Subject: [PATCH] pci: tegra: actually program REFCLK_CFG* on recent SoCs

From: [email-masked] (Stephen Warren)
Date: Thu, 30 Jun 2016 09:49:40 -0600

On 06/30/2016 07:47 AM, Thierry Reding wrote:
> On Fri, Jun 24, 2016 at 08:37:03AM -0600, Stephen Warren wrote:
>> From: Stephen Warren <[email-masked]>
>>
>> On recent SoCs, tegra_pcie_phy_enable() isn't called; but instead
>> tegra_pcie_enable_controller() calls tegra_xusb_phy_enable(). However,
>> part of tegra_pcie_phy_enable() needs to happen in all cases. Move that
>> code to tegra_pcie_port_enable() instead.
>>
>> For reference, NVIDIA's downstream Linux kernel performs this operation
>> in tegra_pcie_enable_rp_features(), which is called immediately after
>> tegra_pcie_port_enable(). Since that function doesn't exist in the mainline
>> driver, we'll just add it to the tail of tegra_pcie_port_enable() instead.
>>
>> Signed-off-by: Stephen Warren <[email-masked]>
>> ---
>>   drivers/pci/host/pci-tegra.c | 17 +++++++++--------
>>   1 file changed, 9 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
>> index 74887fedc3d4..2ec64a9e7943 100644
>> --- a/drivers/pci/host/pci-tegra.c
>> +++ b/drivers/pci/host/pci-tegra.c
>> @@ -541,12 +541,13 @@ static void tegra_pcie_port_reset(struct tegra_pcie_port *port)
>>
>>   static void tegra_pcie_port_enable(struct tegra_pcie_port *port)
>>   {
>> -	const struct tegra_pcie_soc_data *soc = port->pcie->soc_data;
>> +	struct tegra_pcie *pcie = port->pcie;
>> +	const struct tegra_pcie_soc_data *soc = pcie->soc_data;
>>   	unsigned long ctrl = tegra_pcie_port_get_pex_ctrl(port);
>>   	unsigned long value;
>>
>>   	/* enable reference clock */
>> -	value = afi_readl(port->pcie, ctrl);
>> +	value = afi_readl(pcie, ctrl);
>>   	value |= AFI_PEX_CTRL_REFCLK_EN;
>>
>>   	if (soc->has_pex_clkreq_en)
>> @@ -554,9 +555,14 @@ static void tegra_pcie_port_enable(struct tegra_pcie_port *port)
>>
>>   	value |= AFI_PEX_CTRL_OVERRIDE_EN;
>>
>> -	afi_writel(port->pcie, value, ctrl);
>> +	afi_writel(pcie, value, ctrl);
>>
>>   	tegra_pcie_port_reset(port);
>> +
>> +	/* Configure the reference clock driver */
>> +	pads_writel(pcie, soc->pads_refclk_cfg0, PADS_REFCLK_CFG0);
>> +	if (soc->num_ports > 2)
>> +		pads_writel(pcie, soc->pads_refclk_cfg1, PADS_REFCLK_CFG1);
>>   }
>
> This will actually write these two registers for each enabled port,
> which, while it shouldn't make a difference, is unnecessary. I've
> applied a slightly modified version of this patch. Specifically I moved
> this code to the tail of the tegra_pcie_phy_power_on() function, which
> is closest to where it was before.
>
> I've also applied the patch that changes the values that are written
> into this register, though I reversed the order because that made more
> sense to me. I've pushed both patches to the for-4.8/pci branch in the
> Tegra tree, can you please take a look if that still looks okay to you?

I think that will work. It's a pity the code location in the mainline 
kernel is going to diverge from the downstream kernel and U-Boot though.