RE: [PATCH v2 1/2] EDAC: add EDAC driver for DMC520

From: Lei Wang (BSP)
Date: Thu May 16 2019 - 16:05:07 EST

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Hi James/Borislav,

I addressed your comments and sent out " [PATCH v3 2/2] EDAC: add EDAC driver for DMC520" for review. Patch is against for-next.

More details please see inline below with "[Lei]" tag. Thanks!

-Lei

-----Original Message-----
From: James Morse <james.morse@xxxxxxx>
Sent: Monday, March 25, 2019 11:32 AM
To: Rui Zhao <ruizhao@xxxxxxxxxxx>
Cc: bp@xxxxxxxxx; robh+dt@xxxxxxxxxx; mark.rutland@xxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-edac@xxxxxxxxxxxxxxx; okaya@xxxxxxxxxx; mchehab@xxxxxxxxxx; will.deacon@xxxxxxx; sashal@xxxxxxxxxx; Hang Li <hangl@xxxxxxxxxxxxx>; Lei Wang (BSP) <Wang.Lei@xxxxxxxxxxxxx>; Rui Zhao <ruizhao@xxxxxxxxxxxxx>
Subject: Re: [PATCH v2 1/2] EDAC: add EDAC driver for DMC520

Hi Rui,

On 07/03/2019 01:24, Rui Zhao wrote:
> From: Rui Zhao <ruizhao@xxxxxxxxxxxxx> New driver supports error
> detection and correction on the devices with ARM DMC-520 memory
> controller.

> diff --git a/drivers/edac/dmc520_edac.c b/drivers/edac/dmc520_edac.c
> new file mode 100644 index 0000000..c70ce4e
> --- /dev/null
> +++ b/drivers/edac/dmc520_edac.c
> @@ -0,0 +1,619 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +// EDAC driver for DMC-520

[..]

> +// DMC-520 types, masks and bitfields
> +#define MEMORY_TYPE_LPDDR3 0
> +#define MEMORY_TYPE_DDR3 1
> +#define MEMORY_TYPE_DDR4 2
> +#define MEMORY_TYPE_LPDDR4 3

(this might be better as an enum as it hints to the compiler that only these values can ever happen. An example of where this is handy further down...)

> +#define MEMORY_DEV_WIDTH_X4 0
> +#define MEMORY_DEV_WIDTH_X8 1
> +#define MEMORY_DEV_WIDTH_X16 2
> +#define MEMORY_DEV_WIDTH_X32 3

(this might be better as an enum)

[Lei] We confirmed with Silicon Vendor the latest register definitions for type and dev width.

> +struct dmc520_edac {
> + void __iomem *reg_base;

> + char message[EDAC_MSG_BUF_SIZE];

Does there need to be an irq-safe lock for this mesage buffer?
Your snprintf() into it in dmc520_handle_dram_ecc_errors(), which is called from both
dmc520_edac_dram_ue_isr() and dmc520_edac_dram_ce_isr()... if these are wired up as different irqs, they could happen on different CPUs concurrently...

[Lei] We modified message to be allocated on stack.

> +};

> +static bool dmc520_get_dram_ecc_error_info(struct dmc520_edac *edac,
> + bool is_ce,
> + struct ecc_error_info *info)
> +{
> + u32 reg_offset_low, reg_offset_high;
> + u32 reg_val_low, reg_val_high;
> + bool valid;
> +
> + reg_offset_low = is_ce ? REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_31_00 :
> + REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_31_00;
> + reg_offset_high = is_ce ? REG_OFFSET_DRAM_ECC_ERRC_INT_INFO_63_32 :
> + REG_OFFSET_DRAM_ECC_ERRD_INT_INFO_63_32;
> +
> + reg_val_low = dmc520_read_reg(edac, reg_offset_low);
> + reg_val_high = dmc520_read_reg(edac, reg_offset_high);
> +
> + valid = (FIELD_GET(REG_FIELD_ERR_INFO_LOW_VALID, reg_val_low) != 0) &&
> + (FIELD_GET(REG_FIELD_ERR_INFO_HIGH_VALID, reg_val_high) != 0);
> +
> + if (info) {

I see one caller, dmc520_handle_dram_ecc_errors(), which has info on the stack... is it possible for info to be NULL here?

[Lei] This is not changed since it's fine to check NULL here.

