linux-kernel - RE: [PATCH] clk: imx: imx8qxp-lpcg: use devm_platform_ioremap

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Date:   Thu, 5 Dec 2019 09:03:26 +0000
From:   Peng Fan <peng.fan@....com>
To:     Leonard Crestez <leonard.crestez@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Aisheng Dong <aisheng.dong@....com>,
        "sboyd@...nel.org" <sboyd@...nel.org>
CC:     "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        Abel Vesa <abel.vesa@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        dl-linux-imx <linux-imx@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alice Guo <alice.guo@....com>
Subject: RE: [PATCH] clk: imx: imx8qxp-lpcg: use
 devm_platform_ioremap_resource

> Subject: Re: [PATCH] clk: imx: imx8qxp-lpcg: use
> devm_platform_ioremap_resource
> 
> On 2019-12-05 3:38 AM, Peng Fan wrote:
> >> Subject: Re: [PATCH] clk: imx: imx8qxp-lpcg: use
> >> devm_platform_ioremap_resource
> >>
> >> On 2019-12-04 12:14 PM, Peng Fan wrote:
> >>> From: Peng Fan <peng.fan@....com>
> >>>
> >>> devm_platform_ioremap_resource() wraps platform_get_resource() and
> >>> devm_ioremap_resource(), we could use this API to simplify the code.
> >>>
> >>> Signed-off-by: Peng Fan <peng.fan@....com>
> >>
> >> This patch has been posted before and it breaks uart on imx8qxp-mek
> >> and possibly other things.
> >>
> >> The old and new paths are not equivalent:
> >> devm_platform_ioremap_resource calls devm_ioremap_resource differs
> >> from devm_ioremap by also calling devm_request_mem_region.
> >>
> >> This prevents other mappings in the area; this is not an issue for
> >> most drivers but imx8qxp-lpcg maps whole subsystems. For example:
> >>
> >>                   adma_lpcg: clock-controller@...00000 {
> >>                           compatible = "fsl,imx8qxp-lpcg-adma";
> >>                           reg = <0x59000000 0x2000000>;
> >>                           #clock-cells = <1>;
> >>                   };
> >>
> >>                   adma_lpuart0: serial@...60000 {
> >>                           reg = <0x5a060000 0x1000>;
> >> 			...
> >> 		};
> >>
> >> Previously: https://patchwork.kernel.org/patch/10908807/
> >
> > Thanks. I think at least need to provide some comments in code.
> 
> Yes, comments would help. I think it's actually the 3rd time this incorrect
> cleanup was posted.
> 
> But mapping entire subsystems (32mb at a time) for LPCG is deeply
> flawed: the LPCG areas are each 64k and they're interspersed among the
> peripherals. The correct solution is to have many small clock providers.
> 
> This is done by a series of patches from Aisheng, I think this is the latest one:
> 
> https://patchwork.kernel.org/patch/11248235/
> 
> If some aspects of that series are dubious perhaps they could be discussed
> and maybe the series could be split into smaller chunks?

That would be lots of lpcg nodes in device tree.

> 
> That series does brings many essential improvements to imx8 clk support.

Seems that pending for long time? What is the blocking point?

Regards,
Peng.

> 
> --
> Regards,
> Leonard