linux-kernel - Re: [PATCH v6 4/4] soc: imx8m: change to use platform driver

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Date:   Tue, 24 Nov 2020 10:48:20 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Alice Guo <alice.guo@....com>
Cc:     robh+dt@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
        linux-imx@....com, peng.fan@....com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v6 4/4] soc: imx8m: change to use platform driver

On Tue, Nov 24, 2020 at 09:59:49AM +0800, Alice Guo wrote:
> Directly reading ocotp register depends on that bootloader enables ocotp
> clk, which is not always effective, so change to use nvmem API. Using
> nvmem API requires to support driver defer probe and thus change
> soc-imx8m.c to use platform driver.
> 
> The other reason is that directly reading ocotp register causes kexec
> kernel hang because the 1st kernel running will disable unused clks
> after kernel boots up, and then ocotp clk will be disabled even if
> bootloader enables it. When kexec kernel, ocotp clk needs to be enabled
> before reading ocotp registers, and nvmem API with platform driver
> supported can accomplish this.
> 
> Signed-off-by: Alice Guo <alice.guo@....com>

I already reviewed it. You skipped all my review tags from v5.

Reviewed-by: Krzysztof Kozlowski <krzk@...nel.org>

Best regards,
Krzysztof

> ---
> 
> v2: remove the subject prefix "LF-2571-4"
> v3: Keep the original way which uses device_initcall to read soc unique
>     ID, and add the other way which uses module_platform_driver and
>     nvmem API, so that it will not break the old version DTBs.
> v4: delete "__maybe_unused"
>     delete MODULE_DEVICE_TABLE(of, imx8m_soc_match);
>     rename match table, "fsl,imx8mm/n/q/p" is actually a machine
> compabile and "fsl,imx8mm/n/q/p-soc" is a compabile of soc@0
>     delete "flag" and change to determine whether the pointer is NULL
>     ues of_find_matching_node_and_match()
>     delete of_match_ptr()
> v5: add cleanup part "of_node_put"
>     add note to explain that why device_initcall still exists
> v6: none