From: Mukesh Ojha <quic_mojha@quicinc.com>
To: Pavan Kondeti <quic_pkondeti@quicinc.com>
Cc: Bjorn Andersson <andersson@kernel.org>,
<konrad.dybcio@linaro.org>, <linux-arm-msm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linus.walleij@linaro.org>,
<linux-gpio@vger.kernel.org>
Subject: Re: [PATCH v12 7/9] firmware: qcom: scm: Fix __scm->dev assignement
Date: Tue, 19 Mar 2024 15:38:57 +0530 [thread overview]
Message-ID: <fce3beb8-7d70-672c-e25b-d46810c4d1dd@quicinc.com> (raw)
In-Reply-To: <03367100-1ad4-4d83-8200-5879550398be@quicinc.com>
On 3/19/2024 6:47 AM, Pavan Kondeti wrote:
> On Mon, Mar 18, 2024 at 06:38:20PM +0530, Mukesh Ojha wrote:
>>
>>
>> On 3/3/2024 12:55 AM, Bjorn Andersson wrote:
>>> On Tue, Feb 27, 2024 at 09:23:06PM +0530, Mukesh Ojha wrote:
>>>> qcom_scm_is_available() gives wrong indication if __scm
>>>> is initialized but __scm->dev is not.
>>>>
>>>> Fix this appropriately by making sure if __scm is
>>>> initialized and then it is associated with its
>>>> device.
>>>>
>>>
>>> This seems like a bug fix, and should as such have a Fixes: tag and
>>> probably Cc: stable@vger.kernel.org
>>>
>>>> Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
>>>> ---
>>>> drivers/firmware/qcom/qcom_scm.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/firmware/qcom/qcom_scm.c b/drivers/firmware/qcom/qcom_scm.c
>>>> index 6c252cddd44e..6f14254c0c10 100644
>>>> --- a/drivers/firmware/qcom/qcom_scm.c
>>>> +++ b/drivers/firmware/qcom/qcom_scm.c
>>>> @@ -1859,6 +1859,7 @@ static int qcom_scm_probe(struct platform_device *pdev)
>>>> if (!scm)
>>>> return -ENOMEM;
>>>> + scm->dev = &pdev->dev;
>>>> ret = qcom_scm_find_dload_address(&pdev->dev, &scm->dload_mode_addr);
>>>> if (ret < 0)
>>>> return ret;
>>>> @@ -1895,7 +1896,6 @@ static int qcom_scm_probe(struct platform_device *pdev)
>>>> return ret;
>>>> __scm = scm;
>>>> - __scm->dev = &pdev->dev;
>>>
>>> Is it sufficient to just move the line up, or do we need a barrier of
>>> some sort here?
>>
>> Would be good to use, smp_mb() before the assignment
>> __scm = scm
>> along with moving below line
>> __scm->dev = &pdev->dev
>>
>
> Full memory barrier is not needed here. store variant is sufficient.
> WRITE_ONCE() + smp_store_release() will fit here no?
Thanks for the comment, i again have a look at it and agree we don't
need a full barrier here.
And we can do either of the below two ways.
-Mukesh
// 1st way
diff --git a/drivers/firmware/qcom/qcom_scm.c
b/drivers/firmware/qcom/qcom_scm.c
index 49ddbcab0680..b638fb407fc6 100644
--- a/drivers/firmware/qcom/qcom_scm.c
+++ b/drivers/firmware/qcom/qcom_scm.c
@@ -1741,7 +1741,12 @@ static int qcom_scm_qseecom_init(struct qcom_scm
*scm)
*/
bool qcom_scm_is_available(void)
{
- return !!__scm;
+ bool avail;
*/
bool qcom_scm_is_available(void)
{
- return !!__scm;
+ bool avail;
+
+ avail = !!READ_ONCE(__scm);
+ smp_rmb();
+
+ return avail;
}
EXPORT_SYMBOL_GPL(qcom_scm_is_available);
@@ -1822,10 +1827,12 @@ static int qcom_scm_probe(struct platform_device
*pdev)
if (!scm)
return -ENOMEM;
+ scm->dev = &pdev->dev;
ret = qcom_scm_find_dload_address(&pdev->dev,
&scm->dload_mode_addr);
if (ret < 0)
return ret;
+ init_completion(&scm->waitq_comp);
mutex_init(&scm->scm_bw_lock);
