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| author | Pali Rohár <pali@kernel.org> | 2021-09-24 22:59:16 +0200 |
|---|---|---|
| committer | Stefan Roese <sr@denx.de> | 2021-10-08 08:33:52 +0200 |
| commit | 2d5f51f680be9461f87f0c99b55c68ad68633078 (patch) | |
| tree | 3447fd8cc33e2f7b3ad17918d356eedc967d11dd /arch | |
| parent | eb5d31645e1160345389d68b263d72112f5b9c46 (diff) | |
| download | u-boot-2d5f51f680be9461f87f0c99b55c68ad68633078.zip u-boot-2d5f51f680be9461f87f0c99b55c68ad68633078.tar.gz u-boot-2d5f51f680be9461f87f0c99b55c68ad68633078.tar.bz2 | |
arm: mvebu: a38x: serdes: Add comments for hws_pex_config() code
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>
Reviewed-by: Stefan Roese <sr@denx.de>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c b/arch/arm/mach-mvebu/serdes/a38x/ctrl_pex.c index 717bcfb..0eb31d5 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); |