linux-kernel - Re: [PATCH v2] clk: Fix falling back to legacy parent string matching

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Message-ID: <45962393-0b88-46c3-500f-1eec29d1729c@codeaurora.org>
Date:   Fri, 16 Aug 2019 09:22:28 +0530
From:   Taniya Das <tdas@...eaurora.org>
To:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        Jerome Brunet <jbrunet@...libre.com>,
        Chen-Yu Tsai <wens@...e.org>
Subject: Re: [PATCH v2] clk: Fix falling back to legacy parent string matching

Hello Stephen,

Thanks for the patch, I have tested it on the device.

On 8/14/2019 3:11 AM, Stephen Boyd wrote:
> Calls to clk_core_get() will return ERR_PTR(-EINVAL) if we've started
> migrating a clk driver to use the DT based style of specifying parents
> but we haven't made any DT updates yet. This happens when we pass a
> non-NULL value as the 'name' argument of of_parse_clkspec(). That
> function returns -EINVAL in such a situation, instead of -ENOENT like we
> expected. The return value comes back up to clk_core_fill_parent_index()
> which proceeds to skip calling clk_core_lookup() because the error
> pointer isn't equal to -ENOENT, it's -EINVAL.
> 
> Furthermore, we blindly overwrite the error pointer returned by
> clk_core_get() with NULL when there isn't a legacy .name member
> specified in the parent map. This isn't too bad right now because we
> don't really care to differentiate NULL from an error, but in the future
> we should only try to do a legacy lookup if we know we might find
> something. This way DT lookups that fail don't try to lookup based on
> strings when there isn't any string to match, hiding the error from DT
> parsing.
> 
> Fix both these problems so that clk provider drivers can use the new
> style of parent mapping without having to also update their DT at the
> same time. This patch is based on an earlier patch from Taniya Das which
> checked for -EINVAL in addition to -ENOENT return values from
> clk_core_get().
> 
> Fixes: 601b6e93304a ("clk: Allow parents to be specified via clkspec index")
> Cc: Taniya Das <tdas@...eaurora.org>
> Cc: Jerome Brunet <jbrunet@...libre.com>
> Cc: Chen-Yu Tsai <wens@...e.org>
> Reported-by: Taniya Das <tdas@...eaurora.org>
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>
> ---
> 

Tested-by: Taniya Das <tdas@...eaurora.org>

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