Re: [PATCH] pci: tegra: correctly program PADS_REFCLK registers

[Thierry Reding <thierry.reding@gmail.com>]

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On Wed, Jun 22, 2016 at 09:34:21AM -0600, Stephen Warren wrote:
> On 06/22/2016 06:57 AM, Thierry Reding wrote:
> > On Tue, Jun 21, 2016 at 12:46:40PM -0600, Stephen Warren wrote:
> > > From: Stephen Warren <swarren@nvidia.com>
> > > 
> > > The value that should be programmed into the PADS_REFCLK register varies
> > > per SoC. Fix the Tegra PCIe driver to program the correct values. Future
> > > SoCs will require different values in cfg0/1, so the two values are stored
> > > separately in the per-SoC data structures.
> > > 
> > > For reference, the values are all documented in NV bug 1771116 comment 20.
> > > Rhe ASIC team has validated all these values, except for the Tegra20 value
> > > which is simply left unchanged in this patch.
> 
> > > diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
> 
> > > @@ -2078,6 +2070,7 @@ static const struct tegra_pcie_soc_data tegra20_pcie_data = {
> > >   	.msi_base_shift = 0,
> > >   	.pads_pll_ctl = PADS_PLL_CTL_TEGRA20,
> > >   	.tx_ref_sel = PADS_PLL_CTL_TXCLKREF_DIV10,
> > > +	.pads_refclk_cfg0 = 0xfa5cfa5c,
> > >   	.has_pex_clkreq_en = false,
> > >   	.has_pex_bias_ctrl = false,
> > >   	.has_intr_prsnt_sense = false,
> > > @@ -2090,6 +2083,8 @@ static const struct tegra_pcie_soc_data tegra30_pcie_data = {
> > >   	.msi_base_shift = 8,
> > >   	.pads_pll_ctl = PADS_PLL_CTL_TEGRA30,
> > >   	.tx_ref_sel = PADS_PLL_CTL_TXCLKREF_BUF_EN,
> > > +	.pads_refclk_cfg0 = 0xfa5cfa5c,
> > > +	.pads_refclk_cfg1 = 0xfa5cfa5c,
> > >   	.has_pex_clkreq_en = true,
> > >   	.has_pex_bias_ctrl = true,
> > >   	.has_intr_prsnt_sense = true,
> > > @@ -2102,6 +2097,7 @@ static const struct tegra_pcie_soc_data tegra124_pcie_data = {
> > >   	.msi_base_shift = 8,
> > >   	.pads_pll_ctl = PADS_PLL_CTL_TEGRA30,
> > >   	.tx_ref_sel = PADS_PLL_CTL_TXCLKREF_BUF_EN,
> > > +	.pads_refclk_cfg0 = 0x44ac44ac,
> > >   	.has_pex_clkreq_en = true,
> > >   	.has_pex_bias_ctrl = true,
> > >   	.has_intr_prsnt_sense = true,
> > 
> > I think it'd be nice to have these decoded into their individual fields,
> > to reduce the magic. We already define the register fields, so it seems
> > sensible to use them.
> 
> I did consider that. However, the specification from the ASIC team is always
> the raw values. Decoding them into bitfields is only going to make it harder
> to verify whether the correct values are present (since the reader has to
> manually expand the math), and introduce the possibility of errors during
> the expansion process. I think using raw numbers is better in this case.

Alright, fine with me:

Acked-by: Thierry Reding <treding@nvidia.com>

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