Re: [PATCH v6 3/4] PCI: qcom: Add equalization settings for 16.0 GT/s

[Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>]

On Wed, Sep 04, 2024 at 11:39:09AM +0200, Johan Hovold wrote:
> On Wed, Sep 04, 2024 at 12:41:59PM +0530, Manivannan Sadhasivam via B4 Relay wrote:
> > From: Shashank Babu Chinta Venkata <quic_schintav@quicinc.com>
> > 
> > During high data transmission rates such as 16.0 GT/s, there is an
> > increased risk of signal loss due to poor channel quality and interference.
> > This can impact receiver's ability to capture signals accurately. Hence,
> > signal compensation is achieved through appropriate lane equalization
> > settings at both transmitter and receiver. This will result in increased
> > PCIe signal strength.
> > 
> > Signed-off-by: Shashank Babu Chinta Venkata <quic_schintav@quicinc.com>
> > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
> > [mani: dropped the code refactoring and minor changes]
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

[...]

> > diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h
> > new file mode 100644
> > index 000000000000..259e04b7bdf9
> > --- /dev/null
> > +++ b/drivers/pci/controller/dwc/pcie-qcom-common.h
> > @@ -0,0 +1,8 @@
> > +/* SPDX-License-Identifier: GPL-2.0 */
> > +/*
> > + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
> > + */
> > +
> > +#include "pcie-designware.h"
> 
> You only need a forward declaration:
> 
> 	struct dw_pcie;
> 
> > +
> > +void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci);
> 
> Compile guard still missing.
> 

Perhaps we can just get rid of the Kconfig entry and build it by default for
both RC and EP drivers? I don't see a value in building it as a separate module.
And we may also move more common code in the future.

- Mani

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