linux-kernel - Re: [PATCH v6 08/10] phy: qualcomm: phy-qcom-qmp-ufs: Add High Speed Gear 5 support for SM8550

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Date:   Thu, 30 Nov 2023 17:35:49 +0800
From:   Can Guo <quic_cang@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
CC:     <bvanassche@....org>, <adrian.hunter@...el.com>,
        <cmd4@...lcomm.com>, <beanhuo@...ron.com>, <avri.altman@....com>,
        <junwoo80.lee@...sung.com>, <martin.petersen@...cle.com>,
        <linux-scsi@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        "open list:GENERIC PHY FRAMEWORK" <linux-phy@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 08/10] phy: qualcomm: phy-qcom-qmp-ufs: Add High Speed
 Gear 5 support for SM8550



On 11/30/2023 5:34 PM, Manivannan Sadhasivam wrote:
> On Thu, Nov 30, 2023 at 04:49:12PM +0800, Can Guo wrote:
>>
>>
>> On 11/30/2023 4:38 PM, Manivannan Sadhasivam wrote:
>>> On Thu, Nov 30, 2023 at 04:14:25PM +0800, Can Guo wrote:
> 
> [...]
> 
>>>>>> +static int qmp_ufs_get_gear_overlay(struct qmp_ufs *qmp, const struct qmp_phy_cfg *cfg)
>>>>>> +{
>>>>>> +	u32 max_gear, floor_max_gear = cfg->max_supported_gear;
>>>>>> +	int i = NUM_OVERLAY - 1;
>>>>>
>>>>> Just use i directly in the for loop. Also, please rename "i" with "idx" to make
>>>>> it clear.
>>>>
>>>> OK
>>>>
>>>>>
>>>>>> +	int ret = -EINVAL;
>>>>>> +
>>>>>> +	for (; i >= 0; i --) {
>>>>>
>>>>> i--
>>>>>
>>>>>> +		max_gear = cfg->tbls_hs_overlay[i].max_gear;
>>>>>> +
>>>>>> +		if (max_gear == 0)
>>>>>> +			continue;
>>>>>
>>>>> You are setting max_gear even for targets with a single overlay. How can this
>>>>> become 0?
>>>>
>>>> Say 8550 has two overlays, 8450 has one overlay. We are sweeping all
>>>> overlays as NUM_OVERLAY == 2, so for 8450, there is one overlay initialized,
>>>> another one not initialized (max_gear == 0), we are skipping the one which
>>>> is not initialized.
>>>>
>>>
>>> This is confusing at its best :) Please check for the existence of the actual
>>> table instead. Like,
>>>
>>> 	for (idx = NUM_OVERLAY - 1; i >= 0, i--) {
>>>
>>> 		/* Skip if the table is not available */
>>> 		if (!cfg->tbls_hs_overlay[i].serdes)
>>> 			continue;
>>>
>>> 		...
>>> 	}
>>
>> We cannot expect overlay must has its own serdes, or tx/rx/pcs, hence I am
>> checking max_gear intead of any specific member.
>>
> 
> Hmm, then please add the comment as I suggested above.

Sure

Thanks,
Can Guo.

> 
>>>
>>>>>
>>>>>> +
>>>>>> +		/* Direct matching, bail */
>>>>>> +		if (qmp->submode == max_gear)
>>>>>> +			return i;
>>>>>> +
>>>>>> +		/* If no direct matching, the lowest gear is the best matching */
>>>>>> +		if (max_gear < floor_max_gear) {
>>>>>> +			ret = i;
>>>>>> +			floor_max_gear = max_gear;
>>>>>> +		}
>>>>>> +	}
>>>>>> +
>>>>>> +	return ret;
>>>>>> +}
>>>>>> +
>>>>>>     static void qmp_ufs_init_registers(struct qmp_ufs *qmp, const struct qmp_phy_cfg *cfg)
>>>>>>     {
>>>>>> +	int i;
>>>>>> +	bool apply_overlay = false;
>>>>>> +
>>>>>> +	i = qmp_ufs_get_gear_overlay(qmp, cfg);
>>>>>> +	if (i >= 0)
>>>>>> +		apply_overlay = true;
>>>>>
>>>>> How about?
>>>>>
>>>>> ```
>>>>> 	int idx;
>>>>>
>>>>> 	idx = qmp_ufs_get_gear_overlay(qmp, cfg);
>>>>>
>>>>> 	qmp_ufs_serdes_init(qmp, &cfg->tbls);
>>>>> 	qmp_ufs_lanes_init(qmp, &cfg->tbls);
>>>>> 	...
>>>>>
>>>>> 	if (idx >= 0) {
>>>>> 		qmp_ufs_serdes_init(qmp, &cfg->tbls_hs_overlay[idx]);
>>>>> 		qmp_ufs_lanes_init(qmp, &cfg->tbls_hs_overlay[idx]);
>>>>> 		...
>>>>> 	}
>>>>> ```
>>>>>
>>>>> Since the ordering doesn't matter for init sequence, you can program the overlay
>>>>> tables under a single condition.
>>>>
>>>> We can do that, but we need to be careful. When I say (in my previous reply)
>>>> the ordering does not matter, that saying is from the UFS PHY HPG doc.
>>>> However, in SW implementation, the 'tbls_hs_b' is actually overwriting one
>>>> COM_VCO_TUNE_MAP register, the same register is also programmed by common
>>>> table or overlay table. So qmp_ufs_serdes_init(qmp, &cfg->tbls_hs_b) should
>>>> come after overlays.
>>>>
>>>
>>> Then you can program tbls_hs_b after overlay tables. Wouldn't that work?
>>
>> I am programming tbls_hs_b after overlay tables, just a heads up in case you
>> are surprised :).
>>
> 
> Cool!
> 
> - Mani
>