Re: [PATCH 3/3] PCI: mediatek-gen3: Move reset/assert callbacks in .power_up()

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Nov 07, 2024 at 02:50:55PM +0100, Lorenzo Bianconi wrote:
> In order to make the code more readable, move phy and mac reset lines
> assert/de-assert configuration in .power_up callback
> (mtk_pcie_en7581_power_up/mtk_pcie_power_up).
> 
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  drivers/pci/controller/pcie-mediatek-gen3.c | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-mediatek-gen3.c b/drivers/pci/controller/pcie-mediatek-gen3.c
> index 8c8c733a145634cdbfefd339f4a692f25a6e24de..c0127d0fb4f059b9f9e816360130e183e8f0e990 100644
> --- a/drivers/pci/controller/pcie-mediatek-gen3.c
> +++ b/drivers/pci/controller/pcie-mediatek-gen3.c
> @@ -867,6 +867,13 @@ static int mtk_pcie_en7581_power_up(struct mtk_gen3_pcie *pcie)
>  	int err;
>  	u32 val;
>  
> +	/*
> +	 * The controller may have been left out of reset by the bootloader
> +	 * so make sure that we get a clean start by asserting resets here.
> +	 */
> +	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets,
> +				  pcie->phy_resets);
> +	reset_control_assert(pcie->mac_reset);

Add blank line here.

>  	/*
>  	 * Wait for the time needed to complete the bulk assert in
>  	 * mtk_pcie_setup for EN7581 SoC.
> @@ -941,6 +948,15 @@ static int mtk_pcie_power_up(struct mtk_gen3_pcie *pcie)
>  	struct device *dev = pcie->dev;
>  	int err;
>  
> +	/*
> +	 * The controller may have been left out of reset by the bootloader
> +	 * so make sure that we get a clean start by asserting resets here.
> +	 */
> +	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets,
> +				  pcie->phy_resets);
> +	reset_control_assert(pcie->mac_reset);
> +	usleep_range(10, 20);

Unrelated to this patch, but since you're moving it, do you know what
this delay is for?  Can we add a #define and a spec citation for it?

Is there a requirement that the PHY and MAC reset ordering be
different for EN7581 vs other chips?

EN7581:

  assert PHY reset
  assert MAC reset
  power on PHY
  deassert PHY reset
  deassert MAC reset

others:

  assert PHY reset
  assert MAC reset
  deassert PHY reset
  power on PHY
  deassert MAC reset

Is there one order that would work for both?

>  	/* PHY power on and enable pipe clock */
>  	err = reset_control_bulk_deassert(pcie->soc->phy_resets.num_resets, pcie->phy_resets);
>  	if (err) {
> @@ -1013,14 +1029,6 @@ static int mtk_pcie_setup(struct mtk_gen3_pcie *pcie)
>  	 * counter since the bulk is shared.
>  	 */
>  	reset_control_bulk_deassert(pcie->soc->phy_resets.num_resets, pcie->phy_resets);
> -	/*
> -	 * The controller may have been left out of reset by the bootloader
> -	 * so make sure that we get a clean start by asserting resets here.
> -	 */
> -	reset_control_bulk_assert(pcie->soc->phy_resets.num_resets, pcie->phy_resets);
> -
> -	reset_control_assert(pcie->mac_reset);
> -	usleep_range(10, 20);
>  
>  	/* Don't touch the hardware registers before power up */
>  	err = pcie->soc->power_up(pcie);
> 
> -- 
> 2.47.0
>