linux-kernel - Re: [V2] [PATCH] clk: zynqmp: pll: add set_pll_mode to check condition in zynqmp_pll

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Date:   Thu, 1 Apr 2021 10:02:02 +0800
From:   "quanyang.wang" <quanyang.wang@...driver.com>
To:     Stephen Boyd <sboyd@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Michael Turquette <mturquette@...libre.com>,
        Michal Simek <michal.simek@...inx.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rajan Vaja <rajan.vaja@...inx.com>,
        Jolly Shah <jolly.shah@...inx.com>, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [V2] [PATCH] clk: zynqmp: pll: add set_pll_mode to check
 condition in zynqmp_pll_enable

Hi Stephen,

On 4/1/21 9:49 AM, Stephen Boyd wrote:
> Quoting quanyang.wang@...driver.com (2021-03-30 05:17:01)
>> From: Quanyang Wang <quanyang.wang@...driver.com>
>>
>> If there is a IOCTL_SET_PLL_FRAC_MODE request sent to ATF ever,
>> we shouldn't skip invoking PM_CLOCK_ENABLE fn even though this
>> pll has been enabled. In ATF implementation, it will only assign
>> the mode to the variable (struct pm_pll *)pll->mode when handling
>> IOCTL_SET_PLL_FRAC_MODE call. Invoking PM_CLOCK_ENABLE can force
>> ATF send request to PWU to set the pll mode to PLL's register.
>>
>> There is a scenario that happens in enabling VPLL_INT(clk_id:96):
>> 1) VPLL_INT has been enabled during booting.
>> 2) A driver calls clk_set_rate and according to the rate, the VPLL_INT
>>     should be set to FRAC mode. Then zynqmp_pll_set_mode is called
>>     to pass IOCTL_SET_PLL_FRAC_MODE to ATF. Note that at this point
>>     ATF just stores the mode to a variable.
>> 3) This driver calls clk_prepare_enable and zynqmp_pll_enable is
>>     called to try to enable VPLL_INT pll. Because of 1), the function
>>     zynqmp_pll_enable just returns without doing anything after checking
>>     that this pll has been enabled.
>>
>> In the scenario above, the pll mode of VPLL_INT will never be set
>> successfully. So adding set_pll_mode to check condition to fix it.
>>
>> Signed-off-by: Quanyang Wang <quanyang.wang@...driver.com>
>> Tested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>> ---
> Any Fixes tag?

Will add it at V3 patch.

Thanks,

Quanyang