Re: [PATCH v2 2/4] drm/msm/dsi/phy: Protect PHY_CMN_CLK_CFG1 against clock driver

[Dmitry Baryshkov]

On Mon, Feb 03, 2025 at 06:29:19PM +0100, Krzysztof Kozlowski wrote:
> PHY_CMN_CLK_CFG1 register is updated by the PHY driver and by a mux
> clock from Common Clock Framework:
> devm_clk_hw_register_mux_parent_hws().  There could be a path leading to
> concurrent and conflicting updates between PHY driver and clock
> framework, e.g. changing the mux and enabling PLL clocks.
> 
> Add dedicated spinlock to be sure all PHY_CMN_CLK_CFG1 updates are
> synchronized.
> 
> Fixes: 1ef7c99d145c ("drm/msm/dsi: add support for 7nm DSI PHY/PLL")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> 
> ---
> 
> Changes in v2:
> 1. Store BIT(4) and BIT(5) in local var in dsi_pll_enable_global_clk()
> ---
>  drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 35 +++++++++++++++++++------------
>  1 file changed, 22 insertions(+), 13 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 c164f845653816291ad96c863257f75462ef58e7..e26f53f7cde8f0f6419a633f5d39784dc2e5bb98 100644
> --- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
> +++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
> @@ -83,6 +83,9 @@ struct dsi_pll_7nm {
>  	/* protects REG_DSI_7nm_PHY_CMN_CLK_CFG0 register */
>  	spinlock_t postdiv_lock;
>  
> +	/* protects REG_DSI_7nm_PHY_CMN_CLK_CFG1 register */
> +	spinlock_t pclk_mux_lock;
> +
>  	struct pll_7nm_cached_state cached_state;
>  
>  	struct dsi_pll_7nm *slave;
> @@ -381,22 +384,32 @@ static void dsi_pll_cmn_clk_cfg0_write(struct dsi_pll_7nm *pll, u32 val)
>  	spin_unlock_irqrestore(&pll->postdiv_lock, flags);
>  }
>  
> -static void dsi_pll_disable_global_clk(struct dsi_pll_7nm *pll)
> +static void dsi_pll_cmn_clk_cfg1_update(struct dsi_pll_7nm *pll, u32 mask,
> +					u32 val)
>  {
> +	unsigned long flags;
>  	u32 data;
>  
> +	spin_lock_irqsave(&pll->pclk_mux_lock, flags);
>  	data = readl(pll->phy->base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
> -	writel(data & ~BIT(5), pll->phy->base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
> +	data &= ~mask;
> +	data |= val & mask;
> +
> +	writel(data, pll->phy->base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
> +	spin_unlock_irqrestore(&pll->pclk_mux_lock, flags);
> +}
> +
> +static void dsi_pll_disable_global_clk(struct dsi_pll_7nm *pll)
> +{
> +	dsi_pll_cmn_clk_cfg1_update(pll, BIT(5), 0);
>  }
>  
>  static void dsi_pll_enable_global_clk(struct dsi_pll_7nm *pll)
>  {
> -	u32 data;
> +	u32 cfg_1 = BIT(5) | BIT(4);

Please define these two bits too.

>  
>  	writel(0x04, pll->phy->base + REG_DSI_7nm_PHY_CMN_CTRL_3);
> -
> -	data = readl(pll->phy->base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
> -	writel(data | BIT(5) | BIT(4), pll->phy->base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
> +	dsi_pll_cmn_clk_cfg1_update(pll, cfg_1, cfg_1);
>  }
>  
>  static void dsi_pll_phy_dig_reset(struct dsi_pll_7nm *pll)
> @@ -574,7 +587,6 @@ static int dsi_7nm_pll_restore_state(struct msm_dsi_phy *phy)
>  {
>  	struct dsi_pll_7nm *pll_7nm = to_pll_7nm(phy->vco_hw);
>  	struct pll_7nm_cached_state *cached = &pll_7nm->cached_state;
> -	void __iomem *phy_base = pll_7nm->phy->base;
>  	u32 val;
>  	int ret;
>  
> @@ -585,11 +597,7 @@ static int dsi_7nm_pll_restore_state(struct msm_dsi_phy *phy)
>  
>  	dsi_pll_cmn_clk_cfg0_write(pll_7nm,
>  				   cached->bit_clk_div | (cached->pix_clk_div << 4));
> -
> -	val = readl(phy_base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
> -	val &= ~0x3;
> -	val |= cached->pll_mux;
> -	writel(val, phy_base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
> +	dsi_pll_cmn_clk_cfg1_update(pll_7nm, 0x3, cached->pll_mux);
>  
>  	ret = dsi_pll_7nm_vco_set_rate(phy->vco_hw,
>  			pll_7nm->vco_current_rate,
> @@ -742,7 +750,7 @@ static int pll_7nm_register(struct dsi_pll_7nm *pll_7nm, struct clk_hw **provide
>  					pll_by_2_bit,
>  				}), 2, 0, pll_7nm->phy->base +
>  					REG_DSI_7nm_PHY_CMN_CLK_CFG1,
> -				0, 1, 0, NULL);
> +				0, 1, 0, &pll_7nm->pclk_mux_lock);
>  		if (IS_ERR(hw)) {
>  			ret = PTR_ERR(hw);
>  			goto fail;
> @@ -787,6 +795,7 @@ static int dsi_pll_7nm_init(struct msm_dsi_phy *phy)
>  	pll_7nm_list[phy->id] = pll_7nm;
>  
>  	spin_lock_init(&pll_7nm->postdiv_lock);
> +	spin_lock_init(&pll_7nm->pclk_mux_lock);
>  
>  	pll_7nm->phy = phy;
>  
> 
> -- 
> 2.43.0
> 

-- 
With best wishes
Dmitry