2020-03-07 2:08 ` Sean Anderson
2020-03-06 23:56 ` Sean Anderson
2020-02-12 10:34 ` [PATCH 05/10] riscv: Add SOC early init support Damien Le Moal
2020-03-04 19:28 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 06/10] riscv: Add Kendryte K210 SoC support Damien Le Moal
2020-02-14 20:31 ` Sean Anderson
2020-03-04 19:38 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 07/10] riscv: Select required drivers for Kendryte SOC Damien Le Moal
2020-03-02 3:59 ` Anup Patel
2020-03-04 19:44 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 08/10] riscv: Add Kendryte K210 device tree Damien Le Moal
2020-02-14 20:51 ` Sean Anderson
2020-02-15 2:34 ` Damien Le Moal
2020-02-15 2:48 ` Sean Anderson
2020-02-15 3:00 ` Damien Le Moal
2020-02-18 14:12 ` Carlos Eduardo de Paula
2020-02-18 14:18 ` Sean Anderson
2020-02-18 14:30 ` Carlos Eduardo de Paula
2020-02-18 17:48 ` Sean Anderson
2020-02-18 19:26 ` Carlos Eduardo de Paula
2020-02-19 9:06 ` Wladimir J. van der Laan
2020-02-19 22:28 ` Sean Anderson
2020-02-20 10:48 ` Wladimir J. van der Laan
2020-02-22 19:07 ` Wladimir J. van der Laan
2020-04-01 17:55 ` Drew Fustini
2020-04-02 2:24 ` Damien Le Moal
2020-02-19 8:50 ` Wladimir J. van der Laan
2020-02-27 19:43 ` Sean Anderson
2020-03-02 4:06 ` Anup Patel
2020-03-02 4:15 ` Damien Le Moal
2020-03-02 4:22 ` Anup Patel
2020-03-02 4:51 ` Damien Le Moal
2020-03-02 5:05 ` Anup Patel
2020-03-02 5:08 ` Damien Le Moal [this message]
2020-03-07 0:18 ` Sean Anderson
2020-03-07 4:11 ` Anup Patel
2020-03-04 19:44 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 09/10] riscv: Kendryte K210 default config Damien Le Moal
2020-03-02 4:07 ` Anup Patel
2020-03-04 19:44 ` Palmer Dabbelt
2020-02-12 10:34 ` [PATCH 10/10] riscv: create a loader.bin for the kendryte kflash.py tool Damien Le Moal
2020-03-02 4:08 ` Anup Patel
2020-03-04 19:44 ` Palmer Dabbelt
2020-02-14 15:05 ` [PATCH 00/10] Kendryte k210 SoC boards support Carlos Eduardo de Paula
2020-02-15 2:02 ` Damien Le Moal
2020-02-17 13:28 ` Carlos Eduardo de Paula
2020-02-26 21:31 ` Carlos Eduardo de Paula
2020-02-27 2:18 ` Damien Le Moal
2020-02-28 20:32 ` Sean Anderson
2020-03-02 3:01 ` Damien Le Moal
2020-03-02 3:53 ` Sean Anderson
2020-03-02 4:11 ` Damien Le Moal
2020-03-02 4:18 ` Sean Anderson
2020-03-02 4:54 ` Damien Le Moal
2020-03-02 4:56 ` Sean Anderson
2020-03-02 5:03 ` Damien Le Moal
2020-03-02 4:17 ` Anup Patel
2020-03-02 4:21 ` Sean Anderson
2020-03-02 4:48 ` Damien Le Moal
2020-03-02 4:51 ` Damien Le Moal
2020-03-02 5:02 ` Sean Anderson
2020-03-02 5:11 ` Damien Le Moal
2020-03-02 5:25 ` Sean Anderson
2020-03-02 5:43 ` Damien Le Moal
2020-03-04 19:44 ` Palmer Dabbelt
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