> + if (valid) {
> + info->col = FIELD_GET(REG_FIELD_ERR_INFO_LOW_COL,
> + reg_val_low);
> + info->row = FIELD_GET(REG_FIELD_ERR_INFO_LOW_ROW,
> + reg_val_low);
> + info->rank = FIELD_GET(REG_FIELD_ERR_INFO_LOW_RANK,
> + reg_val_low);
> + info->bank = FIELD_GET(REG_FIELD_ERR_INFO_HIGH_BANK,
> + reg_val_high);
> + } else {
> + memset(info, 0, sizeof(struct ecc_error_info));
> + }
> + }
> +
> + return valid;
> +}

> +static enum mem_type dmc520_get_mtype(struct dmc520_edac *edac) {
> + enum mem_type mt;
> + u32 reg_val, type;
> +
> + reg_val = dmc520_read_reg(edac, REG_OFFSET_MEMORY_TYPE_NOW);
> + type = FIELD_GET(REG_FIELD_MEMORY_TYPE, reg_val);
> +
> + switch (type) {
> + case MEMORY_TYPE_LPDDR3:
> + case MEMORY_TYPE_DDR3:
> + mt = MEM_DDR3;
> + break;
> +
> + case MEMORY_TYPE_DDR4:
> + case MEMORY_TYPE_LPDDR4:
> + default:

Is this default just to shut the compiler warning up?
If so, you could use an enum and the compiler won't warn for a switch() that has all the cases covered.

[Lei] This was addressed in new PATCH.

> + mt = MEM_DDR4;
> + break;
> + }
> + return mt;
> +}

> +static irqreturn_t dmc520_edac_dram_ce_isr(int irq, void *data) {
> + return dmc520_edac_dram_ecc_isr(irq, data, true); }
> +
> +static irqreturn_t dmc520_edac_dram_ue_isr(int irq, void *data) {
> + return dmc520_edac_dram_ecc_isr(irq, data, false); }

How come these calls aren't folded into the one-size fits all irq handler below?
If the hardware always sets the status register, does the irqchip driver need to call a different helper?

[Lei] I refactored the way how isr is registered. Now there is a one-to-one mapping from each interrupt line
to its supported interrupt-mask. It's more flexible to adapt to other possible platform implementations for future.

> +static irqreturn_t dmc520_edac_all_isr(int irq, void *data) {
> + struct mem_ctl_info *mci;
> + struct dmc520_edac *edac;
> + u32 status;
> +
> + mci = data;
> + edac = mci->pvt_info;
> +
> + status = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_STATUS);
> +
> + if (status & DRAM_ECC_INT_CE_MASK)
> + dmc520_edac_dram_ce_isr(irq, data);
> +
> + if (status & DRAM_ECC_INT_UE_MASK)
> + dmc520_edac_dram_ue_isr(irq, data);
> +
> + // Other interrupt handlers can be added
> +
> + return IRQ_HANDLED;

Shouldn't there be a way of getting IRQ_NONE out of this?

[Lei] Addressed.

> +}

[...]

> +static int count_set_bits(u32 n)
> +{
> + int count;
> +
> + for (count = 0; n != 0; n &= (n - 1))
> + count++;
> +
> + return count;
> +}

Isn't this what hweight() does?

[Lei] Addressed.

