Re: [PATCH v4 2/8] phy: rockchip: samsung-hdptx: Prevent divide-by-zero when computing clk rate

[Andy Yan <andy.yan@rock-chips.com>]

Hello,


On 6/12/26 07:45, Cristian Ciocaltea wrote:
> Calculating 'sdm' fraction in rk_hdptx_phy_clk_calc_rate_from_pll_cfg()
> could trigger a divide-by-zero, as it uses div_u64() with a denominator
> read directly from hardware: the values ropll_hw.sdm_deno,
> ropll_hw.sdc_deno, ropll_hw.sdc_n, and ropll_hw.sdc_num are populated
> from PLL registers which, in theory, could be left by the bootloader
> uninitialized/misconfigured.
> 
> Provide the necessary sanitization to avoid trusting the hardware state.
> 
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Closes: https://sashiko.dev/#/patchset/20260611-hdptx-clk-fixes-v3-0-67b1b0c00e16@collabora.com?part=1
> Fixes: 3481fc04d969 ("phy: rockchip: samsung-hdptx: Compute clk rate from PLL config")
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>

    Reviewed-by: Andy Yan <andy.yan@rock-chips.com>

> ---
>   drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c | 11 ++++++++---
>   1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
> index 710603afff86..8c044381b83a 100644
> --- a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
> +++ b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
> @@ -2270,10 +2270,15 @@ static u64 rk_hdptx_phy_clk_calc_rate_from_pll_cfg(struct rk_hdptx_phy *hdptx)
>   
>   	fout = PLL_REF_CLK * ropll_hw.pms_mdiv;
>   	if (ropll_hw.sdm_en) {
> +		val = 16U * ropll_hw.sdm_deno *
> +		      (ropll_hw.sdc_deno * ropll_hw.sdc_n - ropll_hw.sdc_num);
> +		if (!val) {
> +			dev_dbg(hdptx->dev, "%s invalid ROPLL hw state\n", __func__);
> +			return 0;
> +		}
> +
>   		sdm = div_u64(PLL_REF_CLK * ropll_hw.sdc_deno *
> -			      ropll_hw.pms_mdiv * ropll_hw.sdm_num,
> -			      16 * ropll_hw.sdm_deno *
> -			      (ropll_hw.sdc_deno * ropll_hw.sdc_n - ropll_hw.sdc_num));
> +			      ropll_hw.pms_mdiv * ropll_hw.sdm_num, val);
>   
>   		if (ropll_hw.sdm_num_sign)
>   			fout = fout - sdm;
>