On 24.09.21 22:59, Marek Behún wrote:
From: Pali Rohár <[email protected]>
Add comments to understand what this magic code is doing.
Signed-off-by: Pali Rohár <[email protected]>
Reviewed-by: Marek Behún <[email protected]>
Reviewed-by: Stefan Roese <[email protected]>
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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