| Message ID | 20230706043438.407600-1-a-verma1@ti.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] PCI: j721e: Delay 100ms T_PVPERL from power stable to PERST# inactive | expand |
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@ti.com> > --- > 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 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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 */ + extern const unsigned char pcie_link_speed[]; extern bool pci_early_dump;
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. 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. Fixes: f3e25911a430 ("PCI: j721e: Add TI J721E PCIe driver") Signed-off-by: Achal Verma <a-verma1@ti.com> --- drivers/pci/controller/cadence/pci-j721e.c | 11 +++++------ drivers/pci/pci.h | 2 ++ 2 files changed, 7 insertions(+), 6 deletions(-)