On Thu, Jul 06, 2023 at 10:04:38AM +0530, Achal Verma wrote:
> As per the PCIe Card Electromechanical specification REV. 5.0, PERST#
> signal should be de-asserted after minimum 100ms from the time power-rails
> become stable.
> So, to ensure 100ms delay to give sufficient time for power-rails and
> refclk to become stable, change delay from 100us to 100ms.
Looks like the above is intended to be two paragraphs. Add a blank
line between, or rewrap into a single paragraph if you prefer that.
> From PCIe Card Electromechanical specification REV. 5.0 section 2.9.2:
> TPVPERL: Power stable to PERST# inactive - 100ms
> T-PERST-CLK: REFCLK stable before PERST# inactive - 100 usec.
Is T-PERST-CLK relevant here? Omit if not.
> Fixes: f3e25911a430 ("PCI: j721e: Add TI J721E PCIe driver")
> Signed-off-by: Achal Verma <a-verma1@xxxxxx>
> ---
> drivers/pci/controller/cadence/pci-j721e.c | 11 +++++------
> drivers/pci/pci.h | 2 ++
> 2 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
> index e70213c9060a..a3c8273b7320 100644
> --- a/drivers/pci/controller/cadence/pci-j721e.c
> +++ b/drivers/pci/controller/cadence/pci-j721e.c
> @@ -498,14 +498,13 @@ static int j721e_pcie_probe(struct platform_device *pdev)
>
> /*
> * "Power Sequencing and Reset Signal Timings" table in
> - * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 3.0
> - * indicates PERST# should be deasserted after minimum of 100us
> - * once REFCLK is stable. The REFCLK to the connector in RC
> - * mode is selected while enabling the PHY. So deassert PERST#
> - * after 100 us.
> + * PCI EXPRESS CARD ELECTROMECHANICAL SPECIFICATION, REV. 5.0
> + * indicates PERST# should be deasserted after minimum of 100ms
> + * after power rails achieve specified operating limits and
> + * within this period reference clock should also become stable.
> */
> if (gpiod) {
> - usleep_range(100, 200);
> + msleep(PCI_TPVPERL_DELAY);
> gpiod_set_value_cansleep(gpiod, 1);
> }
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index a4c397434057..7482cff16fef 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -13,6 +13,8 @@
>
> #define PCIE_LINK_RETRAIN_TIMEOUT_MS 1000
>
> +#define PCI_TPVPERL_DELAY 100 /* msec; see PCIe r5.0, sec 2.9.2 */
Perhaps make the name "PCIE_..." since this is a PCIe-specific time.
Also add "_MS" to the name so it's easy to verify that users are using
the correct mechanism (usleep/msleep/etc).
Otherwise looks good to me, thanks!
> extern const unsigned char pcie_link_speed[];
> extern bool pci_early_dump;
>
> --
> 2.25.1
>
>
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