Re: [PATCH u-boot-marvell 3/9] arm: mvebu: a38x: serdes: Add comments for hws_pex_config() code

On 24.09.21 22:59, Marek Behún wrote:

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

Reviewed-by: Stefan Roese sr@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