Re: [PATCH 2/2] irqchip: irq-qcom-mpm: Support passing a slice of SRAM as reg space

Konrad Dybcio
2023-03-29T13:30:32Z

On 29.03.2023 15:28, Shawn Guo wrote:
> On Wed, Mar 29, 2023 at 01:06:11PM +0200, Konrad Dybcio wrote:
>>
>>
>> On 29.03.2023 05:49, Shawn Guo wrote:
>>> On Tue, Mar 28, 2023 at 12:02:53PM +0200, Konrad Dybcio wrote:
>>>> The MPM hardware is accessible to us from the ARM CPUs through a shared
>>>> memory region (RPM MSG RAM) that's also concurrently accessed by other
>>>> kinds of cores on the system (like modem, ADSP etc.). Modeling this
>>>> relation in a (somewhat) sane manner in the device tree basically
>>>> requires us to either present the MPM as a child of said memory region
>>>> (which makes little sense, as a mapped memory carveout is not a bus),
>>>> define nodes which bleed their register spaces into one another, or
>>>> passing their slice of the MSG RAM through some kind of a property.
>>>>
>>>> Go with the third option and add a way to map a region passed through
>>>> the "qcom,rpm-msg-ram" property as our register space.
>>>>
>>>> The current way of using 'reg' is preserved for ABI reasons.
>>>>
>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>>>> ---
>>>> drivers/irqchip/irq-qcom-mpm.c | 30 +++++++++++++++++++++++++-----
>>>> 1 file changed, 25 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/irqchip/irq-qcom-mpm.c b/drivers/irqchip/irq-qcom-mpm.c
>>>> index d30614661eea..6fe59f4deef4 100644
>>>> --- a/drivers/irqchip/irq-qcom-mpm.c
>>>> +++ b/drivers/irqchip/irq-qcom-mpm.c
>>>> @@ -14,6 +14,7 @@
>>>> #include <linux/mailbox_client.h>
>>>> #include <linux/module.h>
>>>> #include <linux/of.h>
>>>> +#include <linux/of_address.h>
>>>> #include <linux/of_device.h>
>>>> #include <linux/platform_device.h>
>>>> #include <linux/pm_domain.h>
>>>> @@ -322,8 +323,10 @@ static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
>>>> struct device *dev = &pdev->dev;
>>>> struct irq_domain *parent_domain;
>>>> struct generic_pm_domain *genpd;
>>>> + struct device_node *msgram_np;
>>>> struct qcom_mpm_priv *priv;
>>>> unsigned int pin_cnt;
>>>> + struct resource res;
>>>> int i, irq;
>>>> int ret;
>>>>
>>>> @@ -374,9 +377,21 @@ static int qcom_mpm_init(struct device_node *np, struct device_node *parent)
>>>>
>>>> raw_spin_lock_init(&priv->lock);
>>>>
>>>> - priv->base = devm_platform_ioremap_resource(pdev, 0);
>>>> - if (IS_ERR(priv->base))
>>>> - return PTR_ERR(priv->base);
>>>> + /* If we have a handle to an RPM message ram partition, use it. */
>>>> + msgram_np = of_parse_phandle(np, "qcom,rpm-msg-ram", 0);
>>>> + if (msgram_np) {
>>>> + ret = of_address_to_resource(msgram_np, 0, &res);
>>>> + /* Don't use devm_ioremap_resource, as we're accessing a shared region. */
>>>> + priv->base = ioremap(res.start, resource_size(&res));
>>>
>>> Are you suggesting that other cores/drivers will also need to access
>>> the mpm slice below?
>>>
>>> apss_mpm: sram@1b8 {
>>> reg = <0x1b8 0x48>;
>>> };
>> Yes, the RPM M3 core. Other slices may be accessed
>> by any core at any time.
>
> Hmm, let me reword my question. Other than irq-qcom-mpm, is there any
> other Linux drivers that also need to request this slice region?
No.

> Otherwise, I do not understand why devm_ioremap_resource() cannot be
> used.
drivers/rpmsg/qcom_glink_rpm.c calls devm_ioremap on the entire
RPM MSG RAM.

Konrad

>
> Shawn