[PATCH 5/6] PCI: imx6: Force Gen1 operation

[Pratyush Anand]

On Wed, Oct 16, 2013 at 12:06:39AM +0800, Marek Vasut wrote:
> Without forcing the PCIe core into Gen1 operation, the PCIe switch
> attached directly to the PCIe port is not recognised at all. The
> PCIe switch is Gen2 capable to make this issue even more puzzling.
> 
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Bjorn Helgaas <bhelgaas at google.com>
> Cc: Frank Li <lznuaa at gmail.com>
> Cc: Jingoo Han <jg1.han at samsung.com>
> Cc: Mohit KUMAR <Mohit.KUMAR at st.com>
> Cc: Pratyush Anand <pratyush.anand at st.com>
> Cc: Richard Zhu <r65037 at freescale.com>
> Cc: Sascha Hauer <s.hauer at pengutronix.de>
> Cc: Sean Cross <xobs at kosagi.com>
> Cc: Shawn Guo <shawn.guo at linaro.org>
> Cc: Siva Reddy Kallam <siva.kallam at samsung.com>
> Cc: Srikanth T Shivanand <ts.srikanth at samsung.com>
> Cc: Tim Harvey <tharvey at gateworks.com>
> Cc: Troy Kisky <troy.kisky at boundarydevices.com>
> Cc: Yinghai Lu <yinghai at kernel.org>
> ---
>  drivers/pci/host/pci-imx6.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/host/pci-imx6.c b/drivers/pci/host/pci-imx6.c
> index ca8c5de..8402e9a 100644
> --- a/drivers/pci/host/pci-imx6.c
> +++ b/drivers/pci/host/pci-imx6.c
> @@ -321,6 +321,7 @@ static void imx6_pcie_host_init(struct pcie_port *pp)
>  {
>  	int count = 0;
>  	struct imx6_pcie *imx6_pcie = to_imx6_pcie(pp);
> +	uint32_t tmp;
>  
>  	imx6_pcie_assert_core_reset(pp);
>  
> @@ -330,13 +331,23 @@ static void imx6_pcie_host_init(struct pcie_port *pp)
>  
>  	dw_pcie_setup_rc(pp);
>  
> +	/*
> +	 * FIXME:
> +	 * Force Gen1 operation. In case the IP block is in Gen2 operation
> +	 * mode, it does not detect the PCIe switch at all.
> +	 */
> +	tmp = readl(pp->dbi_base + 0x7c);
> +	tmp &= ~0xf;
> +	tmp |= 0x1;
> +	writel(tmp, pp->dbi_base + 0x7c);
> +

Since you are forcing RC to work in GEN1, so you will not be able to
connect any device at GEN2 now.

Yes, There are some buggy PCIe devices which works with GEN1 only host.

So better solution should be to initialize RC by default at GEN2 or
highest speed. Further, a parameter say gen_only can be passed from
DT to force GEN1 only mode.

What do you say?

Regards
Pratyush

>  	regmap_update_bits(imx6_pcie->iomuxc_gpr, IOMUXC_GPR12,
>  			IMX6Q_GPR12_PCIE_CTL_2, 1 << 10);
>  
>  	while (!dw_pcie_link_up(pp)) {
>  		usleep_range(100, 1000);
>  		count++;
> -		if (count >= 10) {
> +		if (count >= 200) {
>  			dev_err(pp->dev, "phy link never came up\n");
>  			dev_dbg(pp->dev,
>  				"DEBUG_R0: 0x%08x, DEBUG_R1: 0x%08x\n",
> -- 
> 1.8.4.rc3