scm->path = devm_of_icc_get(&pdev->dev, NULL);
@@ -1857,10 +1864,8 @@ static int qcom_scm_probe(struct platform_device
*pdev)
if (ret)
return ret;
- __scm = scm;
- __scm->dev = &pdev->dev;
-
- init_completion(&__scm->waitq_comp);
+ smp_wmb();
+ WRITE_ONCE(__scm, scm);
// 2nd way
diff --git a/drivers/firmware/qcom/qcom_scm.c
b/drivers/firmware/qcom/qcom_scm.c
index 49ddbcab0680..911699123f9f 100644
--- a/drivers/firmware/qcom/qcom_scm.c
+++ b/drivers/firmware/qcom/qcom_scm.c
@@ -1741,7 +1741,7 @@ static int qcom_scm_qseecom_init(struct qcom_scm *scm)
*/
bool qcom_scm_is_available(void)
{
- return !!__scm;
+ return !!smp_load_acquire(&__scm);
}
EXPORT_SYMBOL_GPL(qcom_scm_is_available);
@@ -1822,10 +1822,12 @@ static int qcom_scm_probe(struct platform_device
*pdev)
if (!scm)
return -ENOMEM;
+ scm->dev = &pdev->dev;
ret = qcom_scm_find_dload_address(&pdev->dev, &scm->dload_mode_addr);
if (ret < 0)
return ret;
+ init_completion(&scm->waitq_comp);
mutex_init(&scm->scm_bw_lock);
scm->path = devm_of_icc_get(&pdev->dev, NULL);
@@ -1857,10 +1859,8 @@ static int qcom_scm_probe(struct platform_device
*pdev)
if (ret)
return ret;
- __scm = scm;
- __scm->dev = &pdev->dev;
-
- init_completion(&__scm->waitq_comp);
+ /* Let all above stores available after this. */
+ smp_store_release(&__scm, scm);
irq = platform_get_irq_optional(pdev, 0);
if (irq < 0) {
--
2.7.4
>
> Thanks,
> Pavan
next prev parent reply other threads:[~2024-03-19 10:09 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-27 15:52 [PATCH v12 0/9] Misc SCM driver changes Mukesh Ojha
2024-02-27 15:53 ` [PATCH v12 1/9] firmware: qcom: scm: Rename scm_query_lock to scm_lock Mukesh Ojha
2024-03-02 19:10 ` Bjorn Andersson
2024-02-27 15:53 ` [PATCH v12 2/9] firmware: qcom: scm: provide a read-modify-write function Mukesh Ojha
2024-03-02 19:09 ` Bjorn Andersson
2024-03-05 10:39 ` Mukesh Ojha
2024-02-27 15:53 ` [PATCH v12 3/9] firmware: qcom: scm: Modify only the download bits in TCSR register Mukesh Ojha
2024-03-02 19:13 ` Bjorn Andersson
2024-03-05 10:43 ` Mukesh Ojha
2024-02-27 15:53 ` [PATCH v12 4/9] firmware: qcom: scm: Rework dload mode availability check Mukesh Ojha
2024-03-02 19:16 ` Bjorn Andersson
2024-03-05 10:54 ` Mukesh Ojha
2024-02-27 15:53 ` [PATCH v12 5/9] pinctrl: qcom: Use qcom_scm_io_rmw() function Mukesh Ojha
2024-02-29 13:56 ` Linus Walleij
2024-02-27 15:53 ` [PATCH v12 6/9] firmware: qcom: scm: Remove log reporting memory allocation failure Mukesh Ojha
2024-03-02 19:18 ` Bjorn Andersson
2024-02-27 15:53 ` [PATCH v12 7/9] firmware: qcom: scm: Fix __scm->dev assignement Mukesh Ojha
2024-03-02 19:25 ` Bjorn Andersson
2024-03-18 13:08 ` Mukesh Ojha
2024-03-19 1:17 ` Pavan Kondeti
2024-03-19 10:08 ` Mukesh Ojha [this message]
2024-03-19 10:22 ` Pavan Kondeti
2024-03-19 14:39 ` Mukesh Ojha
2024-02-27 15:53 ` [PATCH v12 8/9] firmware: qcom: scm: Add check to prevent Null pointer dereference Mukesh Ojha
2024-02-27 16:56 ` Elliot Berman
2024-02-28 15:08 ` Mukesh Ojha
2024-03-01 23:42 ` Konrad Dybcio
2024-03-02 18:57 ` Bjorn Andersson
2024-02-27 15:53 ` [PATCH v12 9/9] firmware: scm: Remove redundant scm argument from qcom_scm_waitq_wakeup() Mukesh Ojha
2024-03-02 19:23 ` Bjorn Andersson
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