[PATCH v4 58/80] drm/omap: pll: fix iteration loop check

[Laurent Pinchart]

Hi Tomi,

Thank you for the patch.

On Tue, Nov 24, 2020 at 02:45:16PM +0200, Tomi Valkeinen wrote:
> If the PLL calc function is given bad parameters, n_start/m_start may be
> higher than n_stop/m_stop, which leads to the loops iterating through
> the whole u32 number space.
> 
> Fix this by failing early on such cases.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> ---
>  drivers/gpu/drm/omapdrm/dss/pll.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/omapdrm/dss/pll.c b/drivers/gpu/drm/omapdrm/dss/pll.c
> index 1212f3cc52d1..12926218c436 100644
> --- a/drivers/gpu/drm/omapdrm/dss/pll.c
> +++ b/drivers/gpu/drm/omapdrm/dss/pll.c
> @@ -222,6 +222,9 @@ bool dss_pll_calc_a(const struct dss_pll *pll, unsigned long clkin,
>  	n_stop = min((unsigned)(clkin / fint_hw_min), hw->n_max);
>  	n_inc = 1;
>  
> +	if (n_start > n_stop)
> +		return false;
> +
>  	if (hw->errata_i886) {
>  		swap(n_start, n_stop);
>  		n_inc = -1;
> @@ -239,6 +242,9 @@ bool dss_pll_calc_a(const struct dss_pll *pll, unsigned long clkin,
>  				hw->m_max);
>  		m_inc = 1;
>  
> +		if (m_start > m_stop)
> +			continue;
> +
>  		if (hw->errata_i886) {
>  			swap(m_start, m_stop);
>  			m_inc = -1;

-- 
Regards,

Laurent Pinchart