On 24.09.21 22:59, Marek Behún wrote:
> From: Pali Rohár <pali at kernel.org>
>
> Add comments to understand what this magic code is doing.
>
> Signed-off-by: Pali Rohár <pali at kernel.org>
> Reviewed-by: Marek Behún <marek.behun at nic.cz>
Reviewed-by: Stefan Roese <sr at denx.de>
Thanks,
Stefan
> ---
> arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c b/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c
> index 717bcfb29c..0eb31d589c 100644
> --- a/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c
> +++ b/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c
> @@ -42,6 +42,7 @@ int hws_pex_config(const struct serdes_map *serdes_map, u8 count)
> continue;
> }
>
> + /* Set Device/Port Type to RootComplex */
> pex_idx = serdes_type - PEX0;
> tmp = reg_read(PEX_CAPABILITIES_REG(pex_idx));
> tmp &= ~(0xf << 20);
> @@ -122,12 +123,18 @@ int hws_pex_config(const struct serdes_map *serdes_map, u8 count)
> }
>
> next_busno++;
> +
> + /*
> + * Read maximum link speed. It must be 0x2 (5.0 GT/s) as this
> + * value was set in serdes_power_up_ctrl() function.
> + */
> temp_pex_reg = reg_read((PEX_CFG_DIRECT_ACCESS
> (pex_idx, PEX_LINK_CAPABILITY_REG)));
> temp_pex_reg &= 0xf;
> if (temp_pex_reg != 0x2)
> continue;
>
> + /* Read negotiated link speed */
> temp_reg = (reg_read(PEX_CFG_DIRECT_ACCESS(
> pex_idx,
> PEX_LINK_CTRL_STAT_REG)) &
> @@ -155,6 +162,7 @@ int hws_pex_config(const struct serdes_map *serdes_map, u8 count)
> continue;
> }
>
> + /* Find start of the PCI Express Capability registers */
> while ((pex_config_read(pex_idx, first_busno, 0, 0, addr)
> & 0xff) != 0x10) {
> addr = (pex_config_read(pex_idx, first_busno, 0,
> @@ -173,11 +181,15 @@ int hws_pex_config(const struct serdes_map *serdes_map, u8 count)
> tmp = reg_read(PEX_LINK_CTRL_STATUS2_REG(pex_idx));
> DEBUG_RD_REG(PEX_LINK_CTRL_STATUS2_REG(pex_idx), tmp);
> tmp &= ~(BIT(0) | BIT(1));
> - tmp |= BIT(1);
> + tmp |= BIT(1); /* Force Target Link Speed to 5.0 GT/s */
> tmp |= BIT(6); /* Select Deemphasize (-3.5d_b) */
> reg_write(PEX_LINK_CTRL_STATUS2_REG(pex_idx), tmp);
> DEBUG_WR_REG(PEX_LINK_CTRL_STATUS2_REG(pex_idx), tmp);
>
> + /*
> + * Enable Auto Speed change. When set, link will issue link
> + * speed change to max possible link speed.
> + */
> tmp = reg_read(PEX_CTRL_REG(pex_idx));
> DEBUG_RD_REG(PEX_CTRL_REG(pex_idx), tmp);
> tmp |= BIT(10);
>
Viele Grüße,
Stefan
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