linux-kernel - Re: [PATCH v2 1/4] drm/msm/dsi/phy: Protect PHY_CMN_CLK

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Message-ID: <ef6b4d5c-df4c-478f-8544-7dacd90b88bf@quicinc.com>
Date: Mon, 10 Feb 2025 16:26:06 -0800
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Rob Clark
	<robdclark@...il.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean
 Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David
 Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] drm/msm/dsi/phy: Protect PHY_CMN_CLK_CFG0 updated
 from driver side



On 2/3/2025 9:29 AM, Krzysztof Kozlowski wrote:
> PHY_CMN_CLK_CFG0 register is updated by the PHY driver and by two
> divider clocks from Common Clock Framework:
> devm_clk_hw_register_divider_parent_hw().  Concurrent access by the
> clocks side is protected with spinlock, however driver's side in
> restoring state is not.  Restoring state is called from
> msm_dsi_phy_enable(), so there could be a path leading to concurrent and
> conflicting updates with clock framework.
> 
> Add missing lock usage on the PHY driver side, encapsulated in its own
> function so the code will be still readable.
> 
> Fixes: 1ef7c99d145c ("drm/msm/dsi: add support for 7nm DSI PHY/PLL")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> ---
>   drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
> index 031446c87daec0af3f81df324158311f5a80014e..c164f845653816291ad96c863257f75462ef58e7 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
> @@ -372,6 +372,15 @@ static void dsi_pll_enable_pll_bias(struct dsi_pll_7nm *pll)
>   	ndelay(250);
>   }
>   

Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>