From: Pali Rohár pali@kernel.org
Add comments to understand what this magic code is doing.
Signed-off-by: Pali Rohár pali@kernel.org Reviewed-by: Marek Behún marek.behun@nic.cz --- 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);