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From: Anup Patel <anup@brainfault.org>
To: Damien Le Moal <Damien.LeMoal@wdc.com>
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 10:35:32 +0530
Message-ID: <CAAhSdy2eGOifb6Ov6hfy=-QsjvFCKgZqqX1tiq1Z=wFrLpz9CA@mail.gmail.com> (raw)
In-Reply-To: <BYAPR04MB5816A2497FA764FB145D350FE7E70@BYAPR04MB5816.namprd04.prod.outlook.com>

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";
};

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.

Regards,
Anup


  reply index

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 [this message]
2020-03-02  5:08             ` Damien Le Moal
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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