linux-kernel - Re: [PATCH v2] clk: zynqmp: fix compile testing without ZYNQMP

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Date:   Mon, 21 Jun 2021 15:54:44 +0200
From:   Michal Simek <michal.simek@...inx.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Michal Simek <michal.simek@...inx.com>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Michal Simek <monstr@...str.eu>, git <git@...inx.com>,
        Michael Turquette <mturquette@...libre.com>,
        Punit Agrawal <punit1.agrawal@...hiba.co.jp>,
        Quanyang Wang <quanyang.wang@...driver.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v2] clk: zynqmp: fix compile testing without
 ZYNQMP_FIRMWARE



On 6/21/21 3:51 PM, Arnd Bergmann wrote:
> On Mon, Jun 21, 2021 at 3:14 PM Michal Simek <michal.simek@...inx.com> wrote:
>>
>> From: Arnd Bergmann <arnd@...db.de>
>>
>> When the firmware code is disabled, the incomplete error handling
>> in the clk driver causes compile-time warnings:
>>
>> drivers/clk/zynqmp/pll.c: In function 'zynqmp_pll_recalc_rate':
>> drivers/clk/zynqmp/pll.c:147:29: error: 'fbdiv' is used uninitialized [-Werror=uninitialized]
>>   147 |         rate =  parent_rate * fbdiv;
>>       |                 ~~~~~~~~~~~~^~~~~~~
>> In function 'zynqmp_pll_get_mode',
>>     inlined from 'zynqmp_pll_recalc_rate' at drivers/clk/zynqmp/pll.c:148:6:
>> drivers/clk/zynqmp/pll.c:61:27: error: 'ret_payload' is used uninitialized [-Werror=uninitialized]
>>    61 |         return ret_payload[1];
>>       |                ~~~~~~~~~~~^~~
>> drivers/clk/zynqmp/pll.c: In function 'zynqmp_pll_recalc_rate':
>> drivers/clk/zynqmp/pll.c:53:13: note: 'ret_payload' declared here
>>    53 |         u32 ret_payload[PAYLOAD_ARG_CNT];
>>       |             ^~~~~~~~~~~
>> drivers/clk/zynqmp/clk-mux-zynqmp.c: In function 'zynqmp_clk_mux_get_parent':
>> drivers/clk/zynqmp/clk-mux-zynqmp.c:57:16: error: 'val' is used uninitialized [-Werror=uninitialized]
>>    57 |         return val;
>>       |                ^~~
>>
>> As it was apparently intentional to support this for compile testing
>> purposes, change the code to have just enough error handling for the
>> compiler to not notice the remaining bugs.
>>
>> Fixes: 21f237534661 ("clk: zynqmp: Drop dependency on ARCH_ZYNQMP")
>> Signed-off-by: Arnd Bergmann <arnd@...db.de>
>> Signed-off-by: Michal Simek <michal.simek@...inx.com>
>> ---
>>
>> Changes in v2:
>> Based on discussion here
>> Link: https://lore.kernel.org/r/20210421134844.3297838-1-arnd@kernel.org
>> I have updated error return value which I got from clock core based on
>> error cases.
>>
>> zynqmp_clk_mux_get_parent() should return num_parents() as error defined in
>> clk_core_get_parent_by_index() where num_parents is incorrect index.
>>
>> Extend zynqmp_pll_get_mode() with PLL_MODE_ERROR to handle error case.
>>
>> zynqmp_pll_recalc_rate() returns 0 because __clk_core_init() consider 0 as
>> default rate. But maybe -1ul which was used by Arnd is also good option.
> 
> Looks good to me. You changed more than I did now, so it might be better
> to change my authorship to Co-developed-by, probably not worth respinning
> for that.

Let's see what Stephen said about these changes.

Thanks,
Michal