ks_dw_pcie_initiate_link_train() question

Hi Murali,

This code looks suspicious. Can you comment?

    void ks_dw_pcie_initiate_link_train(struct keystone_pcie *ks_pcie)
    {
        u32 val;

        /* Disable Link training */
        val = readl(ks_pcie->va_app_base + CMD_STATUS);
        val &= ~LTSSM_EN_VAL;
        writel(LTSSM_EN_VAL | val,  ks_pcie->va_app_base + CMD_STATUS);

Here we cleared the LTSSM_EN_VAL bit in "val", but then we add it right back in before writing it back to CMD_STATUS.

That looks like a cut and paste error to me, but of course I don't know the hardware.

        /* Initiate Link Training */
        val = readl(ks_pcie->va_app_base + CMD_STATUS);
        writel(LTSSM_EN_VAL | val,  ks_pcie->va_app_base + CMD_STATUS);
    }

Bjorn,

Good catch! That is a cut-n-paste error. Here is the description from device manual

================
Disable link training by de-asserting the LTSSM_EN bit in the PCIESS Command Status Register (CMD_STATUS[LTSSM_EN]=0). Upon reset, the LTSSM_EN is de-asserted automatically by hardware.

Initiate link training can be initiated by asserting LTSSM_EN bit in the CMD_STATUS register (CMD_STATUS[LTSSM_EN]=1).
================================================

Probably it works because it is de-asserted automatically upon reset by hardware. Let me test this and send you a patch?

Murali Karicheri
Linux Kernel, Keystone