> +static int dmc520_edac_probe(struct platform_device *pdev) {
> + struct device *dev;
> + struct dmc520_edac *edac;
> + struct mem_ctl_info *mci;
> + struct edac_mc_layer layers[1];
> + int ret, irq, nintr;
> + struct resource *res;
> + void __iomem *reg_base;
> + u32 status, current_bit, interrupt_mask;
> + bool interrupt_shared;
> +
> + dev = &pdev->dev;
> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + reg_base = devm_ioremap_resource(dev, res);
> + if (IS_ERR(reg_base))
> + return PTR_ERR(reg_base);
> +
> + layers[0].type = EDAC_MC_LAYER_CHIP_SELECT;
> + layers[0].size = dmc520_get_rank_count(reg_base);
> + layers[0].is_virt_csrow = true;
> +
> + mci = edac_mc_alloc(dmc520_mc_idx++, ARRAY_SIZE(layers), layers,
> + sizeof(struct dmc520_edac));
> + if (!mci) {
> + edac_printk(KERN_ERR, EDAC_MOD_NAME,
> + "Failed to allocate memory for mc instance\n");
> + return -ENOMEM;
> + }
> +
> + edac = mci->pvt_info;
> + edac->reg_base = reg_base;
> +
> + if (!dmc520_is_ecc_enabled(edac)) {
> + edac_printk(KERN_ERR, EDAC_MOD_NAME, "ECC not enabled\n");
> + ret = -ENXIO;
> + goto err;
> + }
> +
> + platform_set_drvdata(pdev, mci);
> +
> + mci->pdev = dev;
> + mci->mtype_cap = MEM_FLAG_DDR3 | MEM_FLAG_DDR4;
> + mci->edac_ctl_cap = EDAC_FLAG_NONE | EDAC_FLAG_SECDED;
> + mci->edac_cap = EDAC_FLAG_SECDED;
> + mci->scrub_cap = SCRUB_FLAG_HW_SRC;
> + mci->scrub_mode = dmc520_is_scrub_configured(edac) ?
> + SCRUB_HW_SRC : SCRUB_NONE;
> + mci->ctl_name = EDAC_CTL_NAME;
> + mci->dev_name = dev_name(mci->pdev);
> + mci->mod_name = EDAC_MOD_NAME;
> + mci->ctl_page_to_phys = NULL;
> +
> + edac_op_state = EDAC_OPSTATE_INT;
> +
> + dmc520_init_csrow(mci);
> +
> + ret = edac_mc_add_mc(mci);
> + if (ret) {
> + edac_printk(KERN_ERR, EDAC_MOD_NAME,
> + "Failed to register with EDAC core\n");
> + goto err;
> + }
> +
> + interrupt_shared = false;
> + interrupt_mask = DRAM_ECC_INT_CE_MASK | DRAM_ECC_INT_UE_MASK;
> +
> + if (dev->of_node) {
> + if (of_find_property(dev->of_node, "interrupt-shared", NULL))
> + interrupt_shared = true;
> +
> + if (of_property_read_u32(dev->of_node,
> + "interrupt-mask",
> + &interrupt_mask)) {
> + edac_printk(KERN_INFO, EDAC_MOD_NAME,
> + "Use default interrupt mask 0x%X\n",
> + interrupt_mask);
> + }
> +
> + interrupt_mask &= ALL_INT_MASK;
> + }
> +
> + // Clear interrupts
> + status = dmc520_read_reg(edac, REG_OFFSET_INTERRUPT_STATUS);
> + dmc520_write_reg(edac, 0, REG_OFFSET_INTERRUPT_CONTROL);
> + dmc520_write_reg(edac, ALL_INT_MASK, REG_OFFSET_INTERRUPT_CLR);
> +
> + // Reset DRAM CE/UE counters
> + if (interrupt_mask & DRAM_ECC_INT_CE_MASK)
> + dmc520_get_dram_ecc_error_count(edac, true);
> +
> + if (interrupt_mask & DRAM_ECC_INT_UE_MASK)
> + dmc520_get_dram_ecc_error_count(edac, false);
> +
> + nintr = count_set_bits(interrupt_mask);
> + if (nintr == 0) {
> + edac_printk(KERN_ERR, EDAC_MC,
> + "Invalid interrupt mask 0x%X\n",
> + interrupt_mask);
> + ret = -EINVAL;
> + goto err;

This is after edac_mc_add_mc(), and on your remove path you have a edac_mc_del_mc(). Is that necessary here? Do you need an err_del_mc?

[Lei] Addressed.

> + }
> +
> + current_bit = BIT(0);
> + for (irq = 0; irq < nintr; ++irq) {
> + irq_handler_t edac_isr;
> + int irq_id = platform_get_irq(pdev, irq);
> +
> + if (irq_id < 0) {
> + edac_printk(KERN_ERR, EDAC_MC,
> + "Failed to get %s irq\n",
> + irq == 0 ? "CE" : "UE");
> + ret = -ENODEV;
> + goto err;

err_del_mc?

> + }
> +
> + if (interrupt_shared) {
> + edac_isr = dmc520_edac_all_isr;
> + } else {
> + while (current_bit & ALL_INT_MASK) {
> + if (current_bit & interrupt_mask)
> + break;
> +
> + current_bit <<= 1;
> + }
> +
> + if (current_bit & DRAM_ECC_INT_CE_MASK) {
> + edac_isr = dmc520_edac_dram_ce_isr;
> + } else if (current_bit & DRAM_ECC_INT_UE_MASK) {
> + edac_isr = dmc520_edac_dram_ue_isr;
> + } else {
> + edac_printk(KERN_ERR, EDAC_MC,
> + "Invalid interrupt bit 0x%X\n",
> + current_bit);
> + ret = -EINVAL;
> + goto err;

err_del_mc?

> + }
> +
> + current_bit <<= 1;
> + }
> +
> + ret = devm_request_irq(&pdev->dev,
> + irq_id,
> + edac_isr,
> + 0,
> + dev_name(&pdev->dev),
> + mci);
> + if (ret < 0) {
> + edac_printk(KERN_ERR, EDAC_MC,
> + "Failed to request irq %d\n", irq_id);
> + goto err;

err_del_mc?

> + }
> +
> + // Only one irq for all interrupts
> + if (interrupt_shared)
> + break;
> + }
> +
> + // Enable interrupts
> + dmc520_write_reg(edac, interrupt_mask,
> +REG_OFFSET_INTERRUPT_CONTROL);
> +
> + return 0;
> +
> +err:
> + edac_mc_free(mci);
> +
> + return ret;
> +}

[...]

> +MODULE_AUTHOR("Rui Zhao <ruizhao@xxxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("DMC-520 ECC driver");

> +MODULE_LICENSE("GPL v2");

This doesn't match your SPDX tag above:
| // SPDX-License-Identifier: GPL-2.0+

Can I use a later version?

[Lei] Addressed

Thanks,

James

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