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Date:   Mon, 01 Mar 2021 10:56:57 -0800
From:   Bhaumik Bhatt <bbhatt@codeaurora.org>
To:     Kalle Valo <kvalo@codeaurora.org>
Cc:     jhugo@codeaurora.org, linux-arm-msm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Gokul Sriram Palanisamy <gokulsri@codeaurora.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
        hemantk@codeaurora.org, sricharan@codeaurora.org,
        ath11k@lists.infradead.org
Subject: Re: [PATCH v2] bus: mhi: core: Add unique qrtr node id support
Organization: Qualcomm Innovation Center, Inc.
Reply-To: bbhatt@codeaurora.org
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Hi Kalle,

On 2021-03-01 10:26 AM, Kalle Valo wrote:
> Bhaumik Bhatt <bbhatt@codeaurora.org> writes:
> 
>> On 2021-03-01 03:14 AM, Kalle Valo wrote:
>>> + ath11k list
>>> 
>>> Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> writes:
>>> 
>>>> On Fri, Feb 26, 2021 at 04:12:49PM +0530, Gokul Sriram Palanisamy
>>>> wrote:
>>>>> On platforms with two or more identical mhi
>>>>> devices, qmi service will run with identical
>>>>> qrtr-node-id. Because of this identical ID,
>>>>> host qrtr-lookup cannot register more than one
>>>>> qmi service with identical node ID. Ultimately,
>>>>> only one qmi service will be avilable for the
>>>>> underlying drivers to communicate with.
>>>>> 
>>>>> On QCN9000, it implements a unique qrtr-node-id
>>>>> and qmi instance ID using a unique instance ID
>>>>> written to a debug register from host driver
>>>>> soon after SBL is loaded.
>>>>> 
>>>>> This change generates a unique instance ID from
>>>>> PCIe domain number and bus number, writes to the
>>>>> given debug register just after SBL is loaded so
>>>>> that it is available for FW when the QMI service
>>>>> is spawned.
>>>>> 
>>>>> sample:
>>>>> root@OpenWrt:/# qrtr-lookup
>>>>>   Service Version Instance Node  Port
>>>>>        15       1        0    8     1 Test service
>>>>>        69       1        8    8     2 ATH10k WLAN firmware service
>>>>>        15       1        0   24     1 Test service
>>>>>        69       1       24   24     2 ATH10k WLAN firmware service
>>>>> 
>>>>> Here 8 and 24 on column 3 (QMI Instance ID)
>>>>> and 4 (QRTR Node ID) are the node IDs that
>>>>> is unique per mhi device.
>>>>> 
>>>>> Signed-off-by: Gokul Sriram Palanisamy <gokulsri@codeaurora.org>
>>>>> ---
>>>>>  drivers/bus/mhi/core/boot.c | 14 ++++++++++++++
>>>>>  1 file changed, 14 insertions(+)
>>>>> 
>>>>> diff --git a/drivers/bus/mhi/core/boot.c
>>>>> b/drivers/bus/mhi/core/boot.c
>>>>> index c2546bf..5e5dad5 100644
>>>>> --- a/drivers/bus/mhi/core/boot.c
>>>>> +++ b/drivers/bus/mhi/core/boot.c
>>>>> @@ -16,8 +16,12 @@
>>>>>  #include <linux/random.h>
>>>>>  #include <linux/slab.h>
>>>>>  #include <linux/wait.h>
>>>>> +#include <linux/pci.h>
>>>>>  #include "internal.h"
>>>>> 
>>>>> +#define QRTR_INSTANCE_MASK	0x000000FF
>>>>> +#define QRTR_INSTANCE_SHIFT	0
>>>>> +
>>>>>  /* Setup RDDM vector table for RDDM transfer and program RXVEC */
>>>>>  void mhi_rddm_prepare(struct mhi_controller *mhi_cntrl,
>>>>>  		      struct image_info *img_info)
>>>>> @@ -391,6 +395,9 @@ void mhi_fw_load_handler(struct mhi_controller
>>>>> *mhi_cntrl)
>>>>>  	const struct firmware *firmware = NULL;
>>>>>  	struct image_info *image_info;
>>>>>  	struct device *dev = &mhi_cntrl->mhi_dev->dev;
>>>>> +	struct pci_dev *pci_dev = to_pci_dev(mhi_cntrl->cntrl_dev);
>>>>> +	struct pci_bus *bus = pci_dev->bus;
>>>>> +	uint32_t instance;
>>>>>  	const char *fw_name;
>>>>>  	void *buf;
>>>>>  	dma_addr_t dma_addr;
>>>>> @@ -466,6 +473,13 @@ void mhi_fw_load_handler(struct
>>>>> mhi_controller *mhi_cntrl)
>>>>>  		return;
>>>>>  	}
>>>>> 
>>>>> +	instance = ((pci_domain_nr(bus) & 0xF) << 4) | (bus->number & 
>>>>> 0xF);
>>>>> +	instance &= QRTR_INSTANCE_MASK;
>>>>> +
>>>>> +	mhi_write_reg_field(mhi_cntrl, mhi_cntrl->bhi,
>>>>> +			    BHI_ERRDBG2, QRTR_INSTANCE_MASK,
>>>>> +			    QRTR_INSTANCE_SHIFT, instance);
>>>> 
>>>> You cannot not do this in MHI stack. Why can't you do this in the
>>>> MHI controller
>>>> specific to QCN9000? And btw, is QCN9000 supported in mainline?
>>> 
>>> I'm not sure what QCN9000 means but I'm guessing it's QCN9074. We 
>>> have
>>> initial QCN9074 support in ath11k but there are some issues still so
>>> it's not enabled by default (yet):
>>> 
>>> https://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git/commit/?h=ath-next&id=4e80946197a83a6115e308334618449b77696d6a
>>> 
>>> And I suspect we have this same qrtr issue with any ath11k PCI 
>>> device,
>>> including QCA6390, so this is not a QCN9074 specific problem.
>>> 
>>> BTW Gokul, please always CC the ath11k list when submitting patches
>>> which are related to ath11k.
>> 
>> QRTR sits on top of MHI so shouldn't this be handled outside of MHI
>> after MHI is operational? We cannot allow PCI code in MHI core driver
>> but this can be handled pre or post MHI power-up in whatever way you
>> desire that does not have to directly involve MHI.
> 
> Sure, makes sense. I was just replying to Mani's question about status
> of QCN9000 upstream support.
> 
> So should we handle this within ath11k, is that the right approach? I
> also suspect that for QCN9074 and QCA6390 we have to do this a bit
> differently, so it would be easier to handle the differences between
> devices (and firmware versions) inside ath11k.

Yes, I feel it would be better handled within ath11k. AFAIK, device 
(QCA/QCN)
populates the BHI ERRDBG registers when it wants to communicate a 
certain
problem/status to the host and it should not be used the other way 
round,
where host writes a configuration cookie for the device to boot-up in a
particular way. It feels hacky as of now unless an actual configuration
register is used.

As per BHI specification, these registers are permitted to be read-only 
for
the host and Read/Write for device only. I also don't see any BHI
configuration or general purpose registers that can be used to notify 
this
cookie. If one is found, we can talk about how to use them and can 
introduce
MHI patches for those.

I suggest exploring alternatives to this. I think Hemant and are in 
agreement
on this.

Thanks,
Bhaumik
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