Re: [PATCH v3 2/2] PCI: rockchip-host: Wait 100ms after reset before starting configuration

[Damien Le Moal <dlemoal@kernel.org>]

On 4/13/24 06:29, Bjorn Helgaas wrote:
> On Fri, Apr 12, 2024 at 11:37:21AM +0900, Damien Le Moal wrote:
>> The PCI Express Base Specification r6.0, section 6.6.1, states that the
>> host should wait for at least 100 msec from the end of a conventional
>> reset (PERST# is de-asserted) before sending a configuration request to
>> ensure that the device is able to respond with a "Request Retry Status"
>> completion.
>>
>> Add the PCIE_T_RRS_READY_MS macro to define this wait time and modify
>> rockchip_pcie_host_init_port() to add this 100ms sleep after bringing
>> back PESRT# signal to high using the ep_gpio GPIO.
> 
> s/PESRT#/PERST#/
> s/bringing back PERST# signal to high/deasserting PERST#/
> 
>> Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
>> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
>> ---
>>  drivers/pci/controller/pcie-rockchip-host.c | 2 ++
>>  drivers/pci/pci.h                           | 7 +++++++
>>  2 files changed, 9 insertions(+)
>>
>> diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
>> index fc868251e570..cbec71114825 100644
>> --- a/drivers/pci/controller/pcie-rockchip-host.c
>> +++ b/drivers/pci/controller/pcie-rockchip-host.c
>> @@ -325,6 +325,8 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
>>  	msleep(PCIE_T_PVPERL_MS);
>>  	gpiod_set_value_cansleep(rockchip->ep_gpio, 1);
>>  
>> +	msleep(PCIE_T_RRS_READY_MS);
>> +
>>  	/* 500ms timeout value should be enough for Gen1/2 training */
>>  	err = readl_poll_timeout(rockchip->apb_base + PCIE_CLIENT_BASIC_STATUS1,
>>  				 status, PCIE_LINK_UP(status), 20,
>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
>> index 17fed1846847..c93ffc5e6e1f 100644
>> --- a/drivers/pci/pci.h
>> +++ b/drivers/pci/pci.h
>> @@ -16,6 +16,13 @@
>>  /* Power stable to PERST# inactive from PCIe card Electromechanical Spec */
>>  #define PCIE_T_PVPERL_MS		100
>>  
>> +/*
>> + * End of conventional reset (PERST# de-asserted) to first configuration
>> + * request (device able to respond with a "Request Retry Status" completion),
>> + * from PCI Express Base Specification r6.0, section 6.6.1.
> 
> "PCIe r6.0, sec 6.6.1" to match typical style, e.g., the reference
> just below.
> 
> Whoever applies this can take care of this.

To make it easier to apply, I sent v4 with the corrections. Thanks.

> 
>> +#define PCIE_T_RRS_READY_MS	100
> 
> Thanks a lot for doing this; there are many similar places we can
> update to use this #define.
> 
>>  /*
>>   * PCIe r6.0, sec 5.3.3.2.1 <PME Synchronization>
>>   * Recommends 1ms to 10ms timeout to check L2 ready.
>> -- 
>> 2.44.0
>>

-- 
Damien Le Moal
Western Digital Research


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