[PATCH] hwmon: xgene: access mailbox as RAM

Hoan Tran
2016-09-09T17:05:13Z

On Fri, Sep 9, 2016 at 9:58 AM, Guenter Roeck <linux@roeck-us.net> wrote:
> Hi Arnd,
>
> On Fri, Sep 09, 2016 at 05:38:58PM +0200, Arnd Bergmann wrote:
>> The newly added hwmon driver fails to build in an allmodconfig
>> kernel:
>>
>> 1 ERROR: "memblock_is_memory" [drivers/hwmon/xgene-hwmon.ko] undefined!
>>
>> According to comments in the code, the mailbox is a shared memory region,
>> not a set of MMIO registers, so we should use memremap() for mapping it
>> instead of ioremap or acpi_os_ioremap, and pointer dereferences instead
>> of readl/writel.
>>
>> The driver already uses plain kernel pointers, so it's a bit unusual
>> to work with functions that operate on __iomem pointers, and this
>> fixes that part too.
>>
>> I'm using READ_ONCE/WRITE_ONCE here to keep the existing behavior
>> regarding the ordering of the accesses from the CPU, but note that
>> there are no barriers (also unchanged from before).
>>
>> I'm also keeping the endianess behavior, though I'm unsure whether
>> the message data was supposed to be in LE32 format in the first
>> place, it's possible this was meant to be interpreted as a byte
>> stream instead.
>>
>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>
>
> Thanks a lot for looking into this.
>
> I'll apply this patch to address the build problem. Much better than
> my rude "depends on BROKEN". It would be great to get a Tested-by:
> from someone with access to the hardware.
>

Hi Arnd and Guenter,

Thanks for the patch. I'm testing it out.

Hoan

> Guenter
>
>> diff --git a/drivers/hwmon/xgene-hwmon.c b/drivers/hwmon/xgene-hwmon.c
>> index bc78a5d10182..e834dfb3acca 100644
>> --- a/drivers/hwmon/xgene-hwmon.c
>> +++ b/drivers/hwmon/xgene-hwmon.c
>> @@ -34,7 +34,8 @@
>> #include <linux/module.h>
>> #include <linux/of.h>
>> #include <linux/platform_device.h>
>> -#include <acpi/acpi_io.h>
>> +#include <linux/io.h>
>> +
>> #include <acpi/pcc.h>
>>
>> /* SLIMpro message defines */
>> @@ -126,10 +127,10 @@ static u16 xgene_word_tst_and_clr(u16 *addr, u16 mask)
>> {
>> u16 ret, val;
>>
>> - val = readw_relaxed(addr);
>> + val = le16_to_cpu(READ_ONCE(*addr));
>> ret = val & mask;
>> val &= ~mask;
>> - writew_relaxed(val, addr);
>> + WRITE_ONCE(*addr, cpu_to_le16(val));
>>
>> return ret;
>> }
>> @@ -137,7 +138,7 @@ static u16 xgene_word_tst_and_clr(u16 *addr, u16 mask)
>> static int xgene_hwmon_pcc_rd(struct xgene_hwmon_dev *ctx, u32 *msg)
>> {
>> struct acpi_pcct_shared_memory *generic_comm_base = ctx->pcc_comm_addr;
>> - void *ptr = generic_comm_base + 1;
>> + u32 *ptr = (void*)(generic_comm_base + 1);
>> int rc, i;
>> u16 val;
>>
>> @@ -146,21 +147,21 @@ static int xgene_hwmon_pcc_rd(struct xgene_hwmon_dev *ctx, u32 *msg)
>> ctx->resp_pending = true;
>>
>> /* Write signature for subspace */
>> - writel_relaxed(PCC_SIGNATURE_MASK | ctx->mbox_idx,
>> - &generic_comm_base->signature);
>> + WRITE_ONCE(generic_comm_base->signature,
>> + cpu_to_le32(PCC_SIGNATURE_MASK | ctx->mbox_idx));
>>
>> /* Write to the shared command region */
>> - writew_relaxed(MSG_TYPE(msg[0]) | PCCC_GENERATE_DB_INT,
>> - &generic_comm_base->command);
>> + WRITE_ONCE(generic_comm_base->command,
>> + cpu_to_le16(MSG_TYPE(msg[0]) | PCCC_GENERATE_DB_INT));
>>
>> /* Flip CMD COMPLETE bit */
>> - val = readw_relaxed(&generic_comm_base->status);
>> + val = le16_to_cpu(READ_ONCE(generic_comm_base->status));
>> val &= ~PCCS_CMD_COMPLETE;
>> - writew_relaxed(val, &generic_comm_base->status);
>> + WRITE_ONCE(generic_comm_base->status, cpu_to_le16(val));
>>
>> /* Copy the message to the PCC comm space */
>> for (i = 0; i < sizeof(struct slimpro_resp_msg) / 4; i++)
>> - writel_relaxed(msg[i], ptr + i * 4);
>> + WRITE_ONCE(ptr[i], cpu_to_le32(msg[i]));
>>
>> /* Ring the doorbell */
>> rc = mbox_send_message(ctx->mbox_chan, msg);
>> @@ -652,9 +653,9 @@ static int xgene_hwmon_probe(struct platform_device *pdev)
>> */
>> ctx->comm_base_addr = cppc_ss->base_address;
>> if (ctx->comm_base_addr) {
>> - ctx->pcc_comm_addr =
>> - acpi_os_ioremap(ctx->comm_base_addr,
>> - cppc_ss->length);
>> + ctx->pcc_comm_addr = memremap(ctx->comm_base_addr,
>> + cppc_ss->length,
>> + MEMREMAP_WT);
>> } else {
>> dev_err(&pdev->dev, "Failed to get PCC comm region\n");
>> rc = -ENODEV;
>>