[PATCH 1/2] dt-bindings: arm: bcm: raspberrypi,bcm2835-firmware: Add missing properties
Stefan Wahren
wahrenst at gmx.net
Tue Mar 26 10:40:52 PDT 2024
Am 26.03.24 um 18:18 schrieb Laurent Pinchart:
> On Tue, Mar 26, 2024 at 12:47:34PM +0100, Stefan Wahren wrote:
>> [add Dave since he's working on DMA for Raspberry Pi 4 and maybe have a
>> opinion about this]
>>
>> [drop Emma Anholt old address since she is not involved anymore]
>>
>> Am 26.03.24 um 08:06 schrieb Krzysztof Kozlowski:
>>> On 26/03/2024 01:49, Laurent Pinchart wrote:
>>>> The raspberrypi,bcm2835-firmware devices requires a dma-ranges property,
>>>> and, as a result, also needs to specify #address-cells and #size-cells.
>>>> Those properties have been added to thebcm2835-rpi.dtsi in commits
>>>> be08d278eb09 ("ARM: dts: bcm283x: Add cells encoding format to firmware
>>>> bus") and 55c7c0621078 ("ARM: dts: bcm283x: Fix vc4's firmware bus DMA
>>>> limitations"), but the DT bindings haven't been updated, resulting in
>>>> validation errors:
>>>>
>>>> arch/arm64/boot/dts/broadcom/bcm2711-rpi-4-b.dtb: firmware: '#address-cells', '#size-cells', 'dma-ranges', 'gpio' do not match any of the regexes: 'pinctrl-[0-9]+'
>>>> from schema $id: http://devicetree.org/schemas/arm/bcm/raspberrypi,bcm2835-firmware.yaml#
>>>>
>>>> Fix this by adding the properties to the bindings.
>>>>
>>>> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>>> Children do not perform any IO on their own, because everything is
>>> handled by parent. It is really odd to see dma-ranges without ranges.
>>> Referenced commits might be also wrong.
> Comunication with the firmware goes through a mailbox interface, which
> uses DMA transfers. See for instance
>
> rpi_firmware_transaction(struct rpi_firmware *fw, u32 chan, u32 data)
> {
> u32 message = MBOX_MSG(chan, data);
> int ret;
>
> WARN_ON(data & 0xf);
>
> mutex_lock(&transaction_lock);
> reinit_completion(&fw->c);
> ret = mbox_send_message(fw->chan, &message);
> if (ret >= 0) {
> if (wait_for_completion_timeout(&fw->c, HZ)) {
> ret = 0;
> } else {
> ret = -ETIMEDOUT;
> WARN_ONCE(1, "Firmware transaction timeout");
> }
> } else {
> dev_err(fw->cl.dev, "mbox_send_message returned %d\n", ret);
> }
> mutex_unlock(&transaction_lock);
>
> return ret;
> }
>
> int rpi_firmware_property_list(struct rpi_firmware *fw,
> void *data, size_t tag_size)
> {
> size_t size = tag_size + 12;
> u32 *buf;
> dma_addr_t bus_addr;
> int ret;
>
> /* Packets are processed a dword at a time. */
> if (size & 3)
> return -EINVAL;
>
> buf = dma_alloc_coherent(fw->cl.dev, PAGE_ALIGN(size), &bus_addr,
> GFP_ATOMIC);
> if (!buf)
> return -ENOMEM;
>
> /* The firmware will error out without parsing in this case. */
> WARN_ON(size >= 1024 * 1024);
>
> buf[0] = size;
> buf[1] = RPI_FIRMWARE_STATUS_REQUEST;
> memcpy(&buf[2], data, tag_size);
> buf[size / 4 - 1] = RPI_FIRMWARE_PROPERTY_END;
> wmb();
>
> ret = rpi_firmware_transaction(fw, MBOX_CHAN_PROPERTY, bus_addr);
>
> rmb();
> memcpy(data, &buf[2], tag_size);
> if (ret == 0 && buf[1] != RPI_FIRMWARE_STATUS_SUCCESS) {
> /*
> * The tag name here might not be the one causing the
> * error, if there were multiple tags in the request.
> * But single-tag is the most common, so go with it.
> */
> dev_err(fw->cl.dev, "Request 0x%08x returned status 0x%08x\n",
> buf[2], buf[1]);
> ret = -EINVAL;
> }
>
> dma_free_coherent(fw->cl.dev, PAGE_ALIGN(size), buf, bus_addr);
>
> return ret;
> }
>
> fw->cl.dev is the device for the firmware child node. That may be where
> the problem comes from, shouldn't we use the mailbox device for DMA
> mapping ?
>
From devicetree perspective this is the mailbox DT part [1] and this
the matching dt-binding [2].
[1] -
https://elixir.bootlin.com/linux/v6.9-rc1/source/arch/arm/boot/dts/broadcom/bcm283x.dtsi#L100
[2] -
https://elixir.bootlin.com/linux/v6.9-rc1/source/Documentation/devicetree/bindings/mailbox/brcm,bcm2835-mbox.yaml
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